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Using the WebLogic JDBC t3 Driver
I. IntroductionOverview of WebLogic JDBCWebLogic JDBC, WebLogic's multitier JDBC implementation (based on JavaSoft's JDBC
specification), gives applets
and applications database access from within WebLogic. WebLogic
supports multiple multitier server products that provide various
services, one of which is database access with WebLogic JDBC.
Because WebLogic JDBC is Java-only, that is, it uses no native methods
A WebLogic JDBC applet or application acts as a client of the
WebLogic Server
WebLogic JDBC requires a JDBC driver between the WebLogic Server and
the database server. You can use the WebLogic two-tier driver,
WebLogic jDriver for Oracle. You may also elect to use any
other JDBC driver, including a JDBC driver for ODBC Setting classpath when starting WebLogic ServerWhen you use a two-tier JDBC driver to connect to a database through one of the WebLogic Server's multitier drivers (t3, pool, or jts), you must start the server with the classes of the JDBC driver appended to the WebLogic classpath, specified with the weblogic.class.path property on the command line when starting WebLogic Server.Please see WebLogic Platform Support for a table of the DBMS versions, client library versions, and operating systems supported by the WebLogic jDriver JDBC drivers.
WebLogic JDBC architectureWebLogic JDBC's architecture is defined by its place in the WebLogic framework as part of WebLogic's multitier environment. The WebLogic JDBC Server sits between the WebLogic JDBC application and the remote DBMSes that it accesses. The WebLogic JDBC application is a client of the WebLogic Server, and the WebLogic Server becomes a client of the DBMS. There are two sides to this relationship that are important to understand:Between the WebLogic Server and its WebLogic JDBC clients. Each WebLogic JDBC client has its own context, or Workspace, within WebLogic. The protocol between the WebLogic Server and its clients is a multiplexed, bidirectional, asynchronous connection. The connection between any T3Client and the WebLogic Server is a "rich-socket connection;" that means that the connection carries much more information than a TCP socket connection does. Internally, the WebLogic Server uses an efficient packet-based queuing protocol. For more information about the relationship between T3Clients and the WebLogic Server, see the Developers Guide, Writing a T3Client application. Between the WebLogic Server and the DBMS. Using a JDBC driver and vendor libraries, the WebLogic Server maintains a connection to one or more databases on behalf of the T3Client. The WebLogic Server communicates with remote DBMS via JDBC drivers and, depending upon the JDBC driver, a vendor-specific library or ODBC. We talk about this connection between the WebLogic Server and the DBMS as the "two-tier connection." The WebLogic Server may be connected to more than one database for requests from a single client; and the WebLogic Server may be connected to only one database for requests from multiple clients. There is also a fundamental relationship between a WebLogic JDBC client and the databases that it accesses, with the WebLogic Server in the middle. This relationship is defined by a JDBC Connection object. There are several ways to create and use JDBC Connections; a WebLogic JDBC client can create a JDBC Connection by setting up certain properties, identifying the right JDBC drivers, and making a connection. A JDBC Connection object can be cached (saved) in the T3Client's Workspace on the WebLogic Server. JDBC Connections can also be created when the WebLogic Server starts up, as a pool of connections available to one or more clients.
The WebLogic Server has many features that can enhance a JDBC application, but all that is required of a WebLogic JDBC application is to connect to a WebLogic Server at the beginning of the session and disconnect at the end. The connection between the WebLogic Server and the DBMS is handled transparently. Using third-party JDBC 2.0 drivers in a multitier configurationYou may use third-party JDBC 2.0 drivers with WebLogic JDBC and WebLogic Server. Such use requires that you run WebLogic Server or WebLogic JDBC under Java 2 (JDK 1.2.x). There are currently limitations regarding the use of Java 2 that you should consider when using JDBC 2.0 drivers. These limitations are discussed on the WebLogic platforms page.When you use a third-party JDBC 2.0 driver in a multitier configuration, all of the driver's calls and the returned data are transparently passed through the WebLogic multitier driver. This allows you to use any functionality available in that driver in a WebLogic multitier configuration. To use a JDBC 2.0 driver in a multitier configuration, make the following changes in your code:
II. The WebLogic JDBC APIAPI ReferenceWebLogic provides extensions to JDBC for certain WebLogic JDBC enhancements (some support WebLogic jDriver JDBC extensions in a multitier environment). See the API Reference for links to the API (Javadoc) documentation for these extensions.
WebLogic JDBC objects and their classesWebLogic JDBC implements JDBC (current version is 1.22). The JDBC implementation is not covered in this developer guide. However, we do provide JavaSoft's classdocs (API reference materials) along with our other online reference. Anyone can freely download the JDBC classes and API documentation; go to JavaSoft. Documented here are those objects and classes specific to WebLogic JDBC's use in the WebLogic framework. The classes that you import in WebLogic JDBC applications include:
Other classes
Upgrading to JDK 1.1x
With WebLogic release 3.0, you should have upgraded your use of
WebLogic JDBC to the latest release of the 1.1 version of the Java
Developers Kit A significant change between the 1.0.2 and 1.1 versions of the JDK is that the JDBC classes (java.sql.*) are included in the JDK 1.1. The temporary set of JDBC classes that WebLogic provided -- xjava.sql.* and weblogic.db.xjdbc.* -- are no longer necessary for use with JDK 1.1. How to upgrade
Steps to building a WebLogic JDBC application are covered here. The simple application that is used in the full code example makes a connection to an Oracle database via a WebLogic Server, inserts, updates, and deletes a series of records, and creates and uses stored procedures and functions. Other examples included in the step-by-step discussion show similar code for use with a Sybase database, particularly in the section on stored procedures and functions. The first five steps are covered in the order in which they should appear in an application, and are numbered accordingly.
A full code example for using an Oracle database with WebLogic JDBC is reproduced at the end of this document. It incorporates many of the code examples used in the step-by-step instructions. If you are using a WebLogic jDriver two-tier driver between the WebLogic Server and the DBMS, you should also check the Developers Guides for the particular two-tier driver you are using. For a listing, see WebLogic JDBC Options. Step 1. Importing packagesImport the following into your WebLogic JDBC application:
Declare the Connection object at the top of your method, since it is used in the try and the finally blocks. Also, declare the T3Client object before the try block unless you will be using an embedded T3Client. Added as a feature in release 2.3.2, an embedded T3Client is set up by adding another property to the java.util.Properties object. An embedded T3Client is constructed and connected automatically, and can be used in any WebLogic JDBC class where you do not need an explicit T3Client object for other operations. For more on using explicit or embedded T3Clients, see Creating the T3Client.
Step 2. Creating the T3ClientUsing an explicit or an embedded T3ClientIn general, each WebLogic JDBC application begins with the creation of a T3Client object. (A T3Client may be created automatically for you, if you use the embedded T3Client feature available in release 2.3.2 and after.) The T3Client becomes the client context for this client within a WebLogic Server and uniquely identifies the client and its requests. A T3Client also owns its Workspace inside the WebLogic Server which persists and allows a T3Client to reconstitute itself for successive WebLogic Server sessions. For WebLogic JDBC applications, the T3Client is also one of the properties passed to the constructor for the JDBC Connection. The T3Client class, weblogic.common.T3Client, contains constructors and several methods that we use in WebLogic JDBC. You can create a new T3Client, or you can reconstitute a previously created Workspace and return the T3client to the state in which you left it. A client's Workspace includes access to a set of cached JDBC connections that are set aside in the WebLogic Server for a group of WebLogic JDBC Clients. All T3Client constructors require at least one argument, which is the URL of the WebLogic Server and (optionally, if the port is not 80) the TCP port at which the WebLogic Server is listening for T3Client connection requests. The URL is expressed after the format: accessProtocol://WebLogicServerURL:port The accessProtocol may be any of the protocols described in Writing a T3Client application, including t3 (standard T3Client access over a high-performance, multiplexed, asynchronous, bidirectional connection), t3s (T3Client access authenticated and/or encrypted with SSL), or http (T3Client access over HTTP tunneling, for transfirewall access). The WebLogicServerURL is determined by whatever method is appropriate on that machine. The port is the port at which the WebLogic Server is listening for T3Client login requests. Here is an example of constructing a T3Client: T3Client t3 = null;
try {
t3 = new T3Client("t3://bigbox:7001");
Each T3Client has a Workspace inside the WebLogic Server into which it can save its context and revisit at a later time. You can even name the T3Client's Workspace at the time you create the T3Client, which offers an easy way to revisit the Workspace; or you can get the default T3Client's Workspace after the T3Client connects. Workspaces are powerful models for creating integrated business applications; read more about Workspaces in Using the T3Client Workspace. For WebLogic JDBC clients, a named Workspace area includes access to any cached JDBC connections to the database (the connectionID), as well as the values set for hard, soft, and idle disconnects. A T3Client can also save arbitrary objects, identified by a String key, into its Workspace for later retrieval. One way to create a revisitable Workspace is by naming it. You name the Workspace when the T3Client is constructed by providing a String name as an argument to the constructor. For example: t3 = new T3Client("t3://bigbox:7001", "mike");
Another way of creating a reenterable Workspace is by saving the String ID of the T3Client's default Workspace, which can be used to reenter it. The ID of the Workspace is available after the T3Client has connected to the WebLogic Server. Here is an example: t3 = new T3Client("t3://bigbox:7001");
t3.connect();
String wsid = t3.services.workspace().getWorkspace().getID();
You can then use the Workspace ID (or a T3Client's name) to create a new T3Client, as follows: t3.disconnect();
t3 = null;
// Reconnect using the "wsid"
System.out.println("Reconnecting client " + wsid);
t3 = new T3Client("t3://bigbox:7001", wsid);
t3.connect();
If you supply a string that does not match any Workspace IDs or T3Client names currently known to the WebLogic Server, it will assume that you want to create a new Workspace and will name it with the supplied string. When you have completed work with the WebLogic Server, you should dispose of the client's resources by calling the disconnect() method in a finally block (covered in the Final Step below). You can set several disconnect timeouts for a T3Client, after you have a T3Client object. WebLogic supports timeouts for hard disconnects (where the socket between the WebLogic Server and its client goes away) and soft disconnects (where the T3Client requests a disconnect by calling its disconnect() method). You can set timeouts for these (in minutes) to delay cleanup of the T3Client object in the WebLogic Server, as follows: t3.setSoftDisconnectTimeoutMins(5);The default for both hard and soft disconnects is an immediate cleanup of the T3Client resources in the WebLogic Server. You can also set these values to T3Client.DISCONNECT_TIMEOUT_NEVER to set the timeout to unlimited. Setting the disconnect timeout determines how long the WebLogic Server will wait after a particular type of disconnect to clean up (destroy) a T3Client's resources -- specifically, its Workspace. Setting a T3Client's soft disconnect timeout to DISCONNECT_TIMEOUT_NEVER essentially extends the lifetime of the T3Client for as long as the WebLogic Server runs. There is a code example that includes naming a T3Client and setting its disconnect timeouts in Using a named, cached JDBC Connection.
Step 3. Setting properties for connectingAfter you have established a WebLogic Server session, you can begin the process of connecting to the DBMS through the WebLogic Server. You will use JDBC Properties objects for setting connection parameters. The Properties objects contain all the information necessary for making a JDBC Connection. A set of Connections can be cached inside a T3Client's Workspace for that T3Client's use, and the T3Client can request one of its cached connections when it executes the getConnection() method with a connection ID. Connection IDs are created very simply: by setting a Property. If the connection ID exists, then it is used; otherwise, a new connection ID is created, and with it is saved all of the other Property information for the JDBC Connection. When you used the cached Connection again, all you will need is the connection ID; the Properties objects are ignored if a connection ID exists. Properties contain the details about how a WebLogic JDBC client should access both the database and the WebLogic Server. After a Properties object is constructed, you can set any number of properties with the put() method, by supplying two arguments: the name of the property and its String value. The properties that we set here in the examples are used by the WebLogic JDBC drivers. You may include any other properties that your particular JDBC driver requires. We use two Properties objects. The first, dbprops in the example below, set parameters for the connection between the WebLogic Server and the DBMS, which you can think of as the two-tier connection. The second Properties object, t3props in the example below, sets parameters for the connection between the WebLogic JDBC Client and the DBMS, with the WebLogic Server between them; we also refer to this as the multitier connection. The WebLogic Server-DBMS Properties object (dbprops) will itself be set as a property of the WebLogic JDBCClient-WebLogic Server-DBMS Properties object (t3props), which will then be used as an argument for the JDBC Connection constructor. We use a java.util.Properties object to set parameters for the connection between the WebLogic Server and the DBMS (the two-tier connection) and the connection between the WebLogic JDBCClient and the DBMS, with the WebLogic Server between them (the multitier connection). The Properties object is then used as an argument for the getConnection() method. For clarity, we have divided the list of Properties into those that apply to the two-tier connection and those that apply to the multitier connection. Properties to be set for the two-tier connection
Properties to be set for the multitier connection
There is one additional property listed here for reference. It is not likely to be used with most of the other properties here, since this property accesses a JDBC Connection from a connection pool. When you set this property, you do not need to set any other properties, since the other attributes for the connection are set when the connection pool is created. This property is usually used in the absence of other properties. It is:
It is important to understand that you will set parameters for two connections:
In this example, we first set two-tier connection properties to connect to an Oracle database ("mydb") on the database server ("DEMO") with the WebLogic native JDBC driver for Oracle, WebLogic jDriver for Oracle. Properties dbprops = new Properties();
dbprops.put("user", "sa");
dbprops.put("password", "");
dbprops.put("server", "DEMO");
dbprops.put("database", "mydb");
Then we set the multitier properties. Note that one of the multitier
properties is the two-tier Properties object. Also note that we
supply a connection ID as part of the multitier properties; if this
connection ID identifies a Connection (and its set of Properties)
that already exists, then the other properties are ignored, since
they have been saved with the connection ID.
Properties t3props = new Properties();
t3props.put("weblogic.t3", t3);
t3props.put("weblogic.t3.dbprops", dbprops);
t3props.put("weblogic.t3.driverClassName",
"weblogic.jdbc.oci.Driver");
t3props.put("weblogic.t3.driverURL",
"jdbc:weblogic:oracle");
t3props.put("weblogic.t3.connectionID",
dbconnid);
t3props.put("weblogic.t3.cacheRows", "100");
t3props.put("weblogic.t3.name", "CustInfo");
t3props.put("weblogic.t3.description",
"customer info connection");
Note that the formats of the class name of the driver and the URL are
different; the class name uses dot-notation, and the URL uses
separating colons.
Using a URL to set WebLogic JDBC propertiesSome development environments set restrictions on the use of a java.util.Properties object for setting multiple database properties. For example, Powersoft's PowerJ uses the Properties object exclusively for setting the username and password for the DBMS. WebLogic has developed a URL scheme to supply all of the other information needed for a WebLogic JDBC connection. For more information on setting WebLogic JDBC properties for connection with a URL, read the Developers Guide, Using URLs with WebLogic products.Setting up an embedded T3ClientIf you do not need an explicit T3Client object for other purposes in your WebLogic JDBC program, you can use an embedded T3Client. An embedded T3Client is created, connected, and disconnected automatically for you underneath. All you must do is set another property in your java.util.Properties object that supplies the URL of the WebLogic Server.Here is a simple example of using an embedded T3Client; this example uses the weblogic.jdbc.t3.Driver for use with JDK 1.1, which contains all of the java.sql JDBC classes. Note that there is no declaration nor construction of a T3Client object in this example.
Class.forName("weblogic.jdbc.t3.Driver").newInstance();
// Set up properties for connecting to the DBMS
Properties dbprops = new Properties();
dbprops.put("user", "scott");
dbprops.put("password", "tiger");
dbprops.put("server", "DEMO20");
Properties t3props = new Properties();
t3props.put("weblogic.t3.dbprops", dbprops);
// Set the URL of WebLogic to create an embedded T3Client
t3props.put("weblogic.t3.serverURL", "t3://localhost:7001");
t3props.put("weblogic.t3.driverClassName",
"weblogic.jdbc.oci.Driver");
t3props.put("weblogic.t3.driverURL", "jdbc:weblogic:oracle");
t3props.put("weblogic.t3.cacheRows", "10");
Connection conn =
DriverManager.getConnection("jdbc:weblogic:t3", t3props);
Statement stmt = conn.createStatement();
stmt.execute("select * from empdemo");
ResultSet rs = stmt.getResultSet();
while (rs.next()) {
System.out.println(rs.getString("empid") + " - " +
rs.getString("name") + " - " +
rs.getString("dept"));
}
ResultSetMetaData rsmd = rs.getMetaData();
stmt.close();
conn.close();
}
You can also set up an embedded T3Client to use a JDBC Connection from
a WebLogic JDBC connection pool, by setting the property
weblogic.t3.connectionPoolID. If you are using a JDBC
Connection from a connection pool, you will need only the properties
that are required for requesting a connection from the pool, as well
as the property weblogic.t3.serverURL property. For more
information on pools, read Using connection pools.
You can also use an embedded T3Client even if you need to set a username and password for a T3User for T3Client-to-WebLogic security. Here is an example. This sets up access to a connection pool "eng" for which the T3User "development" has been added to the weblogic.properties file, as well as a Permission to "reserve" a connection from this pool, with these properties: weblogic.password.development=3Y(sf40!VmoN weblogic.allow.reserve.weblogic.jdbc.connectionPool.eng=development Here is how you would use a connection from this connection pool with an embedded T3Client: Properties t3props = new Properties();
t3props.put("weblogic.t3.serverURL", "t3://localhost:7001");
t3props.put("weblogic.t3.connectionPoolID", "eng");
t3props.put("weblogic.t3.user", "development");
t3props.put("weblogic.t3.password", "3Y(sf40!VmoN");
Note that all of the other properties for connecting, like the location of the database server, are set by the configuration entry in the weblogic.properties file that creates the connection pool at startup. You can find an example entry for a connection pool (commented-out) in the properties file that is shipped with the distribution.
Step 4. Connecting to the DBMSThe WebLogic JDBC client never connects directly to the database, but connects to the WebLogic Server, which accesses the database on behalf of the T3Client. You must supply JDBC drivers for both the two-tier connection (between the WebLogic Server and the DBMS) and the multitier connection (between the WebLogic JDBC client, the WebLogic Server, and the DBMS). The class name and the URL of the two-tier connection is set with a Properties object, as described above. For the connection between the WebLogic JDBC client, the WebLogic Server, and the DBMS, you will supply the class name and URL for the WebLogic JDBC driver, which manages the multitier connection. The WebLogic JDBC driver class name is supplied by calling the Class.forName().newInstance() method with the class name weblogic.jdbc.t3.Driver. Calling Class.forName().newInstance() properly loads and registers the driver class. You supply the URL jdbc:weblogic:t3 for this driver as an argument to the DriverManager.getConnection() method. In this example, we use the Class.forName().newInstance() method to identify and load the WebLogic JDBC driver. Then we create the JDBC Connection with the URL of the WebLogic JDBC driver and a Properties object: // Class name for the WebLogic JDBC
Class.forName("weblogic.jdbc.t3.Driver").newInstance();
Connection conn =
DriverManager.getConnection("jdbc:weblogic:t3",
t3props);
Once you have established a Connection (that is, constructed a JDBC Connection object), you use WebLogic JDBC methods just as you would any other implementation of JDBC.
Cached connections and connection poolsWebLogic provides ways to supply your T3Clients with reusable JDBC Connections. Logging into a DBMS can be an expensive and time-consuming operation. With a reusable connection, the overhead of connecting to the DBMS is incurred just once, when the connection is created. The WebLogic Server holds the connection open until it is needed again. One type of reusable connection is a named, cached JDBC Connection. Another type is a connection pool. A cached JDBC Connection is created, probably used, and then saved in the T3Client's Workspace for later use. Caching a JDBC Connection saves overhead in having to create a Connection over and over again, but a cached Connection also ties up database resources on a long-term basis. When you cache a JDBC Connection, you save its entire state with it. A pool of JDBC Connections can be created when the WebLogic Server starts up, before there are any requests for JDBC Connections, or dynamically by a T3Client. You can also create a connection pool dynamically using the weblogic.Admin class create_pool command. As T3Clients connect to the WebLogic Server, they can obtain a connection from the pool, and then return it to the pool when finished. Creating a pool of connections is a good way to allocate scarce resources (like database connections) among multiple clients. You can set the pool to grow incrementally when all of the connections have been allocated, up to a maximum number of connections. You can also assign sets of users to named pools. A connection pool saves WebLogic Server and DBMS overhead in creating connections, since the connections are created once, and then reused over and over again. Connection pools and cached connections are different. A cached JDBC Connection is created by a particular T3Client, and the details about that JDBC Connection are stored in that T3Client's Workspace. The cached connection lasts only the lifetime of the T3Client. As soon as the WebLogic Server cleans up the resources for that T3Client, the cached connection is destroyed. Connection pools, on the other hand, are available to any T3Client. The lifetime of a connection from a connection pool is not tied in any way to the lifetime of a T3Client. When a T3Client closes a connection from a connection pool, the connection is returned to the pool and becomes available again for other T3Clients, but the connection itself is not closed.
Following are more details on how to create and use cached JDBC
Connections and connection pools. These are specifically "client-side"
Connections and connection pools. You can also take advantage of
another WebLogic enhancement to JDBC for server-side connection
pools, for use in HTTP servlets
Using a named, cached JDBC ConnectionYou can create and name a JDBC Connection and cache the Connection on the WebLogic Server in the T3Client's Workspace so that you can reuse the same JDBC Connection again and again. A T3Client's cached JDBC Connection will last the lifetime of the T3Client's persistence on the WebLogic Server. You can make this lifetime indefinite -- thus giving the T3Client a permanent preserved Workspace on the WebLogic Server that will last the lifetime of the WebLogic Server -- by setting the T3Client's soft disconnect timeout to DISCONNECT_TIMEOUT_NEVER. Once you have set the soft disconnect timeout to never, disconnecting the T3Client by calling the T3Client.disconnect() method will not cause the WebLogic Server to reclaim the T3Client's resources. In this class, we create a named JDBC Connection that we reuse several times. We identify the named JDBC Connection with the java.util.Property connectionID. This class has two methods, a static getConnection() method to create and then reuse the JDBC Connection, and a main(). First, let's examine the code for the getConnection() method in this class. This method returns a JDBC Connection object; if we supply a property "connectionID" that already exists on the WebLogic Server, all of the other properties for login access, etc., are ignored, and the cached JDBC Connection, which contains all the information necessary to resume connection to the database, is used instead. static Connection getConnection(T3Client t3, String dbconnid)
throws Exception
{
// If a connectionID is given, the other properties are used
// only if the connectionID doesn't exist on the WebLogic Server.
// Other values are ignored if the connectionID exists.
Properties dbprops = new Properties();
// Set the two-tier props
dbprops.put("user", "scott");
dbprops.put("password", "tiger");
dbprops.put("server", "DEMO");
Properties t3props = new Properties();
// Set the multitier props, including the connectionID
t3props.put("weblogic.t3", t3);
t3props.put("weblogic.t3.dbprops", dbprops);
t3props.put("weblogic.t3.driverClassName",
"weblogic.jdbc.oci.Driver");
t3props.put("weblogic.t3.driverURL",
"jdbc:weblogic:oracle");
// If dbconnid has been cached, all the preceding properties
// are ignored. The connection is instant
t3props.put("weblogic.t3.connectionID", dbconnid);
Class.forName("weblogic.jdbc.t3.Driver").newInstance();
return DriverManager.getConnection("jdbc:weblogic:t3",
t3props);
}
In the next code example, we carry out the following steps:
T3Client t3 = new T3Client("t3://localhost:7001");
t3.connect();
t3.setSoftDisconnectTimeoutMins(T3Client.DISCONNECT_TIMEOUT_NEVER);
String wsid = t3.services.workspace().getWorkspace().getID();
Then we create a named JDBC Connection to an Oracle database by
calling the getConnection()
method with the name "myconn."
System.out.println("Logging into database and " +
"saving session as myconn");
Connection conn = getConnection(t3, "myconn");
Now we can disconnect the T3Client and set it to null. Since the soft disconnect timeout is never, the WebLogic Server will preserve this client's resources, including its Workspace and its named JDBC Connections. t3.disconnect(); t3 = null;Next we reconnect to the WebLogic Server by creating a new T3Client named with the Workspace ID of the first client. This relinks the T3Client to the Workspace that we created with the first client; in that Workspace is stored the JDBC Connection that we cached under the name "myconn." Then we resume the connection to the Oracle database by calling the getConnection() method with the name "myconn." All of the parameters for connecting already exist. We do some arbitrary database work and then close the JDBC Connection object. t3 = new T3Client("t3://localhost:7001", wsid);
t3.connect();
for (int j = 0; j < 5; j++) {
System.out.println("Reestablishing database connection");
conn = getConnection(t3, "myconn");
System.out.println("Performing query");
QueryDataSet qds = new QueryDataSet(conn, "select * from emp");
qds.fetchRecords();
System.out.println("Record count = " + qds.size());
qds.close();
}
conn.close();
Once you have finished with a T3Client's resources, you can instruct the
WebLogic Server to reclaim those resources by setting the T3Client's soft
disconnect timeout to zero, which effects a cleanup as soon as the
T3Client calls the disconnect() method, as shown here:
t3.setSoftDisconnectTimeoutMins(0);
t3.disconnect();
Using connection poolsAnother method of connecting is by creating a pool of JDBC Connections from which a T3User can request a connection. You can define a connection pool in the weblogic.properties file, called a "startup" connection pool, or you can create a "dynamic" connection pool in a running WebLogic Server from within a T3Client application.Creating a pool of JDBC Connections gives T3Clients ready access to connections that are already open. It removes the overhead of opening a new connection for each DBMS user, since the connections in the pool are shared among the members of the group. Creating a startup connection poolA startup connection pool is declared in the weblogic.properties file. The WebLogic Server opens JDBC connections to the database during the WebLogic startup process and adds the connections to the pool. You define a startup connection pool with an entry after the following pattern in your weblogic.properties file. An example is commented out in the properties file that is shipped with the distribution, under the heading "JDBC Connection Pool Management:" weblogic.jdbc.connectionPool.VirtualName=\
url=JDBC driver URL,\
driver=full package name for JDBC driver,\
loginDelaySecs=seconds between each login attempt,\
initialCapacity=initial number of connections in the pool,\
maxCapacity=max number of connections in the pool,\
capacityIncrement=number of connections to add at a time,\
allowShrinking=true to allow shrinking,\
shrinkPeriodMins=interval before shrinking,\
testTable=name of table for connection test,\
refreshTestMinutes=interval for connection test,\
testConnsOnReserve=true to test connection at reserve,\
testConnsOnRelease=true to test connection at release,\
props=DBMS connection properties
weblogic.allow.reserve.weblogic.jdbc.connectionPool.name=\
T3Users who can use this pool
weblogic.allow.reset.weblogic.jdbc.connectionPool.name=\
T3Users who can reset this pool
weblogic.allow.shrink.weblogic.jdbc.connectionPool.name=\
T3Users who can shrink this pool
The information that you supply is shown above in red. Required information is noted. If you do not supply a value that is required, an exception is thrown when you start the WebLogic Server. Here is a short description of the arguments for this property:
This example, taken from the weblogic.properties file that is shipped with the WebLogic distribution, creates a connection pool named "eng," which is accessible to 3 T3Users (Guest, Joe, and Jill). It allocates a minimum of 4 and a maximum of 10 JDBC connections for an Oracle database with a username of "SCOTT," password "tiger," and server name "DEMO." The WebLogic Server sleeps for 1 second between each connection attempt to prevent refused logins from a DBMS that may be under load or on a saturated network. The connection pool shrinks back to 4 connections when connections in the pool are unused for 15 minutes or more. Every 10 minutes, unused connections are tested and refreshed if they have have gone stale. weblogic.jdbc.connectionPool.eng=\
url=jdbc:weblogic:oracle,\
driver=weblogic.jdbc.oci.Driver,\
loginDelaySecs=1,\
initialCapacity=4,\
maxCapacity=10,\
capacityIncrement=2,\
allowShrinking=true,\
shrinkPeriodMins=15,\
refreshTestMinutes=10,\
testTable=dual,\
props=user=SCOTT;password=tiger;server=DEMO
weblogic.allow.reserve.weblogic.jdbc.connectionPool.eng=\
guest,joe,jill
weblogic.allow.reset.weblogic.jdbc.connectionPool.eng=\
joe,jill
weblogic.allow.shrink.weblogic.jdbc.connectionPool.eng=\
joe,jill
Note that if you have a username with a null password, you shouldn't enter an empty string for the password in the connection pool registration; rather you should simply leave it blank. Here is an example taken from the WebLogic Administrators Guide document on properties: weblogic.jdbc.connectionPool.eng=\
url=jdbc:weblogic:oracle,\
driver=weblogic.jdbc.oci.Driver,\
loginDelaySecs=1,\
initialCapacity=4,\
capacityIncrement=2,\
maxCapacity=10,\
props=user=sa;password=;server=demo
weblogic.allow.reserve.weblogic.jdbc.connectionPool.eng=guest,joe,jill
Creating a dynamic connection pool
A JNDI Dynamic pools can be temporarily disabled, which suspends communication with the database server through any connection in the pool. When a disabled pool is enabled, the state of each connection is the same as when the pool was disabled; clients can continue their database operations right where they left off. A property in the weblogic.properties file, weblogic.allow.admin.weblogic.jdbc.connectionPoolcreate, determines who can create dynamic connection pools. If the property is not set, then only the "system" user can create a dynamic connection pool. For example, the following property allows users "joe" and "jane" to create dynamic connection pools: weblogic.allow.admin.weblogic.jdbc.connectionPoolcreate=joe,jane
You can also create ACLs weblogic.allow.admin.dynapool=joe,jane weblogic.allow.reserve.dynapool=everyone You associate an ACL with a dynamic connection pool when you create the connection pool. The ACL and connection pool are not required to have the same name, and more than one connection pool can make use of a single ACL. If you do not specify an ACL, the "system" user is the default administrative user for the pool and any user can use a connection from the pool. To create a dynamic connection pool in a T3 application, you get an initial JNDI context to the WebLogic JNDI provider, and then look up "weblogic.jdbc.common.JdbcServices." This example shows how this is done: Hashtable env = new Hashtable();
env.put(java.naming.factory.initial,
"weblogic.jndi.WLInitialContextFactory");
// URL for the WebLogic Server
env.put(java.naming.provider.url, "t3://localhost:7001");
env.put(java.naming.security.credentials,
new T3User("joe", "joez_secret_wrdz"));
Context ctx = new InitialContext(env);
// Look up weblogic.jdbc.JdbcServices
weblogic.jdbc.common.JdbcServices jdbc =
(weblogic.jdbc.common.JdbcServices)
ctx.lookup("weblogic.jdbc.JdbcServices");
Once you have loaded weblogic.jdbc.JdbcServices, you pass the weblogic.jdbc.common.JdbcServices.createPool() method a Properties object that describes the pool. The Properties object contains the same properties you use to create a connection pool in the weblogic.properties file, except that the "aclName" property is specific to dynamic connection pools. The following example creates a connection pool named "eng2" for the DEMO Oracle database. The connections log into the database as user "SCOTT" with password "tiger." When the pool is created, one database connection is opened. A maximum of ten connections can be created on this pool. The "aclName" property specifies that the connection pool will use the "dynapool" ACL in the weblogic.properties file. weblogic.jdbc.common.Pool pool = null;
try {
// Set properties for the Connection Pool.
// The properties are the same as those used to define a startup
// connection pool in the weblogic.properties file.
Properties poolProps = new Properties();
poolProps.put("poolName", "eng2");
poolProps.put("url", "jdbc:weblogic:oracle");
poolProps.put("driver", "weblogic.jdbc.oci.Driver");
poolProps.put("initialCapacity", "1");
poolProps.put("maxCapacity", "10");
poolProps.put("props", "user=SCOTT;
password=tiger;server=DEMO");
poolProps.put("aclName", "dynapool"); // the ACL to use
// Creation fails if there is an existing pool with the same name.
jdbc.createPool(poolProps);
}
catch (Exception e) {
system.out.Println("Error creating connection pool eng2.");
}
finally { // close the JNDI context
ctx.close();
}
Obtaining a connection from a connection poolUsing a connection from a connection pool is nearly the same as opening a JDBC connection. The JDBC driver class is weblogic.jdbc.t3Client.Driver and the connection URL is "jdbc:weblogic:t3". To identify the connection pool you want to use, you create a java.util.Properties object and set a property called weblogic.t3.connectionPoolID to the name of the connection pool. Using a connection from a connection pool. You use a connection from a connection pool in your client application by creating a java.util.Properties object, and setting a property called weblogic.t3.connectionPoolID to the name of the connection pool you created in the WebLogic Server's weblogic.properties file. In this simple example, we create a T3Client, set up a Properties object, and then open a connection from the connection pool "eng," for which the weblogic.properties file entry is shown above. T3Client t3 = new T3Client("t3://bigbox:7001");
t3.connect();
// Note that we only need to set two properties,
// the T3Client and the connectionPoolID
Properties t3props = new Properties();
t3props.put("weblogic.t3", t3);
t3props.put("weblogic.t3.connectionPoolID", "eng");
Class.forName("weblogic.jdbc.t3.Driver").newInstance();
Connection conn =
DriverManager.getConnection("jdbc:weblogic:t3",
t3props);
// Do any arbitrary database work
QueryDataSet qds = new QueryDataSet(conn, "select * from emp");
qds.fetchRecords();
System.out.println("Record count = " + qds.size());
qds.close();
// Release the connection
conn.close();
// Disconnect the client
t3.disconnect();
}
Note that the JDBC Connection is released by this client and returned
to the pool before the client disconnects. At the time when
the JDBC connection is returned to the connection pool, any outstanding
JDBC transactions are rolled back and closed.
Waiting on a pool connection to become available. If all of the connections in a pool are in use, the client will, by default, wait until a connection becomes available. You can change this behavior for a client in two ways:
To disable the wait, set the weblogic.t3.waitForConnection property to "false" in the Properties object you pass to DriverManager.getConnection(): Properties t3props = new Properties();
t3props.put("weblogic.t3", t3);
t3props.put("weblogic.t3.connectionPoolID", "eng");
t3props.put("weblogic.t3.waitForConnection", "false");
Class.forName("weblogic.jdbc.t3.Driver").newInstance();
Connection conn =
DriverManager.getConnection("jdbc:weblogic:t3",
t3props);
With the wait disabled, the DriverManager.getConnection() call throws an exception immediately if no connection is available. To specify a period of time to wait for a connection to become available, set the weblogic.t3.waitSecondsForConnection property to the number of seconds you want to wait. This example waits for up to 15 seconds: Properties t3props = new Properties();
t3props.put("weblogic.t3", t3);
t3props.put("weblogic.t3.connectionPoolID", "eng");
t3props.put("weblogic.t3.waitSecondsForConnection", "15");
Class.forName("weblogic.jdbc.t3.Driver").newInstance();
Connection conn =
DriverManager.getConnection("jdbc:weblogic:t3",
t3props);
Managing connection poolsThe weblogic.jdbc.common.Pool and weblogic.jdbc.common.JdbcServices interfaces provide methods to manage connection pools and obtain information about them. Methods are provided for:
Retrieving information about a pool
The poolExists() method tests whether a connection pool with a specified name exists in the WebLogic Server. You can use this method to determine whether a dynamic connection pool has already been created or to ensure that you select a unique name for a dynamic connection pool you want to create. The getProperties() method retrieves the properties for a connection pool. Disabling a connection pool
You can temporarily disable a connection pool, preventing any clients from obtaining a connection from the pool. Only the "system" user or users granted "admin" permission by an ACL associated with a connection pool can disable or enable the pool. After you call disableFreezingUsers(), clients that currently have a connection from the pool are suspended. Attempts to communicate with the database server throw an exception. Clients can, however, close their connections while the connection pool is disabled; the connections are then returned to the pool and cannot be reserved by another client until the pool is enabled. Use disableDroppingUsers() to not only disable the connection pool, but to destroy the client's JDBC connection to the pool. Any transaction on the connection is rolled back and the connection is returned to the connection pool. The client's JDBC connection context is no longer valid. When a pool is enabled after it has been disabled with disableFreezingUsers(), the JDBC connection states for each in-use connection are exactly as they were when the connection pool was disabled; clients can continue JDBC operations exactly where they left off. You can also use the disable_pool and enable_pool commands of the weblogic.Admin class to disable and enable a pool. Shrinking a connection poolA connection pool has a set of properties that define the initial and maximum number of connections in the pool (initialCapacity and maxCapacity), and the number of connections added to the pool when all connections are in use (capacityIncrement). When the pool reaches its maximum capacity, the maximum number of connections are opened, and they remain opened unless you shrink the pool. You may want to drop some connections from the connection pool when a peak usage period has ended, freeing up resources on the WebLogic Server and DBMS. Shutting down a connection pool
These methods destroy a connection pool. Connections are closed and removed from the pool and the pool dies when it has no remaining connections. Only the "system" user or users granted "admin" permission by an ACL associated with a connection pool can destroy the pool. The shutdownSoft() method waits for connections to be returned to the pool before closing them. The shutdownHard() method kills all connections immediately. Clients using connections from the pool get exceptions if they attempt to use a connection after shutdownHard() is called. You can also use the destroy_pool command of the weblogic.Admin class to destroy a pool. Resetting a poolYou can configure a connection pool to test its connections either periodically, or every time a connection is reserved or released. Allowing the WebLogic Server to automatically maintain the integrity of pool connections should prevent most DBMS connection problems. In addition, WebLogic provides methods you can call from an application to refresh all connections in the pool or a single connection you have reserved from the pool. The weblogic.jdbc.common.Pool.reset() method closes and reopens all allocated connections in a connection pool. This may be necessary after the DBMS has been restarted, for example. Often when one connection in a connection pool has failed, all of the connections in the pool are bad. To refresh a single connection, use the refresh() method in the weblogic.jdbc.t3.Connection class. When you call this method, you lose any Statements and Resultsets you had on the connection, plus your application incurs the relatively high cost of opening the connection. Therefore, we recommend that you only refresh a single connection when you get an error that implies that the connection has gone bad. You will need to explicitly cast the JDBC Connection as a (weblogic.jdbc.t3.Connection). Other than that, the refresh() method in the Connection class is used in the same way the reset() method is used for a connection pool. First try an execute action on the Connection that is guaranteed to succeed if the Connection itself is viable. Catch the exception and call the refresh() method. Here is an example. Notice that we cast the JDBC Connection as a weblogic.jdbc.t3.Connection in the last line of this example, in order to take advantage of the WebLogic extension to JDBC.
T3Client t3 = new T3Client("t3://localhost:7001");
t3.connect();
Properties t3props = new Properties();
t3props.put("weblogic.t3", t3);
t3props.put("weblogic.t3.connectionPoolID", "eng");
Class.forName("weblogic.jdbc.t3c.Driver").newInstance();
Connection conn =
DriverManager.getConnection("jdbc:weblogic:t3client",
t3props);
try {
Statement stmt = conn.createStatement();
// This SQL is guaranteed to succeed over a good connection
// to an Oracle DBMS
ResultSet rs = stmt.executeQuery("select 1 from dual");
if (rs != null) {
while (rs.next()) {;}
}
rs.close();
stmt.close();
conn.close();
}
catch(SQLException e) {
// We cast the JDBC Connection as a
// weblogic.jdbc.t3.Connection
// and call the refresh() method on it
((weblogic.jdbc.t3.Connection)conn).refresh();
}
Refreshing a single pool connectionYou can refresh a single connection from a connection pool, or reset the entire connection pool, if one or more connections in the pool go stale. For example, if the DBMS is taken down while the WebLogic Server is actively supporting a pool of connections. A connection pool autorefresh feature, introduced with WebLogic Server 4.0, can also be enabled to periodically test and refresh connections. There are only certain instances when resetting a pool is appropriate. You should never use this feature as a routine part of a user program. Usually, what makes resetting a connection pool necessary is that the DBMS has gone down and the connections in the pool are no longer viable. Attempting to reset the pool before you are certain that the DBMS is up and available again will cause an Exception to be thrown. Resetting a pool should always be a special operation that is carried out by a user with administrative privileges. There are several ways to reset connections pools:
$ java weblogic.Admin WebLogicURL RESET_POOL poolName system passwd
Here is an example of resetting a pool using the reset() method.
This simple code example that tests the demo JDBC connection pool "eng," which is a pool of 5 connections to an Oracle DBMS:
String poolID = "eng";
T3Client t3 = new T3Client("t3://localhost:7001");
t3.connect();
Properties t3props = new Properties();
t3props.put("weblogic.t3", t3);
t3props.put("weblogic.t3.connectionPoolID", poolID);
Class.forName("weblogic.jdbc.t3.Driver").newInstance();
Connection conn =
DriverManager.getConnection("jdbc:weblogic:t3client",
t3props);
try {
// If the connection isn't operable, you will get an SQLException if
// you attempt to execute anything over it
Statement stmt = conn.createStatement();
// This SQL is guaranteed to succeed over a good connection
// to an Oracle DBMS
ResultSet rs = stmt.executeQuery("select 1 from dual");
// Do some arbitrary database work
if (rs != null) {
while (rs.next()) {;}
}
rs.close();
stmt.close();
// Release the connection and return it to the pool
conn.close();
}
// If the try block fails, reset the pool. Note that a program
// that calls this method should have administrator privileges.
// You should not try to reset the pool until you are certain
// that the database is available again.
catch(SQLException e) {
t3.services.jdbc().resetPool(poolID);
}
Setting up ACLs for connection pools in the WebLogic Realm
WebLogic controls access to internal resources like JDBC connection pools through ACLs set up in the WebLogic Realm. Entries for ACLs in the WebLogic Realm are listed as properties in the weblogic.properties file. You can set the Permissions "reserve," "reset," and "shrink" for JDBC connections in a connection pool by entering a property in the properties file. Setting a Permission for the ACL "weblogic.jdbc.connectionPool" limits access to all connection pools. Add Permissions for other users by adding an entry for the ACL name "weblogic.jdbc.connectionPool.poolID," which controls access to the connection pool poolID. The special user system always has Permissions "reserve," "reset," and "shrink" for every ACL, no matter what other Permissions have been set. Example: For backwards compatibility, you can also use the old-style property syntax to grant permission for "reserve" by setting a userlist for the property weblogic.jdbc.connectionPool.poolID=allow=. It is recommended that you upgrade your properties file as soon as possible to reflect the new usage, since WebLogic cannot guarantee how long it will support old-style properties. Inserting, updating, and deleting recordsYou use a JDBC Statement or one of its subclasses, created in the context of the JDBC Connection, to execute queries on the database. The results of the query are contained in a JDBC ResultSet. Use the next() and getXXX() methods in the ResultSet class to access rows in the database.In this example, we first insert ten records into the Employee table. We use a PreparedStatement with the JDBC PreparedStatement "?" syntax. We can make updates to the records using the setInt() and setString() methods from the PreparedStatement class. String inssql = "insert into emp (empno, empname) values (?, ?)";
PreparedStatement pstmt = conn.prepareStatement(inssql);
for (int j = 0; j < 10; j++) {
pstmt.setInt(1, i);
pstmt.setString(2, "John Smith");
pstmt.execute();
}
pstmt.close();
After inserting the values, we check what we inserted by executing a query on the database and using the ResultsSet.next() method to examine the results. We close the ResultSet and Statement objects in the reverse order in which they were instantiated. Statement stmt = conn.createStatement();
ResultSet rs = stmt.execute("select empno, empname from emp");
while (rs.next()) {
System.out.println("Value = " + rs.getString("empno"));
System.out.println("Value = " + rs.getString("empname"));
}
rs.close();
stmt.close();
Here we update the records we inserted, using another PreparedStatement. String updsql = "update emp set empname = ? where empno = ?";
PreparedStatement pstmt1 = conn.prepareStatement(updsql);
for (int j = 0; j < 10; j++) {
pstmt1.setInt(2, j);
pstmt1.setString(1, "Person" + j);
pstmt1.executeUpdate();
}
pstmt1.close();
In this example, we delete the records that we inserted. Again, we use a PreparedStatement and the setInt() method to select records for deletion. String delsql = "delete from emp where empno = ?";
PreparedStatement pstmt2 = conn.prepareStatement(delsql);
for (int j = 0; j < 10; j++) {
pstmt2.setInt(1, j);
pstmt2.executeUpdate();
}
pstmt2.close();
Note that we close each Statement and PreparedStatement object when we are finished using it.
Creating and using stored procedures and functionsYou can create, use, and drop stored procedures and functions with WebLogic JDBC. Use CallableStatement objects (subclass of PreparedStatement) with JDBC PreparedStatement "?" syntax to set parameters.In this example, we drop several stored procedures and functions from a database, using a JDBC Statement that we close when we have finished: Statement stmt = conn.createStatement();
try {stmt.execute("drop procedure proc_squareInt");
} catch (SQLException e) {;}
try {stmt.execute("drop procedure func_squareInt");
} catch (SQLException e) {;}
try {stmt.execute("drop procedure proc_getResults");
} catch (SQLException e) {;}
stmt.close();
Use the JDBC Statement class to create a stored procedure or function, and use the JDBC CallableStatement class to execute them. Stored procedure input parameters are mapped to JDBC IN parameters, using the CallableStatement.setXXX() methods like setInt(), and JDBC PreparedStatement "?" syntax. Stored procedure output parameters are mapped to JDBC OUT parameters, using the CallableStatement.registerOutParameter() methods and JDBC PreparedStatement "?" syntax. A parameter may be both IN and OUT, which requires both a setXXX() and a registerOutParameter() call to be done on the same parameter number. For the Sybase DBMS, the JDBC keyword CALL is used instead of the SQL Server keyword EXECUTE. For details, consult your Sybase documentation. Here we create a Sybase stored procedure, using a JDBC Statement, to square an integer. Then we execute the stored procedure using a CallableStatement. We use the registerOutParameter() method to set an output parameter. Statement stmt1 = conn.createStatement();
stmt1.execute("create procedure proc_squareInt " +
"(@field1 int, @field2 int output) as " +
"begin select @field2 = @field1 * @field1 end");
stmt1.close();
CallableStatement cstmt1 =
conn.prepareCall("{call proc_squareInt(?, ?)}");
cstmt1.registerOutParameter(2, Types.INTEGER);
for (int i = 0; i < 10; i++) {
cstmt1.setInt(1, i);
cstmt1.execute();
System.out.println(i + " " + cstmt1.getInt(2));
}
cstmt1.close();
This example code shows how to create a Sybase stored function that returns the square of an integer. We execute the stored function with a CallableStatement, and use registerOutParameter() to register the return value. Statement stmt2 = conn.createStatement();
stmt2.execute("create procedure func_squareInt (@field2 int) as " +
"begin return @field1 * @field1 end");
stmt2.close();
CallableStatement cstmt2 =
conn.prepareCall("{? = call func_squareInt(?)}");
cstmt2.registerOutParameter(1, Types.INTEGER);
for (int i = 0; i < 10; i++) {
cstmt2.setInt(2, i);
cstmt2.execute();
System.out.println(i + " " + cstmt2.getInt(1));
}
cstmt2.close();
This example code shows how to create a Sybase stored procedure that returns the results of a SQL query. We execute the stored procedure with a CallableStatement and put the results into a ResultSet. You must process all ResultSets returned by a stored procedure using the Statement.execute() and Statement.getResultSet() methods before OUT parameters and return status are available. Statement stmt3 = conn.createStatement();
stmt3.executeUpdate("create procedure proc_getResults as " +
"begin select name from sysusers \n" +
"select gid from sysusers end");
stmt3.close();
CallableStatement cstmt3 =
conn.prepareCall("{call proc_getResults()}");
boolean hasResultSet = cstmt3.execute();
while (hasResultSet) {
ResultSet rs = cstmt3.getResultSet();
while (rs.next())
System.out.println("Value: " + rs.getString(1));
rs.close();
hasResultSet = cstmt3.getMoreResults();
}
cstmt3.close();
Here is example code that shows how to create and call an Oracle stored procedure with Statement and CallableStatement objects. The process is similar to the Sybase procedure. Statement stmt1 = conn.createStatement();
stmt1.execute("CREATE OR REPLACE PROCEDURE " +
"proc_squareInt (field1 IN OUT INTEGER, " +
"field2 OUT INTEGER) IS " +
"BEGIN field2 := field1 * field1; " +
"field1 := field1 * field1; " +
"END proc_squareInt");
stmt1.close();
CallableStatement cstmt1 =
conn.prepareCall("BEGIN proc_squareInt(?, ?); END;");
cstmt1.registerOutParameter(2, Types.INTEGER);
for (int k = 0; k < 100; k++) {
cstmt1.setInt(1, k);
cstmt1.execute();
System.out.println(k + " "
+ cstmt1.getInt(1)
+ " " + cstmt1.getInt(2));
}
cstmt1.close();
Finally, here is sample code for creating and using an Oracle stored function with Statement and CallableStatement objects. Statement stmt2 = conn.createStatement();
stmt2.execute("CREATE OR REPLACE FUNCTION " +
"func_squareInt " +
"(field1 IN INTEGER) RETURN INTEGER IS " +
"BEGIN return field1 * field1; " +
"END func_squareInt;");
stmt2.close();
// Use a stored function
CallableStatement cstmt2 =
conn.prepareCall("BEGIN ? := func_squareInt(?); END;");
cstmt2.registerOutParameter(1, Types.INTEGER);
for (int k = 0; k < 100; k++) {
cstmt2.setInt(2, k);
cstmt2.execute();
System.out.println(k + " "
+ cstmt2.getInt(1)
+ " " + cstmt2.getInt(2));
}
cstmt2.close();
Final Step. Closing the Connection and disconnecting the T3ClientAs with all other JDBC objects, you should close() the Connection, even if your login to the database fails; otherwise you risk exceeding the maximum number of logins. You should also disconnect() the WebLogic JDBCClient from the WebLogic Server. Call the close() and disconnect() methods in a try block inside your finally block, and catch the appropriate Exceptions. Calling these methods within a finally block guarantees that they will be executed even if the code in your main try block throws an exception and does not complete. For example: finally {
if (conn != null)
try { conn.close(); } catch (SQLException sqe) {}
if (t3 != null)
try { t3.disconnect();} catch (Exception e) {}
}
When a client disconnects with the disconnect() method, the WebLogic Server will do a dump stack with an EOF exception. You should ignore EOF exceptions that appear in your Netscape server log on disconnect().
Code summarypackage examples.jdbc;
import java.sql.*;
import weblogic.db.jdbc.*;
import weblogic.common.*;
import java.util.Properties;
public class t3client1 {
public static void main(String argv[]) {
T3Client t3 = null;
Connection conn = null;
try {
t3 = new T3Client("t3://bigbox:7001");
t3.connect();
Properties dbprops = new Properties();
dbprops.put("user", "scott");
dbprops.put("password", "tiger");
dbprops.put("server", getParameter("server"));
Properties t3props = new Properties();
t3props.put("weblogic.t3", t3);
t3props.put("weblogic.t3.dbprops", dbprops);
// Note that the formats of the class name of the driver and the
// URL are different; the class name uses dot-notation, and the
// URL uses separating colons.
t3props.put("weblogic.t3.driverClassName",
"weblogic.jdbc.oci.Driver");
t3props.put("weblogic.t3.driverURL",
"jdbc:weblogic:oracle");
t3props.put("weblogic.t3.cacheRows",
getParameter("cacheRows"));
Class.forName("weblogic.jdbc.t3.Driver").newInstance();
conn = DriverManager.getConnection("jdbc:weblogic:t3client",
t3props);
// Insert a series of records
String inssql = "insert into emp (empno, empname) values (?, ?)";
PreparedStatement pstmt = conn.prepareStatement(inssql);
for (int j = 0; j < 10; j++)
pstmt.setInt(1, i);
pstmt.setString(2, "John Smith");
pstmt.execute();
}
pstmt.close();
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("select empno, " +
"empname from emp");
while (rs.next()) {
System.out.println("Value = " + rs.getString("empno"));
System.out.println("Value = " + rs.getString("empname"));
}
rs.close();
stmt.close();
// Update a series of records
String updsql = "update emp set empname = ? where empno = ?";
PreparedStatement pstmt1 = conn.prepareStatement(updsql);
for (j = 0; j < 10; j++) {
pstmt1.setInt(2, j);
pstmt1.setString(1, "Person" + j);
pstmt1.executeUpdate();
}
pstmt1.close();
// Delete a series of records
String delsql = "delete from emp where empno = ?";
PreparedStatement pstmt2 = conn.prepareStatement(delsql);
for (int j = 0; j < 10; j++) {
pstmt2.setInt(1, j);
pstmt2.executeUpdate();
}
pstmt2.close();
// Create a stored procedures
Statement stmt1 = conn.createStatement();
stmt1.execute("CREATE OR REPLACE PROCEDURE " +
"proc_squareInt (field1 IN OUT INTEGER, " +
"field2 OUT INTEGER) IS " +
"BEGIN field2 := field1 * field1; " +
"field1 := field1 * field1; " +
"END proc_squareInt");
stmt1.close();
// Use a stored procedure
CallableStatement cstmt1 =
conn.prepareCall("BEGIN proc_squareInt(?, ?); END;");
cstmt1.registerOutParameter(2, Types.INTEGER);
for (int k = 0; k < 100; k++) {
cstmt1.setInt(1, k);
cstmt1.execute();
System.out.println(k + " "
+ cstmt1.getInt(1)
+ " " + cstmt1.getInt(2));
}
cstmt1.close();
// Create a stored function
Statement stmt2 = conn.createStatement();
stmt2.execute("CREATE OR REPLACE FUNCTION " +
"func_squareInt (field1 IN INTEGER) " +
"RETURN INTEGER IS " +
"BEGIN return field1 * field1; " +
"END func_squareInt;");
stmt2.close();
// Use a stored function
CallableStatement cstmt2 =
conn.prepareCall("BEGIN ? := func_squareInt(?); END;");
cstmt2.registerOutParameter(1, Types.INTEGER);
for (int k = 0; k < 100; k++) {
cstmt2.setInt(2, k);
cstmt2.execute();
System.out.println(k + " "
+ cstmt2.getInt(1)
+ " " + cstmt2.getInt(2));
}
cstmt2.close();
}
finally {
if (conn != null)
try {conn.close();} catch (SQLException sqe) {}
if (t3 != null)
try {t3.disconnect();} catch (Exception e) {}
}
}
}
Other WebLogic JDBC featuresWebLogic provides several features in its WebLogic jDrivers and in WebLogic JDBC to support database-specific strengths. All of the features supported in the two-tier drivers, and other features specific to multitier use, are available in the multitier environment in WebLogic JDBC. Waiting on Oracle resourcesWith release 2.5, WebLogic supports Oracle's oopt() C functionality, which allows a client to wait until resources become available. The Oracle C function sets options in cases where requested resources are not available; for example, whether to wait for locks. This functionality is described in section 4-97 of The OCI Functions for C. The developer can set whether a client will wait for DBMS resources, or will receive an immediate exception. Here is an example, from the example examples/jdbc/oracle/waiton.java: t3 = new T3Client("t3://bigbox:7001");
t3.connect();
java.util.Properties dbprops = new java.util.Properties();
dbprops.put("user", "scott");
dbprops.put("password", "tiger");
dbprops.put("server", "bigbox");
Properties t3props = new Properties();
t3props.put("weblogic.t3", t3);
t3props.put("weblogic.t3.dbprops", dbprops);
t3props.put("weblogic.t3.driverClassName",
"weblogic.jdbc.oci.Driver");
t3props.put("weblogic.t3.driverURL",
"jdbc:weblogic:oracle");
t3props.put("weblogic.t3.cacheRows",
getParameter("cacheRows"));
Class.forName("weblogic.jdbc.t3.Driver").newInstance();
// You must cast the Connection as a weblogic.jdbc.oci.Connection
// to take advantage of this extension.
Connection conn =
(weblogic.jdbc.oci.Connection)
DriverManager.getConnection("jdbc:weblogic:t3", t3props);
// After constructing the Connection object, immediately call
// the waitOnResources method
conn.waitOnResources(true);
Note that use of this method can cause several error return codes while waiting for internal resources that are locked for short durations. To take advantage of this feature, you must first cast your Connection object as a weblogic.jdbc.oci.Connection, and then call the waitOnResources() method. Extended SQLJavaSoft's JDBC specification includes a feature called SQL Extensions, or SQL Escape Syntax. All of the WebLogic jDriver JDBC drivers support Extended SQL. For more information, see the Developers Guide for your driver. For a listing, see WebLogic JDBC Options.Oracle array fetchesWebLogic jDriver for Oracle offers support for Oracle array fetches by setting the two-tier JDBC Connection property, weblogic.oci.cacheRows. If you are using WebLogic jDriver for Oracle, this feature is also supported in WebLogic JDBC.Take advantage of this feature in WebLogic JDBC by setting the two-tier property weblogic.oci.cacheRows. Multibyte character set supportWebLogic jDriver for Oracle also offers internationalization support (AL24UTFFSS/UTF-8), which is extended to WebLogic JDBC if you are using WebLogic jDriver for Oracle with the WebLogic Server. Full documentation on this feature is available in the Developers Guide for WebLogic jDriver for Oracle.About WebLogic JDBC and Oracle NUMBER columnsOracle provides a column type called NUMBER, which can be optionally specified with a precision and a scale, in the forms NUMBER(P) and NUMBER(P,S). Even in the simple unqualified NUMBER form, this column can hold all number types from small integer values to very large floating point numbers, with high precision. WebLogic jDriver for Oracle reliably converts the values in a column to the Java type requested when a WebLogic jDriver for Oracle application asks for a value from such a column. Of course, if a value of 123.456 is asked for with getInt(), the value will be rounded. The method getObject(), however, poses some problems. WebLogic jDriver for Oracle guarantees to return a Java object which will represent any value in a NUMBER column with no loss in precision. This means that a value of 1 can be returned in an Integer, but a value like 123434567890.123456789 can only be returned in a BigDecimal. There is no metadata from Oracle to report the maximum precision of the values in the column, so WebLogic jDriver for Oracle must decide what sort of object to return based on each value. This means that one ResultSet may return multiple Java types from getObject() for a given NUMBER column. A table full of integer values may all be returned as Integer from getObject(), whereas a table of floating point measurements may be returned primarily as Double, with some Integer if any value happens to be something like "123.00". Oracle does not provide any information to distinguish between a NUMBER value of "1" and a NUMBER of "1.0000000000". There is some more reliable behavior with qualified NUMBER columns, that is, those defined with a specific precision. Oracle's metadata provides these parameters to the driver so WebLogic jDriver for Oracle will always return a Java object appropriate for the given precision and scale, regardless of the values in the table.
The multitier driver add another layer of complexity to this issue. By default, WebLogic fetches a configurable number of ResultSet rows of DBMS data before the multitier JDBC application asks for it, which improves performance as perceived by the client. But because WebLogic does not know in advance what form the client will want the data, WebLogic prefetches rows generically, so that the data sent to a client application is of the same type in any one column of a ResultSet. When using prefetch, the getObject() method cannot be used for number types, because the WebLogic jDriver for Oracle in use by the WebLogic Server might return different Java types in a given column. Consequently, WebLogic prefetches all greater-than-integer numerical data in String form, to guarantee that no precision will be lost. This has no effect on data retrieval in a WebLogic JDBC client application if the data is requested with getInt(), getFloat(), getBigDecimal(), etc. because WebLogic JDBC converts the String to the correct type. But for calls to the getObject() method, WebLogic JDBC returns the String it prefetched. If you want getObject() to behave in the same way in your your multitier client application as in a two-tier WebLogic jDriver for Oracle application -- that is, without prefetch, and potentially with mixed data types in the same column -- turn off row caching in WebLogic by setting the Connection property weblogic.t3.cacheRows to zero (0).
IV. Implementing with WebLogic JDBC and the JDBC-ODBC bridgeThis notated example shows how to use WebLogic JDBC to connect to any vendor's database using the JDBC-ODBC bridge as the two-tier driver.Note: Using the JDBC-ODBC bridge to access a Microsoft Access database with Enterprise JavaBeans is not supported.
Step 1. Importing packagesThe same import packages are required for using the JDBC-ODBC bridge with WebLogic JDBC as with any other WebLogic JDBC class. They are:import java.util.*; import java.sql.*; import weblogic.common.*;
Step 2. Creating the T3ClientThe constructor for a WebLogic JDBC client takes one argument, the URL of the WebLogic Server, which includes the port on which it is listening for T3Client requests. The example places all of the initial work of the program in a try block. try {
t3 = new T3Client("t3://bigbox:7001");
t3.connect();
You should call the disconnect() method on the t3Client in
your finally block, even if the
connection fails.
Step 3. ConnectingUse a java.util.Properties object to set parameters for connecting. We use one set of Properties for the WebLogic Server-to-DBMS connection (the two-tier connection), and another set of Properties for connection between the WebLogic JDBC client, the WebLogic Server, and the DBMS (the multitier connection). The two-tier Properties object itself is set as a multitier Property, and then the multitier Properties object is used as an argument for the Connection constructor. (details on setting Properties) Properties dbprops = new Properties();
dbprops.put("user", "scott");
dbprops.put("password", "tiger");
Properties t3props = new Properties();
t3props.put("weblogic.t3", t3);
t3props.put("weblogic.t3.dbprops", dbprops);
t3props.put("weblogic.t3.driverClassName",
"sun.jdbc.odbc.JdbcOdbcDriver");
t3props.put("weblogic.t3.driverURL",
"jdbc:odbc:Oracle_on_SS2");
t3props.put("weblogic.t3.cacheRows", "10");
Class.forName("weblogic.jdbc.t3.Driver").newInstance();
conn = DriverManager.getConnection("jdbc:weblogic:t3client",
t3props);
checkForWarning(conn.getWarnings());
In the last line in this example, we check for vendor-specific warnings after the connection is established. Here is the code for the method checkForWarning. The method takes as an argument a SQLWarning object and displays information about the SQLState, the warning message, and the database vendor's error code. Note that there may be multiple warnings in a single SQLWarning object. private static boolean checkForWarning (SQLWarning warn)
throws SQLException
{
boolean rc = false;
if (warn != null) {
System.out.println ("\n *** Warning ***\n");
rc = true;
while (warn != null) {
System.out.println ("SQLState: " +
warn.getSQLState ());
System.out.println ("Message: " +
warn.getMessage ());
System.out.println ("Vendor: " +
warn.getErrorCode ());
System.out.println ("");
warn = warn.getNextWarning ();
}
}
return rc;
}
Accessing dataUse the getMetaData method (in the Connection class) to retrieve database metadata. In this example, we display a few details about the database based on the metadata retrieved. DatabaseMetaData dma = conn.getMetaData();
System.out.println("Connected to " + dma.getURL());
System.out.println("Driver " + dma.getDriverName());
System.out.println("Version " + dma.getDriverVersion());
System.out.println("");
Use a Statement object to construct and execute a simple SQL
select statement, and then retrieve the data into a ResultSet. Close
the Statement and ResultSet objects when you have finished using them.
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("SELECT * FROM emp");
dispResultSet (rs);
rs.close();
stmt.close();
We display the results of the query with a private method that takes
as its argument a ResultSet. The dispResultSet() method
prints the column headings for the table using ResultSetMetaData and
then displays the contents of the ResultSet in row major order.
private static void dispResultSet (ResultSet rs)
throws SQLException
{
int i;
ResultSetMetaData rsmd = rs.getMetaData ();
int numCols = rsmd.getColumnCount();
for (i=1; i < = numCols; i++) {
if (i > 1) System.out.print(",");
System.out.print(rsmd.getColumnLabel(i));
}
System.out.println("");
boolean more = rs.next ();
while (more) {
for (i=1; i<=numCols; i++) {
if (i > 1) System.out.print(",");
System.out.print(rs.getString(i));
}
System.out.println("");
more = rs.next ();
}
}
The SQLException is most interesting; we display the same information about a SQL error that we when we checked for SQLWarnings after instantiating a Connection. Note that there may be several SQL errors contained in a single SQLException. catch (SQLException ex) {
System.out.println ("\n*** SQLException caught ***\n");
ex.printStackTrace();
while (ex != null) {
System.out.println ("SQLState: " +
ex.getSQLState ());
System.out.println ("Message: " +
ex.getMessage ());
System.out.println ("Vendor: " +
ex.getErrorCode ());
ex = ex.getNextException ();
System.out.println ("");
}
}
For all other exceptions, we merely print out a stack trace for
debugging purposes.
catch (java.lang.Exception ex) {
ex.printStackTrace ();
}
Final Step. Disconnecting and closing objectsAlways close the Connection and disconnect the T3Client in a finally block to ensure proper cleanup. finally {
if (conn != null)
try {conn.close();} catch (Exception e) {;}
if (t3 != null)
try {t3.disconnect();} catch (Exception e) {;}
}
Code summaryHere is a summary of the code discussed in this example.package examples.jdbc.odbc;
import java.util.*;
import java.sql.*;
import weblogic.common.*;
class simpleselect {
public static void main (String args[]) {
String url = "jdbc:odbc:Oracle_on_SS2";
String query = "SELECT * FROM emp";
T3Client t3 = null;
Connection conn = null;
try {
t3 = new T3Client("t3://bigbox:7001");
t3.connect();
Properties dbprops = new Properties();
dbprops.put("user", "scott");
dbprops.put("password", "tiger");
Properties t3props = new Properties();
t3props.put("weblogic.t3", t3);
t3props.put("weblogic.t3.dbprops", dbprops);
t3props.put("weblogic.t3.driverClassName",
"sun.jdbc.odbc.JdbcOdbcDriver");
t3props.put("weblogic.t3.driverURL", url);
t3props.put("weblogic.t3.cacheRows", "10");
Class.forName("weblogic.jdbc.t3.Driver").newInstance();
conn = DriverManager.getConnection("jdbc:weblogic:t3client",
t3props);
checkForWarning(conn.getWarnings());
DatabaseMetaData dma = conn.getMetaData();
System.out.println("Connected to " + dma.getURL());
System.out.println("Driver " + dma.getDriverName());
System.out.println("Version " + dma.getDriverVersion());
System.out.println("");
// Create a Statement object so we can submit
// SQL statements to the driver
Statement stmt = conn.createStatement();
// Submit a query, creating a ResultSet object
ResultSet rs = stmt.executeQuery(query);
// Display all columns and rows from the result set
dispResultSet (rs);
// Close the result set and statement
rs.close();
stmt.close();
}
catch (SQLException ex) {
// Catch SQLExceptions and display specific error information.
System.out.println ("\n*** SQLException caught ***\n");
ex.printStackTrace();
while (ex != null) {
System.out.println ("SQLState: " + ex.getSQLState ());
System.out.println ("Message: " + ex.getMessage ());
System.out.println ("Vendor: " + ex.getErrorCode ());
ex = ex.getNextException ();
System.out.println ("");
}
}
catch (java.lang.Exception ex) {
// For any other exception, just print out the StackTrace
ex.printStackTrace();
}
finally {
if (conn != null)
try {conn.close();} catch (SQLException sqe) {}
if (t3 != null)
try {t3.disconnect();} catch (Exception e) {}
}
}
private static boolean checkForWarning (SQLWarning warn)
throws SQLException
{
boolean rc = false;
// Take an SQLWarning object and display its
// warning messages. Note that there could be
// multiple warnings chained together.
if (warn != null) {
System.out.println ("\n *** Warning ***\n");
rc = true;
while (warn != null) {
System.out.println ("SQLState: " + warn.getSQLState ());
System.out.println ("Message: " + warn.getMessage ());
System.out.println ("Vendor: " + warn.getErrorCode ());
System.out.println ("");
warn = warn.getNextWarning ();
}
}
return rc;
}
private static void dispResultSet (ResultSet rs)
throws SQLException
{
int i;
ResultSetMetaData rsmd = rs.getMetaData();
int numCols = rsmd.getColumnCount();
for (i=1; i<=numCols; i++) {
if (i > 1) System.out.print(",");
System.out.print(rsmd.getColumnLabel(i));
}
System.out.println("");
boolean more = rs.next();
while (more) {
for (i=1; i<=numCols; i++) {
if (i > 1) System.out.print(",");
System.out.print(rs.getString(i));
}
System.out.println("");
more = rs.next();
}
}
}
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