I'm currently learning about RESTful web service implementation using Java in my development environment, which consists of Netbeans IDE with GlassFish v3.
Within my project, I have a specific page URL called /inventoryList, which is mapped to the InventoryApp.java servlet in the web.xml file.
Here's an example of the web.xml configuration:
<?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>inventoryServlet</servlet-name>
<servlet-class>local.test.servlet.InventoryApp</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>inventoryServlet</servlet-name>
<url-pattern>/inventoryList</url-pattern>
</servlet-mapping>
</web-app>
The purpose of this servlet is to retrieve inventory item information from a database and display it on the corresponding JSP page.
In the provided example, the JSP file named inventory.jsp contains the necessary logic to handle the retrieval and display of inventory items:
<%@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">
//Ajax code here
</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 in the provided JSP file, each inventory amount value is displayed as a link. When clicked, an Ajax call is triggered to retrieve additional details about the specific inventory item.
The corresponding REST service implementation for handling this Ajax request is shown in the provided example code:
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("Handling GET request");
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;
}
}
When testing the implemented code, everything seems to be working fine initially. However, there is an issue where the retrieved inventory data briefly appears on the page and then disappears.
After investigating with tools like Firebug and examining the GlassFish v3 server logs, it was discovered that the InventoryApp.java servlet is being called again at the end of the process, which triggers a redirect to the /inventoryList page.
This behavior seems strange because Ajax requests should not cause the entire page to refresh. The issue might be related to the mixing of servlets and RESTful services in this project.
If anyone has any insights or suggestions on how to resolve this issue, your help would be greatly appreciated as I have been trying to resolve this for several days now.
For reference, here's an example snippet from the 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 {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
InventoryDao invDao = new InventoryDao();
List<Inventory> invList = invDao.findAll();
System.out.println("================= do get servelt ===" + invList.get(0));
request.setAttribute("inventoryList", invList);
request.getRequestDispatcher("inventory.jsp").forward(request, response);
}
}