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Gavin King committed Nov 10, 2009
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43 changes: 41 additions & 2 deletions reference/en-US/ee.xml
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Expand Up @@ -6,14 +6,48 @@
<para>
CDI is fully integrated into the Java EE environment. Beans have access to Java EE resources and JPA persistence
contexts. They may be used in Unified EL expressions in JSF and JSP pages. They may even be injected into other
platform components, such as Servlets and Message-Driven Beans, which are not beans themselves.
platform components, such as servlets and message-driven Beans, which are not beans themselves.
</para>

<section>
<title>Built-in beans</title>

<para>
In the Java EE environment, the container provides the following built-in beans, all with the qualifier
<literal>@Default</literal>:
</para>

<itemizedlist>
<listitem>
<para>
the current JTA <literal>UserTransaction</literal>,
</para>
</listitem>
<listitem>
<para>
a <literal>Principal</literal> representing the current caller identity,
</para>
</listitem>
<listitem>
<para>
the default <ulink src="http://jcp.org/en/jsr/detail?id=303">Bean Validation</ulink>
<literal>ValidationFactory</literal>, and
</para>
</listitem>
<listitem>
<para>
a <literal>Validator</literal> for the default <literal>ValidationFactory</literal>.
</para>
</listitem>
</itemizedlist>

</section>

<section>
<title>Injecting Java EE resources into a bean</title>

<para>
All managed beans may take advantage of Java EE dependency injection using <literal>@Resource</literal>,
All managed beans may take advantage of Java EE component environment injection using <literal>@Resource</literal>,
<literal>@EJB</literal>, <literal>@PersistenceContext</literal>, <literal>@PeristenceUnit</literal> and
<literal>@WebServiceRef</literal>. We've already seen a couple of examples of this, though we didn't pay
much attention at the time:
Expand All @@ -38,6 +72,11 @@ public class Login implements Serializable {
for all managed beans. The <literal>@PostConstruct</literal> method is called after <emphasis>all</emphasis>
injection has been performed.
</para>

<para>
Of course, we advise that component environment injection be used to define CDI resources, and that typesafe
injection be used in application code.
</para>

</section>

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2 changes: 1 addition & 1 deletion reference/en-US/interceptors.xml
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Expand Up @@ -112,7 +112,7 @@ public class TransactionInterceptor {
<programlisting role="JAVA"><![CDATA[@Transactional @Interceptor
public class TransactionInterceptor {
@Inject UserTransaction transaction;
@Resource UserTransaction transaction;
@AroundInvoke
public Object manageTransaction(InvocationContext ctx) throws Exception { ... }
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115 changes: 2 additions & 113 deletions reference/en-US/intro.xml
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Expand Up @@ -947,119 +947,8 @@ public class RandomNumberGenerator {
<para>
A producer field is really just a shortcut that lets us avoid writing a useless getter method. However,
in addition to convenience, producer fields serve a specific purpose as an adaptor for Java EE component
environment injection.
</para>

</section>

<section>
<title>Java EE resources</title>

<para>
Java EE 5 already introduced some limited support for dependency injection, in the form of component
environment injection. A component environment resource is a Java EE component, for example a JDBC
datasource, JMS queue or topic, JPA persistence context, remote EJB or web service.
</para>

<para>
Naturally, there is now a slight mismatch with the new style of dependency injection in CDI. Most notably,
component environment injection relies on string-based names to qualify ambiguous types, and there is no
real consistency as to the nature of the names (sometimes a JNDI name, sometimes a persistence unit name,
sometimes an EJB link, sometimes a nonportable "mapped name"). Producer fields turned out to be an elegant
adaptor to reduce all this complexity to a common model and get component environment resources to
participate in the CDI system just like any other kind of bean.
</para>

<para>
Fields have a duality in that they can both be the target of Java EE component environment injection and be
declared as a CDI producer field. Therefore, they can define a mapping from a string-based name in the
component environment, to a combination of type and qualifiers used in the world of typesafe injection. We
call a producer field that represents a reference to an object in the Java EE component environment a
<emphasis>resource</emphasis>.
</para>

<programlisting role="JAVA"><![CDATA[@Produces @WebServiceRef(lookup="java:app/service/Catalog")
Catalog catalog;]]></programlisting>

<programlisting role="JAVA"><![CDATA[@Produces @Resource(lookup="java:global/env/jdbc/CustomerDatasource")
@CustomerDatabase Datasource customerDatabase;]]></programlisting>

<programlisting role="JAVA"><![CDATA[@Produces @PersistenceContext(unitName="CustomerDatabase")
@CustomerDatabase EntityManager customerDatabasePersistenceContext;]]></programlisting>

<programlisting role="JAVA"><![CDATA[@Produces @PersistenceUnit(unitName="CustomerDatabase")
@CustomerDatabase EntityManagerFactory customerDatabasePersistenceUnit;]]></programlisting>

<programlisting role="JAVA"><![CDATA[@Produces @EJB(ejbLink="../their.jar#PaymentService")
PaymentService paymentService;]]></programlisting>

<para>
These resources can then be injected in the usual way.
</para>

<programlisting role="JAVA"><![CDATA[@Inject Catalog catalog;]]></programlisting>
<programlisting role="JAVA"><![CDATA[@Inject @CustomerDatabase Datasource customerDatabase;]]></programlisting>
<programlisting role="JAVA"><![CDATA[@Inject @CustomerDatabase EntityManager customerDatabaseEntityManager;]]></programlisting>
<programlisting role="JAVA"><![CDATA[@Inject @CustomerDatabase EntityManagerFactory customerDatabaseEntityManagerFactory;]]></programlisting>
<programlisting role="JAVA"><![CDATA[@Inject PaymentService paymentService;]]></programlisting>

<para>
The bean type and qualifiers of the resource are determined by the producer field declaration.
</para>

<para>
It might seem like a pain to have to write these extra producer field declarations, just to gain an additional
level of indirection. You could just as well use component environment injection directly, right? But remember
that you're going to be using resources like the <literal>EntityManager</literal> in several different beans.
Isn't it nicer and more typesafe to write
</para>

<programlisting>@Inject @CustomerDatabase EntityManager</programlisting>

<para>instead of</para>

<programlisting>@PersistenceContext(unitName="CustomerDatabase") EntityManager</programlisting>

<para>
all over the place?
</para>

</section>

<section>
<title>Built-in beans</title>

<para>
In the Java EE environment, we get some additional goodies. The container provides the following
built-in beans, all with the qualifier <literal>@Default</literal>:
</para>

<itemizedlist>
<listitem>
<para>
the current JTA <literal>UserTransaction</literal>,
</para>
</listitem>
<listitem>
<para>
a <literal>Principal</literal> representing the current caller identity,
</para>
</listitem>
<listitem>
<para>
the default <ulink src="http://jcp.org/en/jsr/detail?id=303">Bean Validation</ulink>
<literal>ValidationFactory</literal>, and
</para>
</listitem>
<listitem>
<para>
a <literal>Validator</literal> for the default <literal>ValidationFactory</literal>.
</para>
</listitem>
</itemizedlist>

<para>
Can't wait to get started? Great! In the next two chapters, we'll start working on some examples.
environment injection, but to learn more about that, you'll have to wait until <xref linkend="resources"/>.
Because we can't wait to get to work on some examples.
</para>

</section>
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1 change: 1 addition & 0 deletions reference/en-US/master.xml
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Expand Up @@ -74,6 +74,7 @@

<xi:include href="stereotypes.xml" xmlns:xi="http://www.w3.org/2001/XInclude" />
<xi:include href="specialization.xml" xmlns:xi="http://www.w3.org/2001/XInclude" />
<xi:include href="resources.xml" xmlns:xi="http://www.w3.org/2001/XInclude" />

</part>

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2 changes: 1 addition & 1 deletion reference/en-US/part3.xml
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Expand Up @@ -3,7 +3,7 @@
<partintro>

<para>
The second major theme of Weld is <emphasis>strong typing</emphasis>. The information about the dependencies,
The second major theme of CDI is <emphasis>strong typing</emphasis>. The information about the dependencies,
interceptors and decorators of a bean, and the information about event consumers for an event producer, is
contained in typesafe Java constructs that may be validated by the compiler.
</para>
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96 changes: 96 additions & 0 deletions reference/en-US/resources.xml
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@@ -0,0 +1,96 @@
<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN"
"http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd" [ ]>
<chapter id="resources">

<title>Java EE component environment resources</title>

<para>
Java EE 5 already introduced some limited support for dependency injection, in the form of component
environment injection. A component environment resource is a Java EE component, for example a JDBC
datasource, JMS queue or topic, JPA persistence context, remote EJB or web service.
</para>

<para>
Naturally, there is now a slight mismatch with the new style of dependency injection in CDI. Most notably,
component environment injection relies on string-based names to qualify ambiguous types, and there is no
real consistency as to the nature of the names (sometimes a JNDI name, sometimes a persistence unit name,
sometimes an EJB link, sometimes a nonportable "mapped name"). Producer fields turned out to be an elegant
adaptor to reduce all this complexity to a common model and get component environment resources to
participate in the CDI system just like any other kind of bean.
</para>

<para>
Fields have a duality in that they can both be the target of Java EE component environment injection and be
declared as a CDI producer field. Therefore, they can define a mapping from a string-based name in the
component environment, to a combination of type and qualifiers used in the world of typesafe injection. We
call a producer field that represents a reference to an object in the Java EE component environment a
<emphasis>resource</emphasis>.
</para>

<section>
<title>Defining a resource</title>

<para>We declare a resource by annotating a producer field with a component environment injection
annotation: <literal>@Resource</literal>, <literal>@EJB</literal>, <literal>@PersistenceContext</literal>,
<literal>@PersistenceUnit</literal> or <literal>@WebServiceRef</literal>.</para>

<programlisting role="JAVA"><![CDATA[@Produces @WebServiceRef(lookup="java:app/service/Catalog")
Catalog catalog;]]></programlisting>

<programlisting role="JAVA"><![CDATA[@Produces @Resource(lookup="java:global/env/jdbc/CustomerDatasource")
@CustomerDatabase Datasource customerDatabase;]]></programlisting>

<programlisting role="JAVA"><![CDATA[@Produces @PersistenceContext(unitName="CustomerDatabase")
@CustomerDatabase EntityManager customerDatabasePersistenceContext;]]></programlisting>

<programlisting role="JAVA"><![CDATA[@Produces @PersistenceUnit(unitName="CustomerDatabase")
@CustomerDatabase EntityManagerFactory customerDatabasePersistenceUnit;]]></programlisting>

<programlisting role="JAVA"><![CDATA[@Produces @EJB(ejbLink="../their.jar#PaymentService")
PaymentService paymentService;]]></programlisting>

<para>The field may be static (but not final).</para>

<para>It might feel strange to be declaring resources in Java code. Isn't this stuff that might be
deployment-specific? Certainly, and that's why it makes sense to declare your resources in a class
annotation <literal>@Alternative</literal>.</para>

</section>

<section>
<title>Typesafe resource injection</title>

<para>
These resources can now be injected in the usual way.
</para>

<programlisting role="JAVA"><![CDATA[@Inject Catalog catalog;]]></programlisting>
<programlisting role="JAVA"><![CDATA[@Inject @CustomerDatabase Datasource customerDatabase;]]></programlisting>
<programlisting role="JAVA"><![CDATA[@Inject @CustomerDatabase EntityManager customerDatabaseEntityManager;]]></programlisting>
<programlisting role="JAVA"><![CDATA[@Inject @CustomerDatabase EntityManagerFactory customerDatabaseEntityManagerFactory;]]></programlisting>
<programlisting role="JAVA"><![CDATA[@Inject PaymentService paymentService;]]></programlisting>

<para>
The bean type and qualifiers of the resource are determined by the producer field declaration.
</para>

<para>
It might seem like a pain to have to write these extra producer field declarations, just to gain an additional
level of indirection. You could just as well use component environment injection directly, right? But remember
that you're going to be using resources like the <literal>EntityManager</literal> in several different beans.
Isn't it nicer and more typesafe to write
</para>

<programlisting>@Inject @CustomerDatabase EntityManager</programlisting>

<para>instead of</para>

<programlisting>@PersistenceContext(unitName="CustomerDatabase") EntityManager</programlisting>

<para>
all over the place?
</para>

</section>

</chapter>

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