{"id":516,"date":"2011-08-12T20:36:00","date_gmt":"2011-08-12T17:36:00","guid":{"rendered":"http:\/\/www.javacodegeeks.com\/2012\/10\/basic-ejb-references-injection-and-lookup.html"},"modified":"2012-11-01T22:25:07","modified_gmt":"2012-11-01T20:25:07","slug":"basic-ejb-references-injection-and","status":"publish","type":"post","link":"https:\/\/www.javacodegeeks.com\/2011\/08\/basic-ejb-references-injection-and.html","title":{"rendered":"Basic EJB References, Injection and Lookup"},"content":{"rendered":"
In the first part<\/a> of this series we’ve introduced the mechanisms provided by the Enterprise JavaBeans v. 3.0 Specification<\/a> to define EJB components, declare a reference to an EJB and wiring them up both by dependency injection or programmatic JNDI lookup.<\/p>\n

In this blog post we’ll examine some basic examples to understand how to use the EJB API.<\/p>\n

A Basic EJB<\/span><\/strong><\/p>\n

An EJB is basically a POJO with some extra EJB metadata. The required metadata to deploy it as an EJB component can be provided both by using the EJB annotations or by the standard deployment descriptor. The following class implements a very basic stateless session EJB:<\/p>\n

package es.reacts;\r\n\r\nimport javax.ejb.Stateless;\r\n\r\n@Stateless(name = \"UniqueLocalSessionEJB\")\r\npublic class UniqueLocalSessionEJBBean implements UniqueLocalBusinessInterface {\r\n   public UniqueLocalSessionEJBBean() {\r\n   }\r\n\r\n   public String sayLocalHello() {\r\n    return this.getClass().getName() + \"::\" + \"Local hello.\";\r\n   }\r\n}<\/pre>\n
As you may recollect from our previous blog post, the @Stateless<\/i> annotation is used to define a stateless<\/i> session bean. The optional name<\/i> element is used to define the session bean name<\/i>. This element is analogous to the <ejb-name\/> element of the standard deployment descriptor. This element defaults to the unqualified<\/i> name of the bean class (UniqueLocalSessionEJBBean<\/i> in the example above), and the example above uses it to rename the bean to UniqueLocalSessionEJB<\/i>.<\/p>\n
Since we’re using the @Stateless<\/i> annotation, there’s no further need to declare the EJB in the deployment descriptor.<\/p>\n
In this example, we’re assuming that the EJB is packaged in an EJB module that depends on the module containing the definition of its business interface (as explained in the following section.)<\/p>\n
Business interfaces<\/strong><\/p>\n
Every EJB implements one or more business interfaces. Business interfaces can be local<\/i> or remote<\/i>. The most important differences between the two types of business interfaces can be summarized as follows:<\/p>\n