The pattern of invoking EJB3 method from JSF managed bean

-----------Web Layer--------------------------------------------------

/*
* XXX managed bean
*/
...

public class XXXBean extends MyManagedBean
{
    // Session bean JNDI name
    private static final String EJB_PRODUCT_SESSION= "ProductSession";

    // Session bean remote interface
    ProductSessionRemote productSession;

    // Session bean local interface
    //ProductSessionLocal productSession;

    public XXXBean
    {
        try
        {
            productSession=(ProductSessionRemote)ServiceLocator.getInstance().getEJB(EJB_PRODUCT_SESSION);
        }
        catch(Exception) {
            ...
        }
        …
     }

    public String findProduct(…)
    {
         …
         try {
             …
              product=productSession.findProductById(productId);
             …
          }
         catch(Exception e)
         {
             processException(e,productId);
             return null; // go current page
          }
         …
          return “yyyy”;
    }

    public String createProduct(…)
    {
         …
         try {
             …
              product=productSession.createProduct(product);
             …
          }
         catch(Exception e)
         {
             int ret=processException(e);

             // process nivagation according to your exception handling strategy
             if ( ret== APPLICATION_EXCEPTION )
                return “xxxx”; // go error page
             else
                …
          }
         …
          return “yyyy”;
     }
     …
}


/*
* MyManagedBean, which is extended by all the managed beans.
*/
...

public class MyManaedBean
{
    …….

   /*
     * Process exception for invocation session bean
     */
    protected int processException(Exception e,Object... args)
    {
        if( e==null )
            return -1;
       
        if (e instanceof AppException) // application exception
        {
             addMessage(FacesMessage.SEVERITY_ERROR,e.getMessage(),args);
             return APPLICATION_EXCEPTION;
        }
        else
        if (e instanceof EJBAccessException) // no permission exception
        {
             addMessage(FacesMessage.SEVERITY_ERROR,CmmwebKeys.NO_PERMISSION_FAILURE);
             return NO_PERMISSION_EXCEPTION;
        }
        else // exception
        {
             addMessage(FacesMessage.SEVERITY_ERROR,CmmwebKeys.GENERAL_FAILURE);
             return OTHER_EXCEPTION;
        }
    }

    // handle message
    protected void addMessage(FacesMessage.Severity severity,String bundleMessageName,Object... args)
    {
        String message = getBundleMessage(bundleMessageName,args);
        FacesContext.getCurrentInstance().addMessage(null,new FacesMessage(severity,message,message));
    }

    ...
}


/*
* ServiceLocator.java
*
* Created on 19 October 2006, 09:45
* @author xfang
*
*/
...

public class ServiceLocator {
   
    private InitialContext ic;
    private Map cache;
   
    private static ServiceLocator me;
   
    static {
        try {
            me = new ServiceLocator();
        } catch(NamingException se) {
            throw new RuntimeException(se);
        }
    }
   
    private ServiceLocator() throws NamingException  {
        ic = new InitialContext();
        cache = Collections.synchronizedMap(new HashMap());
    }
   
    public static ServiceLocator getInstance() {
        return me;
    }
   
    private Object lookup(String jndiName) throws NamingException {
        Object cachedObj = cache.get(jndiName);
        if (cachedObj == null) {
            cachedObj = ic.lookup(jndiName);
            cache.put(jndiName, cachedObj);
        }
        return cachedObj;
    }
   
    /**
     * will get the ejb3. If this ejb home factory has already been
     * clients need to cast to the type of EJBHome they desire
     *
     * @return the EJB3 corresponding to the homeName
     */
    public Object getEJB(String jndiEJBName) throws NamingException {
        Object objref = lookup(jndiEJBName);
        return objref;
    }
}

-------------EJB Layer------------------------------------------------

/*
* Product Session Bean
*/
...

@Stateless
@TransactionManagement(value = TransactionManagementType.CONTAINER)

public class ProductSession implements ProductSessionLocal,ProductSessionRemote
{
    @PersistenceContext(unitName="mydb")
    private EntityManager em;

   /**
     * Find a product entity by its ID
     */
    public Product findProductById(long id) throws AppException,Exception
    {
Product product = null;

try
         {
    product=(Product)em.find(Product.class,id);  // find from database

             initProduct(product);// initialize lazy-loaded property
}
         catch(Exception e) {
    throw e;
}

return product;
    }

   /**
     * create a new product
     */
    public Product createProduct(Product p) throws AppException,Exception
    {
Product product = p;

try {

             if ( !validateXXX(product) ) // validate failed!
             {
                 throw new AppException("AppException.xxx.0001");
             }
             ...
         
             em.persist(product); // save to database

    em.refresh(product); // re-initialize entity

    initProduct(product); // initialize lazy-loaded property
}
         catch (Exception e) {
    throw e;
}

return product;
    }
}


/*
* Product Session Bean Local interface
*/
...

import javax.ejb.Local;

@Local
public interface ProductSessionLocal
{
    Product findProductById(long id) throws AppException,Exception;
    Product createProduct(Product product) throws AppException,Exception;
}

/*
* Product Session Bean Remote interface
*/
...

import javax.ejb.Remote;

@Remote
public interface ProductSessionRemote
{
    Product findProductById(long id) throws AppException,Exception;
    Product createProduct(Product product) throws AppException,Exception;
}
------------------------------------------------------------------------