docs/resource-injection.adoc

:index-group: Unrevised
:jbake-date: 2018-12-05
:jbake-type: page
:jbake-status: published


= @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

[source,java]
----
@Resource
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:

[source,properties]
----
java:comp/env/org.apache.openejb.examples.resource.InvoiceBean/maxLineItems
----

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

[source,java]
----
@Resource
public void setMaxLineItems(int maxLineItems) {
    this.maxLineItems = maxLineItems;
}
----

=== Using env-entry in ejb-jar.xml

[source,xml]
----
<env-entry>
    <description>The maximum number of line items per invoice.</description>        
    <env-entry-name>org.apache.openejb.examples.injection.InvoiceBean/maxLineItems</env-entry-name>
    <env-entry-type>java.lang.Integer</env-entry-type>
    <env-entry-value>15</env-entry-value>
</env-entry>
----

=== Using @Resource annotated env-entry

[source,java]
----
public void addLineItem(LineItem item) throws TooManyItemsException {
   if (item == null) {
      throw new IllegalArgumentException("Line item must not be null");
   }

   if (itemCount <= maxLineItems) {
      items.add(item);
      itemCount++;
   } 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

[source,java]
----
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

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

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

= Running

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

___________________________
$ cd injection-of-env-entry

$ mvn clean test
___________________________

[source,java]
----
-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running org.superbiz.injection.PurchaseOrderBeanTest
Apache OpenEJB 3.0.0-SNAPSHOT    build: 20071218-01:41
http://tomee.apache.org/
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
----