Hyperlink `` not invoking a mapped Servlet. Returning 404: Resource not found

Question

What it says on the title. I'm trying to invoke a servlet to create a page when I click on a link. Attached below is the code.

HTML:

<html>
<head>
    <title>NavBar</title>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="sheet.css">
</head>
<body>        
    <section class="ft_root">
        <div class="ft">
            <ul>
                <li><a href="/entry/test.html"> 1 </a></li>
                <li><a href="#"> 2 </a></li>
                <li><a href="#"> 3 </a></li>
                <li><a href="#"> 4 </a></li>
                <li><a href="#"> 5 </a></li>

            </ul>

        </div>

</html>

Web.XML

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
 version="3.1">
    <session-config>
        <session-timeout>
            30
        </session-timeout>
    </session-config>
    <servlet>
        <servlet-name>entry_page_gen</servlet-name>
        <servlet-class>Servlets.entry_page_gen</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>entry_page_gen</servlet-name>
        <url-pattern>/entry/*</url-pattern>
    </servlet-mapping>       
</web-app>

entry_page_gen.java

package Servlets;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 *
 * @author oras
 */
@WebServlet(name = "entry_page_gen", urlPatterns = {"/entry/*"})
public class entry_page_gen 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");
        try (PrintWriter out = response.getWriter()) {
            /* TODO output your page here. You may use following sample code. */
            out.println("<!DOCTYPE html>");
            out.println("<html>");
            out.println("<head>");
            out.println("<title>Servlet entry_page_gen</title>");            
            out.println("</head>");
            out.println("<body>");
            out.println("<h1>Servlet entry_page_gen at " + request.getContextPath() +     "</h1>");
            out.println("</body>");
            out.println("</html>");
        }
    }

    // <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 {
        processRequest(request, response);
    }

    /**
     * Handles the HTTP <code>POST</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 doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    /**
     * Returns a short description of the servlet.
     *
     * @return a String containing servlet description
     */
    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>

}

entry_page_gen.java is stored in a package called Servlets.

What's going wrong? If more information is needed, please ask. I didn't want to bog down the question with info that might not be needed.

A point to note is that if I change the Web.xml -> <servlet-mapping> -> <url-pattern> to /entry_page_gen and call the servlet from a <form> with the action parameter, everything works fine.

P.S: I referred to this question while creating the above pieces of code.

So, you want to display the content of your HTML file instead of the content created in the servlet, right? — sirandy, Nov 24 '20 at 20:19
Is your web app deployed as a ROOT application of your servlet container? — Gabriel Belingueres, Nov 24 '20 at 20:43

score 0 · Answer 1 · answered Nov 24 '20 at 20:29

Well here is a solution for you.

entry_page_gen.java (By the way you should change this name to follow the java convention)

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    //processRequest(request, response);
     response.sendRedirect("hello.html");
     return;
}

Configuration:

Output:

Notes:

In the image you are seeing the URL http://localhost:8080/web-project/hello.html because of the redirect in the method, but you can reach this element with: http://localhost:8080/web-project/entry

The explanation of the configuration could see here: https://stackoverflow.com/a/26329628/1670134

score 0 · Answer 2 · answered Nov 24 '20 at 20:57

As answered in here, the initial slash character refers to the path from the base URL (by default the domain name, unless changed with a <base> HTML element). So if your app URL is http://www.example.com/myapp, then an anchor <a href="/entry/test.html"> 1 </a> will refer to http://www.example.com/entry/test.html, therefore the servlet is not called.

You could change the anchor's href to this <a href="/myapp/entry/test.html"> 1 </a>

Hyperlink `` not invoking a mapped Servlet. Returning 404: Resource not found

2 Answers2