index-group=Unrevised type=page status=published title=Injection Of Ejbs
This example shows how to use the @EJB annotation on a bean class to refer to other beans. This functionality is often referred as dependency injection (see http://www.martinfowler.com/articles/injection.html), and has been recently introduced in Java EE 5. In this particular example, we will create two session stateless beans * a DataStore session bean * a DataReader session bean The DataReader bean uses the DataStore to retrieve some informations, and we will see how we can, inside the DataReader bean, get a reference to the DataStore bean using the @EJB annotation, thus avoiding the use of the JNDI API. ## DataReader package org.superbiz.injection; import javax.ejb.EJB; import javax.ejb.Stateless; /** * This is an EJB 3.1 style pojo stateless session bean * Every stateless session bean implementation must be annotated * using the annotation @Stateless * This EJB has 2 business interfaces: DataReaderRemote, a remote business * interface, and DataReaderLocal, a local business interface * <p/> * The instance variables 'dataStoreRemote' is annotated with the @EJB annotation: * this means that the application server, at runtime, will inject in this instance * variable a reference to the EJB DataStoreRemote * <p/> * The instance variables 'dataStoreLocal' is annotated with the @EJB annotation: * this means that the application server, at runtime, will inject in this instance * variable a reference to the EJB DataStoreLocal */ //START SNIPPET: code @Stateless public class DataReader { @EJB private DataStoreRemote dataStoreRemote; @EJB private DataStoreLocal dataStoreLocal; @EJB private DataStore dataStore; public String readDataFromLocalStore() { return "LOCAL:" + dataStoreLocal.getData(); } public String readDataFromLocalBeanStore() { return "LOCALBEAN:" + dataStore.getData(); } public String readDataFromRemoteStore() { return "REMOTE:" + dataStoreRemote.getData(); } } ## DataStore package org.superbiz.injection; import javax.ejb.LocalBean; import javax.ejb.Stateless; /** * This is an EJB 3 style pojo stateless session bean * Every stateless session bean implementation must be annotated * using the annotation @Stateless * This EJB has 2 business interfaces: DataStoreRemote, a remote business * interface, and DataStoreLocal, a local business interface */ //START SNIPPET: code @Stateless @LocalBean public class DataStore implements DataStoreLocal, DataStoreRemote { public String getData() { return "42"; } } ## DataStoreLocal package org.superbiz.injection; import javax.ejb.Local; /** * This is an EJB 3 local business interface * A local business interface may be annotated with the @Local * annotation, but it's optional. A business interface which is * not annotated with @Local or @Remote is assumed to be Local */ //START SNIPPET: code @Local public interface DataStoreLocal { public String getData(); } ## DataStoreRemote package org.superbiz.injection; import javax.ejb.Remote; /** * This is an EJB 3 remote business interface * A remote business interface must be annotated with the @Remote * annotation */ //START SNIPPET: code @Remote public interface DataStoreRemote { public String getData(); } ## EjbDependencyTest package org.superbiz.injection; import junit.framework.TestCase; import javax.ejb.embeddable.EJBContainer; import javax.naming.Context; /** * A test case for DataReaderImpl ejb, testing both the remote and local interface */ //START SNIPPET: code public class EjbDependencyTest extends TestCase { public void test() throws Exception { final Context context = EJBContainer.createEJBContainer().getContext(); DataReader dataReader = (DataReader) context.lookup("java:global/injection-of-ejbs/DataReader"); assertNotNull(dataReader); assertEquals("LOCAL:42", dataReader.readDataFromLocalStore()); assertEquals("REMOTE:42", dataReader.readDataFromRemoteStore()); assertEquals("LOCALBEAN:42", dataReader.readDataFromLocalBeanStore()); } } # Running ------------------------------------------------------- T E S T S ------------------------------------------------------- Running org.superbiz.injection.EjbDependencyTest Apache OpenEJB 4.0.0-beta-1 build: 20111002-04:06 http://tomee.apache.org/ INFO - openejb.home = /Users/dblevins/examples/injection-of-ejbs INFO - openejb.base = /Users/dblevins/examples/injection-of-ejbs INFO - Using 'javax.ejb.embeddable.EJBContainer=true' INFO - Configuring Service(id=Default Security Service, type=SecurityService, provider-id=Default Security Service) INFO - Configuring Service(id=Default Transaction Manager, type=TransactionManager, provider-id=Default Transaction Manager) INFO - Found EjbModule in classpath: /Users/dblevins/examples/injection-of-ejbs/target/classes INFO - Beginning load: /Users/dblevins/examples/injection-of-ejbs/target/classes INFO - Configuring enterprise application: /Users/dblevins/examples/injection-of-ejbs INFO - Configuring Service(id=Default Stateless Container, type=Container, provider-id=Default Stateless Container) INFO - Auto-creating a container for bean DataReader: Container(type=STATELESS, id=Default Stateless Container) INFO - Configuring Service(id=Default Managed Container, type=Container, provider-id=Default Managed Container) INFO - Auto-creating a container for bean org.superbiz.injection.EjbDependencyTest: Container(type=MANAGED, id=Default Managed Container) INFO - Enterprise application "/Users/dblevins/examples/injection-of-ejbs" loaded. INFO - Assembling app: /Users/dblevins/examples/injection-of-ejbs INFO - Jndi(name="java:global/injection-of-ejbs/DataReader!org.superbiz.injection.DataReader") INFO - Jndi(name="java:global/injection-of-ejbs/DataReader") INFO - Jndi(name="java:global/injection-of-ejbs/DataStore!org.superbiz.injection.DataStore") INFO - Jndi(name="java:global/injection-of-ejbs/DataStore!org.superbiz.injection.DataStoreLocal") INFO - Jndi(name="java:global/injection-of-ejbs/DataStore!org.superbiz.injection.DataStoreRemote") INFO - Jndi(name="java:global/injection-of-ejbs/DataStore") INFO - Jndi(name="java:global/EjbModule355598874/org.superbiz.injection.EjbDependencyTest!org.superbiz.injection.EjbDependencyTest") INFO - Jndi(name="java:global/EjbModule355598874/org.superbiz.injection.EjbDependencyTest") INFO - Created Ejb(deployment-id=DataReader, ejb-name=DataReader, container=Default Stateless Container) INFO - Created Ejb(deployment-id=DataStore, ejb-name=DataStore, container=Default Stateless Container) INFO - Created Ejb(deployment-id=org.superbiz.injection.EjbDependencyTest, ejb-name=org.superbiz.injection.EjbDependencyTest, container=Default Managed Container) INFO - Started Ejb(deployment-id=DataReader, ejb-name=DataReader, container=Default Stateless Container) INFO - Started Ejb(deployment-id=DataStore, ejb-name=DataStore, container=Default Stateless Container) INFO - Started Ejb(deployment-id=org.superbiz.injection.EjbDependencyTest, ejb-name=org.superbiz.injection.EjbDependencyTest, container=Default Managed Container) INFO - Deployed Application(path=/Users/dblevins/examples/injection-of-ejbs) Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 1.225 sec Results : Tests run: 1, Failures: 0, Errors: 0, Skipped: 0