Understanding JDBC Resources in WebLogic Server
Applications lookup a data source on the JNDI tree or in the local application context (
java:comp/env), depending on how you configure and deploy the object, and then request a database connection. When finished with the connection, the application calls
connection.close(), which returns the connection to the connection pool in the data source. For more information about data sources in WebLogic Server, see Configuring JDBC Data Sources.
An Active GridLink (AGL) datasource provides a connection pool that spans one or more nodes in one or more Oracle RAC clusters. It supports dynamic load balancing of connections across the nodes and handles events that indicates nodes that are added and removed from the cluster(s). See Using Active GridLink Data Sources.
A Multi Data Source is an abstraction around a selected list of Generic data sources that provides load balancing or failover processing between the generic data sources associated with the Multi Data Source. Multi Data Sources are bound to the JNDI tree or local application context just like Generic data sources are bound to the JNDI tree. Applications lookup a Multi Data Source on the JNDI tree or in the local application context (
java:comp/env) just like they do for generic data sources, and then request a database connection. The Multi Data Source determines which Generic data source to use to satisfy the request depending on the algorithm selected in the Multi Data Source configuration: load balancing or failover. For more information about multi data sources, see Configuring JDBC Multi Data Sources.
Ownership of Configured JDBC Resources
WebLogic Administrators typically use the WebLogic Server Administration Console or the WebLogic Scripting Tool (WLST) to create and deploy (target) JDBC modules. These JDBC modules are considered system modules. See JDBC System Modules.
Programmers create modules in a development tool that supports creating an XML descriptor file, then package the JDBC modules with an application (for example, an EAR or WAR file) and pass the application to a WebLogic Administrator to deploy. These JDBC modules are considered application modules. See JDBC Application Modules.
Table 2-1 lists the JDBC module types and how they can be configured and modified.
Table 2-1 JDBC Module Types and Configuration and Management Options
|Module Type||Created with||Add/Remove Modules with Administration Console||Modify with JMX (remotely)||Modify with JSR-88 (non-remotely)||Modify with Administration Console|
WebLogic Server Administration Console or WLST
Oracle Enterprise Pack for Eclipse (OEPE), Oracle JDeveloper, another IDE, or an XML editor
Yes—via a deployment plan
Yes—via a deployment plan
Data Source Configuration Files
The standard JDBC application modules are created using the JEE 6 annotations or schema definitions based on
datasourcedefinition. The proprietary JDBC application modules are a WebLogic-specific extension of Java EE modules and can be configured either within a Java EE application or as stand-alone modules.
These documents conform to the
jdbc-data-source.xsd schema (available at
JDBC System Modules
When you create a JDBC resource (data source) using the WebLogic Server 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
JDBC data sources 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
Generic Data Source Modules
Generic 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.
"Generic" is the term used to distinguish a simple data source from a Multi Data Source or AGL data source.
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
Active GridLink Data Source System Modules
AGL data source system modules are included in the domain's
config.xml file as a
JDBCSystemResource element, similar to generic data source system modules. AGL data sources include an
jdbc-oracle-params section that includes
For more information on AGL data sources, see Using Active GridLink Data Sources.
Multi Data Source System Modules
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
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 generic 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 generic 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
Members of a multi data source must be generic data sources; they cannot be multi data sources or AGL data sources.
For multi data sources, see Configuring JDBC Multi Data Sources.
JDBC Application Modules
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.)
Standard Java EE Application Modules
Java EE 6 provides the ability to programmatically define DataSource resources as application modules for a more flexible and portable method of database connectivity. See Using DataSource Resource Definitions in Developing JDBC Applications for Oracle WebLogic Server.
Proprietary JDBC Application Modules
JDBC resources can also be managed as application modules, similar to standard Java EE modules. A proprietary JDBC application module is simply an XML file that conforms to the
jdbc-data-source.xsd schema (available at
http://www.oracle.com/webfolder/technetwork/weblogic/jdbc-data-source/index.html) and represents a 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
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.
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 proprietary JDBC application module can also be deployed as a stand-alone resource using the
weblogic.Deployer utility or the WebLogic Server 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 WebLogic Server 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.
When deploying proprietary JDBC modules as standalone modules, a multi data source needs to have a deployment order that is greater than the deployment orders of its member generic data sources.
For more information about JDBC application modules, see 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.
Including Drivers in EAR/WAR Files
In WebLogic Server 10.3.6 and higher releases, you can include a database driver in the
APP-INF/lib directory of the EAR/WAR file that contains a packaged data source. This allows you to deploy a self-contained EAR/WAR file that has both the data source and driver required for an application.
You do not need to update the
Classpath of the manifest file to include the driver location.
An EAR has its own classloader and it is shared across all of the nested applications so any of them can use it. You can deploy multiple EAR/WAR files, each with a different driver version. However, if there are other versions of the driver in the system
classpath, set PREFER-WEB-INF-CLASSES=
true in the
weblogic.xml file to ensure that the application uses the driver classes that it was packaged with which it was packaged.
When using the Oracle driver embedded in an EAR or WAR with
ojdbc7.jar, there is a known problem related to cleaning up the associated classloader. To resolve this problem, call
oracle.jdbc.OracleDriver.deregisterHack() from the
contextDestroyed() method of a
You can also use the
WEB-INF/lib directory to hold driver JAR files. The following example shows the location of the various directories in WAR and EAR files.
Application (ear) Web module (war) WEB-INF/lib EJB module META-INF APP-INF/lib
However, you cannot have two versions of the same JAR in both DOMAIN_HOME/lib (see Using a Third-Party JAR File in DOMAIN_HOME/lib or the system classpath and
prefer-application-packages set. That is, you should do only one of the following:
DOMAIN_HOME/libor system classpath to get the driver into all applications in the domain, or
Use the driver embedded in the application.
Note:If you do not adhere to this restriction, it is possible (depending on the JAR, the version changes, and the order in which the JARs are referenced) that a ClassCastException will occur in the application.
If the JAR files are present in multiple locations, the following rules apply:
weblogic.xmlis false, the precedence is: system classpath >
weblogic.xmlis true, the classes in
WEB-INF/libwill take precedence over all other locations.
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:
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
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
The scope in the
jdbc-data-source-params element of the schema may only be set to
Application for packaged data sources. The value
Application is not valid for:
System resources in
config/jdbc, including generic, multi-data sources, and AGL data sources.
Stand-alone data sources that are deployed dynamically or statically using the
<app-deployment>element in the
For these data source types, there is no application to scope the data source and no associated module. WebLogic Server does not generate a scope of
Application. This omission was not flagged as an error in releases of prior to WebLogic Server 10.3.6.0 and is displayed in the console with an invalid name similar to
ds0@null@ds0. For WebLogic Server 10.3.6.0 and higher, an
Error message is logged for this configuration error and the system attempts to set the scope to
Global and display the data source name as
ds0. In future releases, this error may be treated as fatal.
JDBC Data Source Type
Data sources (generic, multi data, Active Gridlink, and Universal Connection pool) need a datasource-type set in the descriptor. This functionality was added in WebLogic Server 12.2.1 and is optional for backward compatibility.
Data sources should have a datasource-type set in the descriptor. This functionality was added in WebLogic Server 12.2.1 and is optional for backward compatibility. The valid values are:
GENERIC—Generic data source
MDS—Multi Data Source
AGL—Active GridLink data source
UCP—Universal Connection Pool data source
datasource-type is not set to
UCP, the following validations are performed:
datasource-typeis set to
AGL, it is treated as an Active GridLink data source even if
ONSlist is configured, and the Active GridLink flag is
datasource-typeis not set to
AGL, it is an error even if
FANenabled is true or an
ONSlist is configured or the Active GridLink flag is
If no data source list exists (it does not have Multi Data Source members) and
datasource-typeis set to anything other than
AGL, it is an error.
If the data source list exists (it has Multi Data Source members) and the
datasource-typeis set to anything other than
MDS, it is an error.
JMX and WLST Access for JDBC Resources
You can create JDBC resources using any of the WebLogic Server administration tools. When you create JDBC resources, WebLogic Server creates MBeans (Managed Beans) for each of the resources. You can then access these MBeans using JMX or the WebLogic Scripting Tool (WLST).
See Summary of System Administration Tools and APIsfor a complete list of WebLogic Server administration tools. See Developing Custom Management Utilities Using JMX for Oracle WebLogic Server and Understanding the WebLogic Scripting Tool for information about using JMX and WLST to access MBeans for JBDC resources.
JDBC MBeans for System Resources
This topic describes the JDBC Bean tree structure.
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"
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
JDBCDataSourceRuntimeMBeanscurrently available in the system.
JDBCMultiDataSourceRuntimeMBean—Which represents a JDBC multi data source deployed on a server or cluster.
JDBCDriverRuntimeMBean—Which represents a JDBC driver that the server loaded into memory.
JDBCDataSourceRuntimeMBeans—Which represents a JDBC generic or AGL data source deployed on a server or cluster.
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 Developing Java EE Management Applications 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.
Example 2-1 WLST Script to Create JDBC Resources
#---------------------------------------------------------------------- # Create JDBC Resources #---------------------------------------------------------------------- import sys from java.lang import System print "@@@ Starting the script ..." global props url = sys.argv usr = sys.argv password = sys.argv 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"))) 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.
See Navigating MBeans (WLST Online) in Understanding the 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.
When using WLST offline, the following characters are not valid in names of management objects: period (.), forward slash (/), or backward slash (\). See Syntax for WLST Commands in Understanding the WebLogic Scripting Tool.
Creating High-Availability JDBC Resources
To improve the availability your JDBC resource and load balance communication between resources you can target or deploy a JDBC data source to the members of a cluster using the WebLogic Server Administration Console.
However, connections do not fail over in the event that a cluster member becomes unavailable for any reason. New connections are created as needed on available cluster members. See Deploying Data Sources on Servers and Clusters.
A multi data source can only use generic data sources that are deployed on the same cluster member (in the same JVM).