Network Deployment (Distributed operating systems), v8.0 > End-to-end paths > Web services - RESTful services
Using Java contexts and dependency injection with JAX-RS
Java API for RESTful Web Services (JAX-RS) root resources and providers can be used in a Java Contexts and Dependency Injection (JCDI) enabled WAR. Simply add a valid WEB-INF/beans.xml file to your WAR file and any JAX-RS root resources and providers that are valid JCDI beans can use JCDI functionality. JAX-WSJAX-RS classes in a JCDI-enabled archive can have @javax.inject.Inject annotated injection points, participate in JCDI lifecycle scopes, raise JCDI events, and have method interceptors and decorators.
JAX-RS root resource and provider classes must have a valid JCDI managed bean constructor. In general, if your classes have a constructor that has a parameter annotated with the @javax.ws.rs.core.Context annotation or with any JAX-RS parameter annotation such as @javax.ws.rs.QueryParam, refactor your code to use JAX-RS-annotated bean properties or fields instead. We can add an @javax.annotation.PostConstruct annotated method to help construct your object.
Additionally, JAX-RS root resource and provider classes must have a JCDI specified scope. Scopes control the lifecycle of a JCDI managed bean. Root resource classes can have any valid scope such as @javax.enterprise.context.RequestScoped, which makes the JAX-RS root resource class behave the same as in a non-JCDI enabled application. The javax.ws.rs.core.Application subclasses and JAX-RS providers must have the @javax.enterprise.context.ApplicationScoped annotation.
You might want to use JCDI to more quickly and easily develop the application, as well as increase the testability of your code. JCDI enables modern programming techniques such as dependency injection, an event-based programming model, and a more aspect-oriented approach towards cross-cutting concerns. Developers can use aspect-oriented programming to cleanly add functionality that is not part of the core business logic to a method. For example, one cross cutting concern is logging. Some developers need to log the entry and exit of every single time a certain business method is called in an application. Developers now can use JCDI functionality such as method interceptors and decorators to more cleanly add this functionality. Developers can use dependency injection to more easily insert their own mock implementations during unit testing. The decoupling of previously hard coded dependencies allows developers to more easily test individual components.
JCDI beans can inject Enterprise JavaBeans (EJBs) and use @javax.annotation.Resource injections to inject Java EE resources. EJBs can also be JCDI beans. EJBs with annotations such as @javax.ejb.Stateless can also use JCDI dependency injection and other JCDI features. The EJBs keep their transactional and other EJB features.
New feature: Java Contexts and Dependency Injection (JCDI)
is a new Java EE 6 feature.
It can change the programming model to make applications easier to develop while increasing maintainability. JAX-RS developers can use JCDI features, such as @javax.inject.Inject support, in root resource and provider classes.New feature:
Procedure
- Configure the development environment.
- Define the resources in JAX-RS web applications.
- Configure the JAX-RS application.
- Implementing JAX-RS resources with JCDI functionality.
- Assemble JAX-RS web applications.
- Deploy JAX-RS web applications.
Results
You have enabled an enterprise bean so that JAX-RS resources with JCDI functionality are exposed for consumption.