Why my Ajax call refresh page? (i.e. calling servlet again)_问答_开发者

I'm studying RESTful web service using Java. My environment is using Netbean with GlassFish v3.

I have a page URL /inventoryList which is URL mapped to InventoryApp.java servlet in web.xml

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/j2ee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
    version="2.4">
    <servlet>
        <servlet-name>inventory servlet</servlet-name>
        <servlet-class>local.test.servlet.InventoryApp</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>inventory servlet</servlet-name>
        <url-pattern>/inventoryList</url-pattern>
    </servlet-mapping>
</web-app>

In the servlet, it obtains list of inventory item info from DB and display to the JSP page.

inventory.jsp

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
   "http://www.w3.org/TR/html4/loose.dtd">
<%@ taglib prefix="c" uri="http://java.sun.com/jstl/core_rt" %>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>JSP Page</title>

        <script type="text/javascript">

        function ajaxGet(inventoryId) {
            alert(inventoryId);
            var xmlHttp = new XMLHttpRequest();
            xmlHttp.onreadystatechange = function() {

                alert('sigh');

                if(xmlHttp.readyState == 4 && xmlHttp.status == 200) {
                    alert('ready 4');
                    alert('After ready4 ===> ' + xmlHttp.responseText);

                    displayInventoryHtml(xmlHttp);

                }
            }
            var url = "resources/inventory/" + inventoryId;
            xmlHttp.open("GET", url, true);
            xmlHttp.send(null);
        }

        function displayInventoryHtml(responseAjax) {
            document.getElementById('inventoryItem').innerHTML = responseAjax.responseText;
        }

        </script>

    </head>
    <body>
        <h1>Inventory page</h1>

        <table border="1" cellspacing="1" cellpadding="5">
            <th>id</th>
            <th>amount</th>
            <c:forEach items="${inventoryList}" var="inv" >
                <tr>
                    <td>${inv.id}</td>
                    <td><a href="" onclick="ajaxGet(${inv.id})">${inv.amount}</a></td>
                </tr>
            </c:forEach>
        </table>
        <hr />
        <div id="inventoryItem">
        </div>


    </body>
</html>

As you can see the inventory.jsp would successfully output the list of inventory item.

So far so good.

Here, I made the output of inventory amount value to be a link to Ajax call.

<td><a href="" onclick="ajaxGet(${inv.id})">${inv.amount}</a></td>

It calls HTTP GET method and REST service (code shown below) will get inventory data of specified id (database primary id) and I put the Ajax responseText into the div (id=inventoryItem)

InventoryResource.java

package local.test.jaxrs;

import java.util.List;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.UriInfo;
import javax.ws.rs.Consumes;
import javax.ws.rs.DELETE;
import javax.ws.rs.PUT;
import javax.ws.rs.Path;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import local.test.dao.InventoryDao;
import local.test.session.Inventory;

@Path("/inventory")
public class InventoryResource {
    @Context
    private UriInfo context;

    /** Creates a new instance of InventoryResource */
    public InventoryResource() {
    }


    @Path("{inv_id}")
    @GET
    @Produces("text/html")
    public String getJson(@PathParam("inv_id") String inventory_id) {
        System.out.println("GET is being handled");

        Inventory invBean = new Inventory(Integer.valueOf(inventory_id));
        InventoryDao invDao = new InventoryDao();
        List<Inventory> inv = invDao.findById(invBean);

        String html = "<b>" + inv.get(0).getId() + "</b><br /><b>" + inv.get(0).getAmount() + "</b><br />";

        return html;

    }
}//end class

When I test this开发者_StackOverflow社区 code, everything works just fine. The Ajax successfully get data and insert into the HTML DIV tag and the inventory data shows up for half second and disappear.

Using firebug and looking at glassfish v3 server log, I figure that at the end, it is calling InventoryApp.java servlet AGAIN which cause the page to redirect to /inventoryList

I know Ajax is partial request and should not cause page to refresh.

I'm stack in this for few days now, could anyone give me hint what's going on? I'm not sure if it is practical to mix servlet and web.xml with REST like I do.

FYI, my InventoryApp.java servlet code

package local.test.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import local.test.dao.InventoryDao;
import local.test.session.Inventory;


@WebServlet(name="InventoryApp", urlPatterns={"/InventoryApp"})
public class InventoryApp extends HttpServlet {

    /** 
     * Processes requests for both HTTP <code>GET</code> and <code>POST</code> methods.
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        try {

        } finally { 
            out.close();
        }
    } 

    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /** 
     * Handles the HTTP <code>GET</code> method.
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        InventoryDao invDao = new InventoryDao();
        List<Inventory> invList =  invDao.findAll();

        //this list looks ok...
        System.out.println("================= do get servelt ===" + invList.get(0));

        request.setAttribute("inventoryList", invList);
        request.getRequestDispatcher("inventory.jsp").forward(request, response);

        //processRequest(request, response); //commented not sure what it is..
    } 
}//end class

<a href="" onclick="ajaxGet(${inv.id})">${inv.amount}</a>

remove the href attribute

<a onclick="ajaxGet(${inv.id})">${inv.amount}</a>

or cancel the promotion of the click event

<a href="" onclick="ajaxGet(${inv.id}); return false;">${inv.amount}</a>

Why my Ajax call refresh page? (i.e. calling servlet again)

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