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Simplify enterprise Java development with EJB 3.0, Part 1

Use annotations to develop POJO services

By Michael Juntao Yuan, JavaWorld.com, 08/15/05

Page 6 of 6

 @Stateless
@SecurityDomain("other")
public class CalculatorBean implements Calculator {


  @RolesAllowed({"AdminUser"})
  public void addFund (String name, double growthrate) {
    // ... ...
  }


  @RolesAllowed({"AdminUser"})
  public void addInvestor (String name, int start, int end) {
    // ... ...
  }


  @PermitAll
  public Collection <Fund> getFunds () {
    // ... ...
  }
  
  // ... ...


  @RolesAllowed({"RegularUser"})
  public double calculate (int fundId, int investorId, 
                                       double saving) {
    // ... ...
  }
}

Generic interceptors

Both transaction and security services can be considered runtime interceptors managed by the container. The container intercepts the method calls from the EJB stub and applies transaction context or security constraints around the calls.

In EJB 3.0, you can extend the container services by writing your own interceptors. Using the @AroundInvoke annotation, you can specify any bean method as the interceptor method that will execute before and after any other bean method runs. In the following example, the log() method is the interceptor that profiles and logs the execution time of other bean methods:

 @Stateful
public class CalculatorBean implements Calculator {


  // Bean methods that are to be intercepted by "log()"
  // ... ...
  
  @AroundInvoke
  public Object log (InvocationContext ctx)
                            throws Exception {


    String className = ctx.getBean().getClass().getName();
    String methodName = ctx.getMethod().getName();
    String target = className + "." + methodName + "()";


    long start = System.currentTimeMillis();
    System.out.println ("Invoking " + target);
    try {
      return ctx.proceed();
    } catch(Exception e) {
      throw e;
    } finally {
      System.out.println("Exiting " + target);


      cal.setTrace(cal.getTrace() + "
" +
                   "Exiting " + target);
      long time = System.currentTimeMillis() - start;
      System.out.println("This method takes " +
                          time + "ms to execute");
    }
  }
}

What's next?

In Part 1 of this series, I discussed the general POJO-based programming model for EJB 3.0 and how to develop loosely coupled service objects in EJB 3.0. In Part 2, I will discuss another major aspect of EJB 3.0: managed POJO persistence. Stay tuned.

About the author

Read more about Enterprise Java in JavaWorld's Enterprise Java section.