Issue
Somehow, the <c:out> tag is not working at all. It doesn't show any alerts and it's just blank. It's like I never added the tag into the file. Here's my code:
Connector.java:
package connect;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import javax.servlet.ServletContext;
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 javax.servlet.http.HttpSession;
import products.Product;
/**
* Servlet implementation class Connector
*/
@WebServlet("/Connector")
public class Connector extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public Connector() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
@SuppressWarnings({ "unchecked", "null", "unused" })
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
PrintWriter out = response.getWriter();
try {
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
String url = "jdbc:sqlserver://\\\\.\\pipe\\MSSQL$SQLEXPRESS\\sql\\query:8888;databaseName=ShoppingDB";
Connection con = DriverManager.getConnection(url,"sa","33887899");
Statement stmt = con.createStatement();
ArrayList<Product> pro=new ArrayList<Product>();
ResultSet rs=stmt.executeQuery("select * from Products");
Product p = new Product();
while(rs.next()) {
p.setId(rs.getInt("product_id"));
p.setName(rs.getString("product_name"));
p.setDes(rs.getString("product_des"));
p.setPrice(rs.getInt("product_price"));
p.setSrc(rs.getString("product_img_source"));
p.setType(rs.getString("product_type"));
p.setBrand(rs.getString("product_brand"));
p.setAmount(1000);
pro.add(p);
}
Product re;
String name=request.getParameter("search");
for(int i =0;i<pro.size();i++) {
if(pro.get(i).getName()==name) {
re=pro.get(i);
break;
}
}
p=pro.get(0);
ServletContext context=getServletContext();
context.setAttribute("p", p);
}catch(Exception e) {
out.println(e);
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
Home.jsp
<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
<!DOCTYPE html>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt" %>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Insert title here</title>
<link rel="stylesheet" href="Style.css">
</head>
<body style="background-color:#f5f5f5;">
<h1 style="text-align:center">PRJ321X_202x</h1>
<div id="nav">
<button class="navbtn">Home</button>
<button class="navbtn">Products</button>
<button class="navbtn">About Us</button>
<button class="navbtn" style="float:right;" onclick="location.href='Login.jsp'">Log in</button>
<form style="float:right;" method="Post" action="Connector">
<input name="search" id="search" type="text" placeholder="Search..">
<input type="submit" style="display:none">
</form>
</div>
<script src="Script.js"></script>
<div style="float:left;width:75%;margin-right:5px;" id="products">
<div>
<c:out value="${p.id}"/>
</div>
</div>
<div style="float:left;width:24%">
<div style="background-color:white;width:100%">
<h3>Shopping cart</h3>
<div style="height:2.5cm;background-color:#8f8d8d;width:100%">Your cart is currently empty</div>
</div>
<div style="background-color:white;width:100%">
<h4>Popular products or banner</h4>
<p>Iphone 11 Pro Max</p>
<img src="11PM.jpg" style="width:50%">
<p>Iphone 12 Pro Max</p>
<img src="12PM.jpg" style="width:50%">
<p>Samsung Galaxy S20</p>
<img src="S20.jpg" style="width:50%">
</div>
</div>
</body>
</html>
Solution
In your servlet you are doing
context.setAttribute("p", p);
But in your JSP you are doing:
<c:out value="${s.id}"/>
Obviously, your names must match and the tag should be:
<c:out value="${p.id}"/>
One other thing I notice is that you are not dispatching to the JSP. You need to do a requestDispatcher.forward() to your JSP
Here is the minimum example to make everything work:
Servlet:
package connect;
import java.io.IOException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
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 products.Product;
@WebServlet("/Connector")
public class Connector extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
Product p = new Product();
p.setId(1234);
ServletContext context = getServletContext();
context.setAttribute("p", p);
RequestDispatcher requestDispatcher = request.getRequestDispatcher("/Home.jsp"); // <--- your path here
requestDispatcher.forward(request, response);
}
}
If your Home.jsp file is on some other path, change above accordingly.
Home.jsp:
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<c:out value="${p.id}" />
With that being said, a few comments on your controller code.
First of all, don't use @SuppressWarnings unless you know what you are doing. Based on your code, you are at a beginner level, so this annotation can hide a lot of issues that you should pay attention to.
You use an output stream PrintWriter out = response.getWriter(); in your code, but only to write a exception message into it when your code fails. If your code works, not only that you don't use your JSP, but you also don't use this out object to write a response to send to the client. So in regards with generating a response, your servlet did nothing, that's why nothing was displayed.
If you are doing a search for a product, you can write a WHERE clause and retrieve only what you are searching for instead of getting all the products in the database and then looping through them. Make sure you use prepared statement parameters when building your query. DO NOT CONCATENATE STRING TO BUILD YOUR SQL QUERY. That can cause SQL injection vulnerabilities.
You are looping through a list of product results but you are declaring your product object outside of the while loop. The result of this is that your array will only be filled with this reference object, that will point to objects that have the last retrieved value from the database. You need to move the product creation inside the while loop, like this:
while (rs.next()) {
Product p = new Product();
p.setId(rs.getInt("product_id"));
// all the other props
pro.add(p);
}
You are using the Product re; reference to search for your product, but then you never use it because you do a p=pro.get(0); to get the first product from your list and you use p to place in context for the JSP. I'me assuming you mean to use re instead.
Don't compare strings with ==. This code:
if (pro.get(i).getName() == name) {
should probably be something like:
if (pro.get(i).getName().equalsIgnoreCase(name)) {
Even more, you need to make sure you protect yourself from NullPointerExceptions in case getName() can also return null. If you used a WHERE SQL clause, you wouldn't need to loop again and search for products.
Finally, you should read some books or documentation on the concepts and code you are using. You might be able to put something together eventually, without fully understanding what's going on, but it might not necessarily be what you expect.
Answered By - Bogdan
