簡化一個(gè)編程模型并沒有減少它的功能。簡化只是把復(fù)雜的邏輯隱藏到了框架代碼或可重用的組件中去了。根本上，它是把復(fù)雜的東西從需要應(yīng)用開發(fā)者直接管理的地方轉(zhuǎn)移到了大多數(shù)開發(fā)者看不到的地方。

public interface Calculator {

  public double calculate (int start, int end, 
                double growthrate, double saving);

}

@Stateless
public class CalculatorBean implements Calculator {

  public double calculate (int start, int end, 
                    double growthrate, double saving) {
    double tmp = Math.pow(1. + growthrate / 12., 
                          12. * (end - start) + 1);
    return saving * 12. * (tmp - 1) / growthrate;
  }

}

@Stateless
@Local ({Calculator.class})
@Remote ({RemoteCalculator.class})
public class CalculatorBean implements Calculator, RemoteCalculator {

  public double calculate (int start, int end, 
                           double growthrate, double saving) {
    double tmp = Math.pow(1. + growthrate / 12., 12. * (end - start) + 1);
    return saving * 12. * (tmp - 1) / growthrate;
  }

  public String getServerInfo () {
    return "This is the JBoss EJB 3.0 TrailBlazer";
  }
}

InitialContext ctx = new InitialContext();
cal = (Calculator) ctx.lookup(Calculator.class.getName());

double res = cal.calculate(start, end, growthrate, saving); 

@Stateful
public class CalculatorBean implements Calculator, Serializable {

    // ... ...
    
    @PostConstruct
    public void initialize () {
        // Initializes the history records and load
        // necessary data from database etc.
// 初始化歷史記錄，并從數(shù)據(jù)庫中裝入必需的數(shù)據(jù)。
    }  
    
    @PreDestroy
    public void exit () {
        // Save history records into database if necessary.
// 如有必要?jiǎng)t將歷史記錄保存至數(shù)據(jù)庫中
    }   
    
    @Remove
    public void stopSession () {
        // Call to this method signals the container
        // to remove this bean instance and terminates
        // the session. The method body can be empty.
// 調(diào)用這個(gè)方法來通知容器將bean實(shí)例移除并中止session.
// 這個(gè)方法可以為空。
    }
    
    // ... ...
}

@MessageDriven(activateConfig =
{
  @ActivationConfigProperty(propertyName="destinationType",
    propertyValue="javax.jms.Queue"),
  @ActivationConfigProperty(propertyName="destination",
    propertyValue="queue/mdb")
})
public class CalculatorBean implements MessageListener {

  public void onMessage (Message msg) {
    try {
      TextMessage tmsg = (TextMessage) msg;
      Timestamp sent =
          new Timestamp(tmsg.getLongProperty("sent"));
      StringTokenizer st =
          new StringTokenizer(tmsg.getText(), ",");

      int start = Integer.parseInt(st.nextToken());
      int end = Integer.parseInt(st.nextToken());
      double growthrate = Double.parseDouble(st.nextToken());
      double saving = Double.parseDouble(st.nextToken());

      double result =
          calculate (start, end, growthrate, saving);
      RecordManager.addRecord (sent, result);

    } catch (Exception e) {
      e.printStackTrace ();
    }
  }

  // ... ...
}

public class CalculatorMDB implements MessageListener {

  @EJB Calculator cal;
  
  // Use the cal variable
  // ... ...
}

public class CalculatorMDB implements MessageListener {

  Calculator cal;
  
  @EJB
  public void setCal (Calculator cal) {
    this.cal = cal;
  }
  
  // Use the cal variable
// 使用cal變量
  // ... ...
}

@Resource
TimerService tms;

@Resource
SessionContext ctx;

@Resource (name="DefaultDS")
DataSource myDb;

@Resource (name="ConnectionFactory")
QueueConnectionFactory factory;

@Resource (name="queue/A")
Queue queue;

@Stateless
public class CalculatorBean implements Calculator {

  // ... ...

  @TransactionAttribute(TransactionAttributeType.REQUIRED)
  public void updateExchangeRate (double newrate) throws Exception {
    // Update the database in a loop.
// 在循環(huán)中更新數(shù)據(jù)庫
    // ... ...
    // The Operations in the loop must all be successful or
    // the database is not updated at all.
// 循環(huán)中的操作必須全部成功或者根本不更新。
  }
}

@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) {
    // ... ...
  }
}

@Stateful
public class CalculatorBean implements Calculator {

  // Bean methods that are to be intercepted by "log()"
  // bean方法將被log()方法攔截
// 
  // ... ...
  
  @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");
    }
  }
}

（出處：http://m.survivalescaperooms.com）