2 Configuring WebLogic JDBC Resources

JDBC System Modules

When you create a JDBC resource (data source or multi data source) using the Administration Console or using the WebLogic Scripting Tool (WLST), WebLogic Server creates a JDBC module in the config/jdbc subdirectory of the domain directory, and adds a reference to the module in the domain's config.xml file. The JDBC module conforms to the jdbc-data-source.xsd schema (available at http://xmlns.oracle.com/weblogic/jdbc-data-source/1.0/jdbc-data-source.xsd).

JDBC resources that you configure this way are considered system modules. System modules are owned by an Administrator, who can delete, modify, or add similar resources at any time. System modules are globally available for targeting to servers and clusters configured in the domain, and therefore are available to all applications deployed on the same targets and to client applications. System modules are also accessible through JMX as JDBCSystemResourceMBeans.

Data source system modules are included in the domain's config.xml file as a JDBCSystemResource element, which includes the name of the JDBC module file and the list of target servers and clusters on which the module is deployed. Figure 2-1 shows an example of a data source listing in a config.xml file and the module that it maps to.

Figure 2-1 Reference from config.xml to a Data Source System Module

Description of "Figure 2-1 Reference from config.xml to a Data Source System Module"

In this illustration, the config.xml file lists the examples-demo data source as a jdbc-system-resource element, which maps to the examples-demo-jdbc.xml module in the domain\config\jdbc folder.

Similarly, multi data source system modules are included in the domain's config.xml file as a jdbc-system-resource element. The multi data source module includes a data-source-list parameter that maps to the data source modules used by the multi data source. The individual data source modules are also included in the config.xml. Figure 2-2 shows the relationship between elements in the config.xml file and the system modules in the config/jdbc directory.

Figure 2-2 Reference from config.xml to Multi Data Source and Data Source System Modules

Description of "Figure 2-2 Reference from config.xml to Multi Data Source and Data Source System Modules"

In this illustration, the config.xml file lists three JDBC modules—one multi data source and the two data sources used by the multi data source, which are also listed within the multi data source module. Your application can look up any of these modules on the JNDI tree and request a database connection. If you look up the multi data source, the multi data source determines which of the other data sources to use to supply the database connection, depending on the data sources in the data-source-list parameter, the order in which the data sources are listed, and the algorithm specified in the algorithm-type parameter. For more information about multi data sources, see Chapter 5, "Configuring JDBC Multi Data Sources."

JDBC Application Modules

JDBC resources can also be managed as application modules, similar to standard Java EE modules. A JDBC application module is simply an XML file that conforms to the jdbc-data-source.xsd schema (available at http://xmlns.oracle.com/weblogic/jdbc-data-source/1.0/jdbc-data-source.xsd) and represents a data source or a multi data source.

JDBC modules can be included as part of an Enterprise Application as a packaged module. Packaged modules are bundled with an EAR or exploded EAR directory, and are referenced in all appropriate deployment descriptors, such as the weblogic-application.xml and ejb-jar.xml deployment descriptors. The JDBC module is deployed along with the enterprise application, and can be configured to be available only to the enclosing application or to all applications. Using packaged modules ensures that an application always has access to required resources and simplifies the process of moving the application into new environments. With packaged JDBC modules, you can migrate your application and the required JDBC configuration from environment to environment, such as from a testing environment to a production environment, without opening an EAR file and without extensive manual data source reconfiguration.

In contrast to system resource modules, JDBC modules that are packaged with an application are owned by the developer who created and packaged the module, rather than the Administrator who deploys the module. This means that the Administrator has more limited control over packaged modules. When deploying a resource module, an Administrator can change resource properties that were specified in the module, but the Administrator cannot add or delete modules. (As with other Java EE modules, deployment configuration changes for a resource module are stored in a deployment plan for the module, leaving the original module untouched.)

By definition, packaged JDBC modules are included in an enterprise application, and therefore are deployed when you deploy the enterprise application. For more information about deploying applications with packaged JDBC modules, see Deploying Applications to Oracle WebLogic Server.

A JDBC application module can also be deployed as a stand-alone resource using the weblogic.Deployer utility or the Administration Console, in which case the resource is typically available to the server or cluster targeted during the deployment process. JDBC resources deployed in this manner are called stand-alone modules and can be reconfigured using the Administration Console or a JSR-88 compliant tool, but are unavailable through JMX or WLST.

Stand-alone JDBC modules promote sharing and portability of JDBC resources. You can create a data source configuration and distribute it to other developers. Stand-alone JDBC modules can also be used to move data source configuration between domains, such as between the development domain and the staging domain.

For more information about JDBC application modules, see Appendix A, "Configuring JDBC Application Modules for Deployment."

For information about deploying stand-alone JDBC modules, see "Deploying JDBC, JMS, WLDF Application Modules" in Deploying Applications to Oracle WebLogic Server."

JDBC Module File Naming Requirements

All WebLogic JDBC module files must end with the -jdbc.xml suffix, such as examples-demo-jdbc.xml. WebLogic Server checks the file name when you deploy the module. If the file does not end in -jdbc.xml, the deployment will fail and the server will not boot.

JDBC Modules in Versioned Applications

When you use production redeployment (versioning) to deploy a version of an application that includes a packaged JDBC module, WebLogic Server identifies the data source defined in the JDBC module with a name in the following format:

application_id#version_id@module_name@data_source_name

This name is used for data source run-time MBeans and for registering the data source instance with the WebLogic Server transaction manager.

If transactions in a retiring version of an application time out and the version of the application is then undeployed, you may have to manually resolve any pending or incomplete transactions on the data source in the retired version of the application. After a data source is undeployed (in this case, with the retired version of the application), the WebLogic Server transaction manager cannot recover pending or incomplete transactions.

For more information about production redeployment, see:

• "Developing Applications for Production Redeployment" in Developing Applications for Oracle WebLogic Server

• "Using Production Redeployment to Update Applications" in Deploying Applications to Oracle WebLogic Server

JDBC Schema

In support of the modular deployment model for JDBC resources in WebLogic Server, Oracle provides a schema for WebLogic JDBC objects: weblogic-jdbc.xsd. When you create JDBC resource modules (descriptors), the modules must conform to the schema. IDEs and other tools can validate JDBC resource modules based on the schema.

The schema is available at http://xmlns.oracle.com/weblogic/jdbc-data-source/1.0/jdbc-data-source.xsd.

JDBC MBeans for System Resources

Figure 2-3 shows the hierarchy of the MBeans for JDBC objects in a WebLogic domain.

Figure 2-3 JDBC Bean Tree

Description of "Figure 2-3 JDBC Bean Tree"

The JDBCSystemResourceMBean is a container for the JavaBeans created from a data source module. However, all JMX access for a JDBC data source is through the JDBCSystemResourceMBean. You cannot directly access the individual JavaBeans created from the data source module.

JDBC Management Objects in the Java EE Management Model (JSR-77 Support)

The WebLogic Server JDBC subsystem supports JSR-77, which defines the Java EE Management Model. The Java EE Management Model is used for monitoring the run-time state of a Java EE Web application server and its resources. You can access the Java EE Management Model to monitor resources, including the WebLogic JDBC subsystem as a whole, JDBC drivers loaded into memory, and JDBC data sources.

To comply with the specification, Oracle added the following run-time MBean types for the WebLogic JDBC subsystem:

• JDBCServiceRuntimeMBean—Which represents the JDBC subsystem and provides methods to access the list of JDBCDriverRuntimeMBeans and JDBCDataSourceRuntimeMBeans currently available in the system.

• JDBCDriverRuntimeMBean—Which represents a JDBC driver that the server loaded into memory.

• JDBCDataSourceRuntimeMBeans—Which represents a JDBC data source deployed on a server or cluster.

  Note:

  WebLogic JDBC run-time MBeans do not implement the optional Statistics Provider interfaces specified by JSR-77.

For more information about using the Java EE management model with WebLogic Server, see Monitoring and Managing With the Java EE Management APIs for Oracle WebLogic Server.

Using WLST to Create JDBC System Resources

Basic tasks you need to perform when creating JDBC resources with the WLST are:

• Start an edit session.

• Create a JDBC system module that includes JDBC system resources, such as pools, data sources, multi data sources, and JDBC drivers.

• Target your JDBC system module.

#----------------------------------------------------------------------
# Create JDBC Resources
#----------------------------------------------------------------------

import sys
from java.lang import System

print "@@@ Starting the script ..."
global props

url = sys.argv[1]
usr = sys.argv[2]
password = sys.argv[3]

connect(usr,password, url)
edit()
startEdit()

servermb=getMBean("Servers/examplesServer")
   if servermb is None:
      print '@@@ No server MBean found'
else:
   def addJDBC(prefix):

   print("")
   print("*** Creating JDBC resources with property prefix " + prefix)

# Create the Connection Pool.  The system resource will have
# generated name of <PoolName>+"-jdbc"

   myResourceName = props.getProperty(prefix+"PoolName")
   print("Here is the Resource Name: " + myResourceName)

   jdbcSystemResource = wl.create(myResourceName,"JDBCSystemResource")
   myFile = jdbcSystemResource.getDescriptorFileName()
   print ("HERE IS THE JDBC FILE NAME: " + myFile)

   jdbcResource = jdbcSystemResource.getJDBCResource()
   jdbcResource.setName(props.getProperty(prefix+"PoolName"))

# Create the DataSource Params
   dpBean = jdbcResource.getJDBCDataSourceParams()
   myName=props.getProperty(prefix+"JNDIName")
   dpBean.setJNDINames([myName])

# Create the Driver Params
   drBean = jdbcResource.getJDBCDriverParams()
   drBean.setPassword(props.getProperty(prefix+"Password"))
   drBean.setUrl(props.getProperty(prefix+"URLName"))
   drBean.setDriverName(props.getProperty(prefix+"DriverName"))

   propBean = drBean.getProperties()
   driverProps = Properties()
   driverProps.setProperty("user",props.getProperty(prefix+"UserName"))

   e = driverProps.propertyNames()
   while e.hasMoreElements() :
      propName = e.nextElement()
      myBean = propBean.createProperty(propName)
      myBean.setValue(driverProps.getProperty(propName))

# Create the ConnectionPool Params
   ppBean = jdbcResource.getJDBCConnectionPoolParams()
   ppBean.setInitialCapacity(int(props.getProperty(prefix+"InitialCapacity")))
   ppBean.setMaxCapacity(int(props.getProperty(prefix+"MaxCapacity")))
   ppBean.setCapacityIncrement(int(props.getProperty(prefix+"CapacityIncrement")))

   if not props.getProperty(prefix+"ShrinkPeriodMinutes") == None:
      ppBean.setShrinkFrequencySeconds(int(props.getProperty(prefix+"ShrinkPeriodMinutes")))
   if not props.getProperty(prefix+"TestTableName") == None:
      ppBean.setTestTableName(props.getProperty(prefix+"TestTableName"))

   if not props.getProperty(prefix+"LoginDelaySeconds") == None:
      ppBean.setLoginDelaySeconds(int(props.getProperty(prefix+"LoginDelaySeconds")))

# Adding KeepXaConnTillTxComplete to help with in-doubt transactions.
   xaParams = jdbcResource.getJDBCXAParams()
   xaParams.setKeepXaConnTillTxComplete(1)

# Add Target
   jdbcSystemResource.addTarget(wl.getMBean("/Servers/examplesServer"))
.
.
.

How to Modify and Monitor JDBC Resources

You can modify or monitor JDBC objects and attributes by using the appropriate method available from the MBean.

• You can modify JDBC objects and attributes using the set, target, untarget, and delete methods.

• You can monitor JDBC run-time objects using get methods.

For more information, see "Navigating MBeans (WLST Online)" in Oracle WebLogic Scripting Tool.

Best Practices when Using WLST to Configure JDBC Resources

This section provides best practices information when using WLST to configure JDBC resources:

• Trap for Null MBean objects (such as pools, data sources, drivers) before trying to manipulate the MBean object.