Chapter 4. Creating a web application

Create a web application containing a servlet that returns the user name obtained from the logged-in user’s principal and attributes. If there is no logged-in user, the servlet returns the text "NO AUTHENTICATED USER".

Prerequisites

  • You have created a Maven project.
  • JBoss EAP is running.

Procedure

  1. Create a directory to store the Java files.

    Syntax

    $ mkdir -p src/main/java/<path_based_on_artifactID>

    Example

    $ mkdir -p src/main/java/com/example/app

  2. Navigate to the new directory.

    Syntax

    $ cd src/main/java/<path_based_on_artifactID>

    Example

    $ cd src/main/java/com/example/app

  3. Create a file SecuredServlet.java with the following content: 

    package com.example.app;

import java.io.IOException;
import java.io.PrintWriter;
import java.security.Principal;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Set;

import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.wildfly.security.auth.server.SecurityDomain;
import org.wildfly.security.auth.server.SecurityIdentity;
import org.wildfly.security.authz.Attributes;
import org.wildfly.security.authz.Attributes.Entry;
/**
 * A simple secured HTTP servlet. It returns the user name and
 * attributes obtained from the logged-in user's Principal. If
 * there is no logged-in user, it returns the text
 * "NO AUTHENTICATED USER".
 */

@WebServlet("/secured")
public class SecuredServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        try (PrintWriter writer = resp.getWriter()) {

        	Principal user = req.getUserPrincipal();
        	SecurityIdentity identity = SecurityDomain.getCurrent().getCurrentSecurityIdentity();
        	Attributes identityAttributes = identity.getAttributes();
        	Set <String> keys = identityAttributes.keySet();
        	String attributes = "<ul>";

        	for (String attr : keys) {
        		attributes += "<li> " +  attr + " : " + identityAttributes.get(attr).toString() + "</li>";
        	}

        	attributes+="</ul>";
        	writer.println("<html>");
        	writer.println("  <head><title>Secured Servlet</title></head>");
        	writer.println("  <body>");
        	writer.println("    <h1>Secured Servlet</h1>");
        	writer.println("    <p>");
        	writer.print(" Current Principal '");
        	writer.print(user != null ? user.getName() : "NO AUTHENTICATED USER");
        	writer.print("'");
        	writer.print(user != null ? "\n" + attributes : "");
        	writer.println("    </p>");
        	writer.println("  </body>");
        	writer.println("</html>");
        }
    }

}

  4. In the application root directory, compile your application with the following command: 

    $ mvn package
...
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.015 s
[INFO] Finished at: 2022-04-28T17:48:53+05:30
[INFO] ------------------------------------------------------------------------

  5. Deploy the application. 

    $ mvn wildfly:deploy

Verification

You can now secure this application by using a security domain so that only authenticated users can access it.