@Resource Overview

This example demonstrates the use of the injection of environment entries using @Resource annotation.

The EJB 3.0 specification (EJB Core Contracts and Requirements) section 16.2.2 reads:

A field or method of a bean class may be annotated to request that an entry from the bean's environment be injected. Any of the types of resources or other environment entries described in this chapter may be injected. Injection may also be requested using entries in the deployment descriptor corresponding to each of these resource types.

Environment entries may also be injected into the bean through bean methods that follow the naming conventions for JavaBeans properties. The annotation is applied to the set method for the property, which is the method that is called to inject the environment entry. The JavaBeans property name (not the method name) is used as the default JNDI name.

The PurchaseOrderBean class shows use of field-level @Resource annotation.

The InvoiceBean class shows the use of method-level @Resource annotation.

The source for this example can be checked out from svn:

$ svn co http://svn.apache.org/repos/asf/tomee/tomee/trunk/examples/injection-of-env-entry

To run it change your working directory to the directory injection-of-env-entry and run the following maven2 commands:

$ cd injection-of-env-entry

$ mvn clean install

The Code

Injection through field (field-level injection)

The maxLineItem field in PurchaseOrderBean class is annotated with @Resource annotation to inform the EJB container the location where in the code the injection of a simple environment entry should take place. The default value of 10 is assigned. You can modify the value of the environment entries at deployment time using deployment descriptor (ejb-jar.xml).

@Resource annotation of a field

int maxLineItems = 10;

Injection through a setter method (method-level injection)

The setMaxLineItem method in InvoiceBean class is annotated with @Resource annotation to inject the simple environment entry. Only setters can be used as a way to inject environment entry values.

You could look up the env-entry using JNDI lookup() method and the following name:


The pattern is to combine the fully-qualified class name and the name of a instance field (or a name of the setter method without set prefix and the first letter lowercased).

@Resource annotation of a setter method

public void setMaxLineItems(int maxLineItems) {
    this.maxLineItems = maxLineItems;

Using env-entry in ejb-jar.xml

    <description>The maximum number of line items per invoice.</description>        

Using @Resource annotated env-entry

public void addLineItem(LineItem item) throws TooManyItemsException {
   if (item == null) {
      throw new IllegalArgumentException("Line item must not be null");

   if (itemCount <= maxLineItems) {
   } else {
      throw new TooManyItemsException("Number of items exceeded the maximum limit");

JUnit Test

Writing an JUnit test for this example is quite simple. We need just to write a setup method to create and initialize the InitialContext, and then write our test methods.

Test fixture

protected void setUp() throws Exception {
    Properties properties = new Properties();
    properties.setProperty(Context.INITIAL_CONTEXT_FACTORY, "org.apache.openejb.client.LocalInitialContextFactory");
    properties.setProperty("openejb.deployments.classpath.include", ".*resource-injection.*");
    initialContext = new InitialContext(properties);

Test methods

public void testAddLineItem() throws Exception {
    Invoice order = (Invoice)initialContext.lookup("InvoiceBeanBusinessRemote");
    LineItem item = new LineItem("ABC-1", "Test Item");

    try {
    } catch (TooManyItemsException tmie) {
    fail("Test failed due to: " + tmie.getMessage());


Running the example is fairly simple. Just execute the following commands:

$ cd injection-of-env-entry

$ mvn clean test

 T E S T S
Running org.superbiz.injection.PurchaseOrderBeanTest
Apache OpenEJB 3.0.0-SNAPSHOT    build: 20071218-01:41
INFO - openejb.home = c:\oss\openejb3\examples\injection-of-env-entry
INFO - openejb.base = c:\oss\openejb3\examples\injection-of-env-entry
WARN - Cannot find the configuration file [conf/openejb.xml].  Will attempt to create one for the beans deployed.
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: c:\oss\openejb3\examples\injection-of-env-entry\target\classes
INFO - Configuring app: c:\oss\openejb3\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: c:\oss\openejb3\examples\injection-of-env-entry\target\classes
INFO - Assembling app: c:\oss\openejb3\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=c:\oss\openejb3\examples\injection-of-env-entry\target\classes)
INFO - OpenEJB ready.
OpenEJB ready.
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 2.859 sec
Running org.superbiz.injection.InvoiceBeanTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.031 sec

Results :

Tests run: 4, Failures: 0, Errors: 0, Skipped: 0