Integrate EJBs with Web Module Model Objects

When developing the presentation logic, we were deliberate in not only following a model-view-controller design, but in establishing a fa ade for the model part of the design. This fa ade is made up of a simple Java object that represents – or front-ends, if you will – each of our EJBs. This allowed the presentation logic to be built up independently of the business logic development. We introduced these model objects at the beginning of the chapter, so we will simply list them quickly here as a reminder:

• CartModel

• OrderModel

• InventoryModel

• CustomerModel

Now that we have implemented our business logic as a set of EJBs, it is time to connect them to the model objects.

Implement the Model Code

Since each model object will delegate onto an associated EJB, we will need code that enables the model object to look up the appropriate EJB home in JNDI. We will introduce a specific method in each model object for that purpose. The resulting home reference can be cached for later use. The getShoppingCartHome() method and related code in the CartModel class shows how to do this:

 import javax.naming.InitialContext; import javax.ejb.EJBException; import java.util.Vector; public class CartModel {   private final static String SHOPPINGCART_HOME_NAME =     "java:comp/env/ejb/plantsby/ShoppingCartHome";   private static ShoppingCartHome shoppingCartHome;   private ShoppingCartHome getShoppingCartHome() {     if ( shoppingCartHome == null ) {        try {          InitialContext ctx= new InitialContext();          shoppingCartHome= (ShoppingCartHome)           ctx.lookup(SHOPPINGCART_HOME_NAME);       } catch (Exception e) {         throw new EJBException(e);       }       return shoppingCartHome;     } else {       return shoppingCartHome;     }   }  }  

Each model object will have similar JNDI lookup code for its own specific EJB home lookup.

Since a CartModel will delegate to exactly one ShoppingCart session bean, we can create the session bean in the CartModel constructor. The remaining CartModel methods do simple delegation onto the session bean:

 private ShoppingCart shoppingCart; CartModel() {   try {     shoppingCart= getShoppingCartHome().create();   } catch (Exception e) {     throw new EJBException(e);   } } public void addItem(StoreItem si) {   shoppingCart.addItem(si); } public Vector getItems() {   return shoppingCart.getItems(); } 

InventoryModel

In doing the integration of the InventoryModel object with the Inventory EJB, we run into a little snafu. The presentation logic uses a String type for category, whereas the business logic uses an integer. We cannot possibly over-stress the importance of a rigorous design review process. However, rather than going back and fixing it for the purposes of our development presentation, we opted to leave it in for example's sake, since these kinds of things can really happen in software development. Hey, we're only human (wink)!

So let's add a method to map category strings to integers:

 private int getCategoryKeyFromString(String category) {   int icategory;    if ( category.equals("flowers") ) {     icategory = Inventory.FLOWERS;   } else if ( category.equals("fruit") ) {     icategory = Inventory.FRUIT;   } else if ( category.equals("trees") ) {     icategory = Inventory.TREES;   } else if ( category.equals("accessories") ) {     icategory = Inventory.ACCESSORIES;   } else throw new EJBException("category not valid – category = " + category);     return icategory;   } } 

The InventoryModel uses the StoreItem class to represent inventory items, so that it does not expose the Inventory EJB interface. That means will need additional helper classes to convert an Inventory collection to StoreItems:

 private StoreItem InventoryToStoreItem(Inventory inv) {   return new StoreItem(inv); } private Collection InventoryToStoreItems(Collection c) {   Vector v = new Vector();   try {     Iterator i = c.iterator();     while ( i.hasNext() ) {       Inventory inv = (Inventory) i.next();       v.add(InventoryToStoreItem(inv));     }     return v;   } catch (Exception e) {     throw new EJBException(e);   } } 

The InventoryModel offers two finder methods, which do nothing more than delegate to InventoryHome finders, then convert the resulting Inventory objects to StoreItem objects:

 public Collection findByCategory(String category) {   try {     int icategory = getCategoryKeyFromString(category);     Collection c = getInventoryHome().findByCategory(icategory);         return InventoryToStoreItems(c);   } catch (Exception e) {     throw new EJBException(e);   } } public StoreItem findById(String id) {   try {     InventoryKey key = new InventoryKey(id);     Inventory inv = (Inventory) getInventoryHome().findByPrimaryKey(key);       return InventoryToStoreItem(inv);   } catch (Exception e) {     throw new EJBException(e);   } } 

and of course here's the EJB lookup:

 private final static String INVENTORY_HOME_NAME=    "java:comp/env/ejb/plantsby/InventoryHome"; private static InventoryHome inventoryHome; private InventoryHome getInventoryHome() {   if ( inventoryHome == null ) {      try {       InitialContext ctx = new InitialContext();       inventoryHome = (InventoryHome) ctx.lookup(INVENTORY_HOME_NAME);     } catch (Exception e) {       e.printStackTrace();       throw new EJBException(e);     }     return inventoryHome;   } else {     return inventoryHome;   } } 

OrderModel

The OrderModel object has only a single business method, addOrder(), which is a simple delegation to the Order EJB. Note we have not implement supported for credit cards. We'll just fake it for now. Adding credit-card support is beyond what we'll cover in this chapter:

 public String addOrder(CustomerInfo c, Vector orderItems) {    try {     Order o = getOrderHome().create(c.getEmail(), c.getName(), c.getAddr1(),                                      c.getAddr2(), c.getCity(), c.getState(),                                      c.getZipcode(), c.getPhone(), c.getName(),                                      c.getAddr1(), c.getAddr2(), c.getCity(),                                      c.getState(), c.getZipcode(), c.getPhone(),                                      "NO CREDIT CARD", "NO CC NUMBER",                                      "NO CC MONTH", "NO CC YEAR",                                     "NO CARD HOLDER", 1, // shipping method                                     orderItems);     return o.getID();    } catch (Exception e) {     throw new EJBException(e);   } } 

and the getOrderHome() method and support:

 private final static String ORDER_HOME_NAME =    "java:comp/env/ejb/plantsby/OrderHome"; private static OrderHome inventoryHome;      private OrderHome getOrderHome() {   if ( inventoryHome == null ) {      try {        InitialContext ctx= new InitialContext();        inventoryHome= (OrderHome) ctx.lookup(ORDER_HOME_NAME);     }  catch (Exception e) {        e.printStackTrace();        throw new EJBException(e);     }       return inventoryHome;   } else {     return inventoryHome;   } } 

CustomerModel

The customer model has two methods to implement: one to add a customer; one to find one. These methods will primarily use the Customer EJB's finder methods. The addCustomer() method is the exception: it uses the Customer method update() to update an existing Customer to account for changes the user may have made to their name, address, etc:

 public void addCustomer(CustomerInfo i) {   CustomerKey key = new CustomerKey(i.getEmail());   try {           Customer c = getCustomerHome().findByPrimaryKey(key);       c.update( i.getFirstName(), i.getLastName(),i.getAddr1(), i.getAddr2(),                  i.getCity(), i.getState(), i.getZipcode(), i.getPhone() );   } catch ( FinderException e ) {     try {       Customer c = getCustomerHome().create(key, "PASSWORD", i.getFirstName(),                                             i.getLastName(), i.getAddr1(),                                              i.getAddr2(), i.getCity(),                                              i.getState(),i.getZipcode(),                                              i.getPhone());       } catch ( CreateException ex) {       throw new EJBException("Could not create new customer");     }   }   } public CustomerInfo getCustomer(String emailKey) {   CustomerKey key = new CustomerKey(emailKey);   try {           Customer c= getCustomerHome().findByPrimaryKey(key);     CustomerInfo ci= new CustomerInfo();             ci.setEmail(c.getCustomerId());     ci.setFirstName(c.getFirstName());      ci.setLastName(c.getLastName());      ci.setAddr1(c.getAddr1());     ci.setAddr2(c.getAddr2());     ci.setCity(c.getCity());     ci.setState(c.getState());     ci.setZipcode(c.getZip());     ci.setPhone(c.getPhone());           return ci;   } catch ( FinderException e ) {     throw new EJBException("Could not find customer with key " + emailKey);   } } 

Finally, the EJB lookup:

 private final static String Customer_HOME_NAME =    "java:comp/env/ejb/plantsby/CustomerHome"; private static CustomerHome CustomerHome;      private CustomerHome getCustomerHome() {   if ( CustomerHome == null ) {      try {       InitialContext ctx = new InitialContext();       CustomerHome= (CustomerHome) ctx.lookup(Customer_HOME_NAME);     } catch (Exception e) {       e.printStackTrace();       throw new EJBException(e);     }       return CustomerHome;   } else {     return CustomerHome;   } } 

Declare EJB References

Finally, and as the last step in connecting our EJBs to the model beans in our web module, let's declare the EJB references we require in PlantsByWebSphereWAR. Do this by opening the Deployment Descriptor editor for the PlantsByWebSphereWAR. Select the Resources tab in the editor.

The screen layout is slightly different because it's a web module, but otherwise it's same idea as when we linked up the EJB references for the EJB module:

Choose the EJB Local tab, click the Add button Complete the web module reference declarations based on the following table:

Name	Local Home	Local
ejb/plantsby/ShoppingCartHome	com.ibm.pbw.ejb.ShoppingCartHome	com.ibm.pbw.ejb.ShoppingCart
ejb/plantsby/InventoryHome	com.ibm.pbw.ejb.InventoryHome	com.ibm.pbw.ejb.Inventory
ejb/plantsby/OrderHome	com.ibm.pbw.ejb.OrderHome	com.ibm.pbw.ejb.Order
ejb/plantsby/CustomerHome	com.ibm.pbw.ejb.CustomerHome	com.ibm.pbw.ejb.Customer