Technotrance, Illusions and Perspectives

I am working on an persistence example using PrimeFaces, Google Guice and Hibernate. Following are the four steps to inject a JPA EntityManager into the Manager  (Appfuse parlance) / DAO Layer:

1) Define META-INF/persistence.xml containing JPA Configuration (similar to hibernate.cfg.xml)

<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"
 version="1.0">

 <persistence-unit name="persdb" transaction-type="RESOURCE_LOCAL">
 <provider>org.hibernate.ejb.HibernatePersistence</provider>
 <properties>
 ...
 </properties>
 </persistence-unit>

</persistence>

2) Create a startup controller Guice bean

@Controller(name="startupBean", startup=true)
public class StartupBean
{    public StartupBean()
      {}
}

3) Create a Google Guice Module

public class MyModule implements Module
{       public void configure(Binder binder)
          {   AnnotatedBindingBuilder bindingBuilder = binder.bind(MyDataService.class);
              ScopedBindingBuilder scopedBuilder = bindingBuilder.to(MyDataServiceImpl.class);
              scopedBuilder.in(SINGLETON);
          }
}

and create a context parameter in WEB-INF/web.xml

<context-param>
 <param-name>optimus.CONFIG_MODULES</param-name>
 <param-value>mypackage.MyModule,org.primefaces.optimus.persistence.JPAModule
 </param-value>
 </context-param>

Note: org.primefaces.optimus.persistence.JPAModule actually injects the EntityManager reading the META-INF/persistence.xml

4) Create the DaraService implementation containing the injected EntityManager

public class MyDataServiceImpl implements MyDataService
{        @Inject
            private EntityManager em;
           //all methods using JPA entityManager here

}

No other configuration xmls to be changed. Ain’t it cool!