Overview
The EJB 3.0 spec added Dependency Injection as a main feature. The @Resource annotation can be used to inject several things including EntityManagers, DataSources, Topics, Queues, etc. Most of these are container supplied objects. It is possible, however, to supply your own values to be injected via an <env-entry> in your ejb-jar.xml deployment descriptor. EJB 3.0 supported env-entry types are limited to the following:
- java.lang.String
- java.lang.Integer
- java.lang.Short
- java.lang.Float
- java.lang.Double
- java.lang.Byte
- java.lang.Character
- java.lang.Boolean
It should be noted that OpenEJB does not restrict you to just these data types and allows for anything convertible from a String to be injected provided there is a java.beans.PropertyEditor installed to handle the type you want. Additionally, a plain properties file packed in your META-INF directory can be used to supply the injected values instead of using the ejb-jar.xml. See the Custom Injection example for details.
The source for this example is the "injection-of-env-entry" directory located in the openejb-examples.zip available on the download page.
The Code
Annotated Bean Class
The use of the @Resource annotation isn't limited to setters. For example, this annotation could have been used on the corresponding field like so:
@Resource private int maxLineItems;
ejb-jar.xml
Test Case
Running it
Running the example is fairly simple. In the "injection-of-env-entry" directory of the examples zip, just run:
$ mvn clean install
Which should create output like the following.
------------------------------------------------------- T E S T S ------------------------------------------------------- Running org.superbiz.injection.PurchaseOrderBeanTest Apache OpenEJB 3.0 build: 20080408-04:13 http://openejb.apache.org/ INFO - openejb.home = /Users/dblevins/work/openejb-3.0/examples/injection-of-env-entry INFO - openejb.base = /Users/dblevins/work/openejb-3.0/examples/injection-of-env-entry 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 - Configuring Service(id=Default JDK 1.3 ProxyFactory, type=ProxyFactory, provider-id=Default JDK 1.3 ProxyFactory) INFO - Found EjbModule in classpath: /Users/dblevins/work/openejb-3.0/examples/injection-of-env-entry/target/classes INFO - Configuring app: /Users/dblevins/work/openejb-3.0/examples/injection-of-env-entry/target/classes INFO - Configuring Service(id=Default Stateful Container, type=Container, provider-id=Default Stateful Container) INFO - Auto-creating a container for bean InvoiceBean: Container(type=STATEFUL, id=Default Stateful Container) INFO - Loaded Module: /Users/dblevins/work/openejb-3.0/examples/injection-of-env-entry/target/classes INFO - Assembling app: /Users/dblevins/work/openejb-3.0/examples/injection-of-env-entry/target/classes INFO - Jndi(name=InvoiceBeanRemote) --> Ejb(deployment-id=InvoiceBean) INFO - Jndi(name=PurchaseOrderBeanRemote) --> Ejb(deployment-id=PurchaseOrderBean) INFO - Created Ejb(deployment-id=InvoiceBean, ejb-name=InvoiceBean, container=Default Stateful Container) INFO - Created Ejb(deployment-id=PurchaseOrderBean, ejb-name=PurchaseOrderBean, container=Default Stateful Container) INFO - Deployed Application(path=/Users/dblevins/work/openejb-3.0/examples/injection-of-env-entry/target/classes) Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 1.331 sec Running org.superbiz.injection.InvoiceBeanTest Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.068 sec Results : Tests run: 4, Failures: 0, Errors: 0, Skipped: 0