catalogservlet.java

EJB实践的服务器是用SUN的服务器

package examples;

import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.naming.*;

/**
 * This servlet displays a catalog of products to
 * the end-user.
 *
 * By the time this servlet is called, the user has
 * logged in (via the Login servlet), and has a shopping
 * cart started (i.e. Cart bean).  Since this servlet is
 * pooled and re-used for different user requests, the
 * servlet code does not store any information specific to
 * any user.  Rather, we store a reference to the user's
 * Cart in the user's HttpSession object, which is
 * globally accessible to all servlets.
 */
public class CatalogServlet 
    extends HttpServlet 
{
    private CatalogHome catalogHome = null;

    /**
     * The servlet engine calls this method once to
     * initialize a servlet instance.
     *
     * In the body of this method, we need to acquire the
     * EJB Catalog Home Object.
     */
    public void init(ServletConfig config) 
        throws ServletException 
    {
        super.init(config);

        try 
        {
            /*
             * Get the initial JNDI context using the
             * above startup params.
             */
            Context ctx = new InitialContext();

            /*
             * Look up the Catalog Home Object.
             */
            catalogHome = (CatalogHome)ctx.lookup("ejb/CatalogHome");
        } 
        catch (Exception e) 
        {
            e.printStackTrace();
        }
    }

    /**
     * The servlet engine calls this method when the user's
     * desktop browser sends an HTTP request.
     */
    public void service (HttpServletRequest request, HttpServletResponse response)
	throws ServletException, IOException 
    {
        Vector	products=null;
        try 
        {
            /*
             * Get the user's HttpSession, and from that get
             * the user's current cart.
             */
            HttpSession session = request.getSession(false);
            if (session == null) 
            {
                /*
                 * Redirect user to login page if he
                 * doesn't have a session.
                 */
                response.sendRedirect(response.encodeRedirectURL("/jasmine/login"));
                return;
            }

            Object obj = session.getAttribute("cart");
            if (obj == null) 
            {
                /*
                 * Redirect user to login page if he
                 * doesn't have a session.
                 */
                response.sendRedirect(response.encodeRedirectURL("/jasmine/login"));
                return;
            }
            Cart cart = (Cart) obj;
            String productIDToAdd = request.getParameter("Buy");
            products = (Vector)session.getAttribute("products");
            String productId = (String)request.getParameter("productId");  			

            /*
             * If user wants to purchase something (via
             * the URL parameter 'Buy'), add the desired
             * product item to the cart.
             */
			
            if (productIDToAdd != null) 
            {               
                /*
                 * Creates LineItem, and add to the cart.
                 */
                try 
                {
                    ProductItem item = getProductItem(products,productIDToAdd);
                    cart.add(new LineItem(item,1,0));
                    // Set a flag so that JSP knows which product we purchased
                    request.setAttribute("ProductPurchased", item.getName());
                    // Forwards the request to the catalog JSP
                    this.getServletContext().getRequestDispatcher("/catalog.jsp").forward(request, response);
                    return;
                } 
                catch (Exception e) 
                {
                    throw new ServletException(e.toString());
                }                                
            }
            /*
             * If user wants to view the product details (via
             * the URL parameter 'productId')
             */
            else if(productId != null)
            {
                //Retrieves the product item from the prducts vector and pass it in request object.
                request.setAttribute("productItem",getProductItem(products,productId));
                // Forwards the request to the productInfo JSP
                this.getServletContext().getRequestDispatcher("/productInfo.jsp").forward(request, response);
                return;
            }
            /*
             * If products vector = null,Retrieves productItems vector
             * from Catalog stateless session bean and put it in the
             * HttpSession. we may need to put this vector in
             * application level instead of session.
             */
            else 
            {
                if(products == null)
                {
                    Catalog catalog = catalogHome.create();
                    products = catalog.getProductItemList();
                    session.setAttribute("products", products);
                }	
                // Forwards the request to the catalog JSP
                this.getServletContext().getRequestDispatcher("/catalog.jsp").forward(request, response);
                return;
            }
        }
        catch (Exception e) 
        {
            e.printStackTrace();
        }
    }

    /**
     * Returns the productitem for the given product id,if it is in the vector
     */
   
    private ProductItem getProductItem(Vector products,String productIDToAdd)
    {
        int size = products.size();
        for(int i=0; i < size; i++)
        {
            ProductItem item = (ProductItem)products.elementAt(i);
            if(item.getProductID().equals(productIDToAdd))
            {
                return item;
            }
        }
        return null;
    }

    public String getServletInfo() 
    {
        return "The Catalog servlet adds products to the user's " +
            "cart and prints the catalog.";
    }
}