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Application bindings

Before an application installed on an application server can start, all enterprise bean (EJB) references and resource references defined in the application must be bound to the actual artifacts (enterprise beans or resources) defined in the application server.

When defining bindings, we specify JNDI names for the referenceable and referenced artifacts in an application. The jndiName values specified for artifacts must be qualified lookup names. An example referenceable artifact is an EJB defined in an application. An example referenced artifact is an EJB or a resource reference used by the application.

Binding definitions are stored in the ibm-xxx-bnd.xml or ibm-xxx-bnd.xmi files of an application. v7.0 or later binding definitions support files with the suffix of XML for EJB 3.x and Web 2.5 and later modules. Modules earlier than Java EE 5 continue to use binding definition files with the suffix of XMI as in previous versions of WebSphere Application Server. The xxx can be ejb-jar, web, application or application-client.


Times when bindings can be defined

We can define bindings at the following times:


Required bindings

Before an application can be successfully deployed, bindings must be defined for references to the following artifacts:

Depending on the references in and artifacts used by the application, we might need to define bindings for other references and artifacts.


Application resource conflicts

Before v8 of the product, application-defined resources such as references and environment entries were bound into the component namespace relative to java:comp/env. In v8.0 and later, an application developer can assign a name to a resource that is a java: URL prefixed with java:module, java:app, or java:global. Each of these URLs resolves to distinct namespaces, different from the component namespace. A java:module namespace is shared among all components in a module, a java:app namespace is shared among all modules in an application, and a java:global namespace is shared among all applications in a cell. Because the namespaces are shared, different resources might be assigned the same name, resulting in conflicts.

Conflicts at the module scope can occur only if two components in the module define resources with the same name. Because of the small size of this scope, it is unlikely for a module to have true conflicts. However, if multiple instances of the same resource definition exist, they must be configured the same. For example, two EJB references to a particular EJB type which are both assigned the same java:module name must both be configured with the same binding data. Otherwise, the two resources will conflict and the application configuration action will fail.

Application-scoped resources are like module-scoped resources. The only difference is that the definitions can originate from any module in the application. As with module-scoped resources, all application-scoped resources that have the same name must be the same type of resource and must be configured with the same binding data.

Global-scoped resources differ from application- and module-scoped resources in that conflicts can occur among different applications. When a conflict occurs, conflicting applications cannot coexist if the resources are not logically the same. If multiple occurrences of a global-scoped resource all identify logically the same resource, they must all be configured with the same binding data in order to not be detected by the product as conflicting. To edit a global-scoped resource for which occurrences for multiple applications exist, all defining applications must be edited in the same session so as not to introduce a conflict. Failure to do so will result in a failure when the session is saved.


Related:

  • Development and assembly tools
  • Naming
  • Configured name bindings
  • EJB 3.0 and EJB 3.1 application bindings overview
  • References in application deployment descriptor files
  • Data source lookups for enterprise beans and web modules
  • Data sources
  • Java EE connector security
  • Message-driven beans - listener port components
  • Assemble applications
  • Configure enterprise application files
  • Developing enterprise beans
  • Install enterprise application files with the console
  • Deploy and administering enterprise applications
  • Developing applications that use JNDI
  • Developing a Java EE client application
  • Developing data access applications
  • Enable J2EE applications to use mail resources with JavaMail
  • Use URL resources within an application
  • Choose a messaging provider
  • Lookup names support in deployment descriptors and thin clients
  • Enterprise application settings
  • EJB JNDI names for beans
  • Map data sources for all 2.x CMP beans settings
  • Map data sources for all 2.x CMP beans
  • EJB references
  • Resource references