The Java EE 7 Tutorial
35.2 Developing Embeddable Enterprise Bean Applications
All embeddable enterprise bean containers support the features listed in Table 35-1.
Table 35-1 Required Enterprise Bean Features in the Embeddable Container
|Enterprise Bean Feature||Description|
Local session beans
Local and no-interface view stateless, stateful, and singleton session beans. All method access is synchronous. Session beans must not be web service endpoints.
Container-managed and bean-managed transactions.
Declarative and programmatic security.
Class-level and method-level interceptors for session beans.
Container providers are allowed to support the full set of features in enterprise beans, but applications that use the embedded container will not be portable if they use enterprise bean features not listed in Table 35-1, such as the timer service, session beans as web service endpoints, or remote business interfaces.
The embedded container, the enterprise bean components, and the client all are executed in the same virtual machine using the same classpath. As a result, developers can run an application that uses the embedded container just like a typical Java SE application, as follows:
java -classpath mySessionBean.jar:containerProviderRuntime.jar:myClient.jar \ com.example.ejb.client.Main
In the above example,
mySessionBean.jar is an EJB JAR containing a local stateless session bean,
containerProviderRuntime.jar is a JAR file supplied by the enterprise bean provider that contains the needed runtime classes for the embedded container, and
myClient.jar is a JAR file containing a Java SE application that calls the business methods in the session bean through the embedded container.
In GlassFish Server, the runtime JAR that includes the classes for the embedded container is
javax.ejb.embedded.EJBContainer abstract class represents an instance of the enterprise bean container and includes factory methods for creating a container instance. The
EJBContainer.createEJBContainer method is used to create and initialize an embedded container instance.
The following code snippet shows how to create an embedded container that is initialized with the container provider's default settings:
EJBContainer ec = EJBContainer.createEJBContainer();
By default, the embedded container will search the virtual machine classpath for enterprise bean modules: directories containing a
META-INF/ejb-jar.xml deployment descriptor, directories containing a class file with one of the enterprise bean component annotations (such as
@Stateless), or JAR files containing an
ejb-jar.xml deployment descriptor or class file with an enterprise bean annotation. Any matching entries are considered enterprise bean modules within the same application. Once all the valid enterprise bean modules have been found in the classpath, the container will begin initializing the modules. When the
createEJBContainer method successfully returns, the client application can obtain references to the client view of any enterprise bean module found by the embedded container.
An alternate version of the
EJBContainer.createEJBContainer method takes a
Map of properties and settings for customizing the embeddable container instance:
Properties props = new Properties(); props.setProperty(...); ... EJBContainer ec = EJBContainer.createEJBContainer(props);
Developers can specify exactly which enterprise bean modules the embedded container will initialize. To explicitly specify the enterprise bean modules initialized by the embedded container, set the
The modules may be located either in the virtual machine classpath in which the embedded container and client code run, or alternately outside the virtual machine classpath.
To specify modules in the virtual machine classpath, set
EJBContainer.MODULES to a
String to specify a single module name, or a
String array containing the module names. The embedded container searches the virtual machine classpath for enterprise bean modules matching the specified names:
Properties props = new Properties(); props.setProperty(EJBContainer.MODULES, "mySessionBean"); EJBContainer ec = EJBContainer.createEJBContainer(props);
To specify enterprise bean modules outside the virtual machine classpath, set
EJBContainer.MODULES to a
java.io.File object or an array of
File objects. Each
File object refers to an EJB JAR file, or a directory containing an expanded EJB JAR file:
Properties props = new Properties(); File ejbJarFile = new File(...); props.setProperty(EJBContainer.MODULES, ejbJarFile); EJBContainer ec = EJBContainer.createEJBContainer(props);
To look up session bean references in an application using the embedded container, use an instance of
EJBContainer to retrieve a
javax.naming.Context object. Call the
EJBContainer.getContext method to retrieve the
EJBContainer ec = EJBContainer.createEJBContainer(); Context ctx = ec.getContext();
References to session beans can then be obtained using the portable JNDI syntax detailed in Portable JNDI Syntax. For example, to obtain a reference to
MySessionBean, a local session bean with a no-interface view, use the following code:
MySessionBean msb = (MySessionBean) ctx.lookup("java:global/mySessionBean/MySessionBean");
From the client, call the
close method of the instance of
EJBContainer to shut down the embedded container:
EJBContainer ec = EJBContainer.createEJBContainer(); ... ec.close();
While clients are not required to shut down
EJBContainer instances, doing so frees resources consumed by the embedded container. This is particularly important when the virtual machine under which the client application is running has a longer lifetime than the client application.