Using the Session Synchronization Interface

An EJB that is a session bean can optionally implement the session synchronization interface, to be notified by the container of the transactional state of the bean. The following methods are specified in the javax.ejb.SessionSynchronization interface:

afterBegin

public abstract void afterBegin() throws RemoteException

The afterBegin() method notifies a session Bean instance that a new transaction has started, and that the subsequent methods on the instance are invoked in the context of the transaction.

A bean can use this method to read data from a database and cache the data in the bean's fields.

This method executes in the proper transaction context.

beforeCompletion

public abstract void beforeCompletion() throws RemoteException

The container calls the beforeCompletion() method to notify a session bean that a transaction is about to be committed. You can implement this method to, for example, write any cached data to the database.

afterCompletion

public abstract void afterCompletion(boolean committed) throws RemoteException

The container calls afterCompletion() to notify a session bean that a transaction commit protocol has completed. The parameter tells the bean whether the transaction has been committed or rolled back.

This method executes with no transaction context.

Example 7-13 SessionSynch Example

In order for the container to invoke your bean implementation before and after every transaction, your bean must implement the SessionSynch interface.

package employeeServer;

import employee.*;

import javax.ejb.SessionBean;
import javax.ejb.CreateException;
import javax.ejb.SessionContext;
import java.rmi.RemoteException;

import java.sql.SQLException;

public class EmployeeBean implements SessionBean implements SessionSynch
{
  // Methods of the Employee interface
  public EmployeeInfo getEmployee (String name)
       throws RemoteException, SQLException
  {
    int empno = 0;
    double salary = 0.0;
    #sql { select empno, sal into :empno, :salary from emp
                  where ename = :name };

    return new EmployeeInfo (name, empno, salary);
  }

  public void updateEmployee (EmployeeInfo employee)
       throws RemoteException, SQLException
  {
     #sql { update emp set ename = :(employee.name),
                   sal = :(employee.salary)
                   where empno = :(employee.number) };
    return;
  }

  // Methods of the SessionBean
  public void ejbCreate () throws RemoteException, CreateException {}
  public void ejbRemove () {}
  public void setSessionContext (SessionContext ctx) {}
  public void ejbActivate () {}
  public void ejbPassivate () {}

  public void beforeBegin() 
  {
    ... perform work ...
  }
  public void afterCompletion()
  {
    ... perform work ...

  }
}

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