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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>
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    Example

    $ mkdir -p src/main/java/com/example/app
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  2. Navigate to the new directory.

    Syntax

    $ cd src/main/java/<path_based_on_artifactID>
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    Example

    $ cd src/main/java/com/example/app
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  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>");
            }
        }
    
    }
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  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] ------------------------------------------------------------------------
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  5. Deploy the application.

    $ mvn wildfly:deploy
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Verification

  • In a browser, navigate to http://localhost:8080/simple-webapp-example/secured.

    You get the following message:

    Secured Servlet
    Current Principal 'NO AUTHENTICATED USER'
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    Because no authentication mechanism is added, you can access the application.

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

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