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You can use the SecurityContext and HttpServletRequest interfaces to authenticate users for a web application programmatically.

SecurityContext

HttpServletRequest

package test;

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

@WebServlet(name="TutorialServlet", urlPatterns={"/TutorialServlet"})
public class TutorialServlet extends HttpServlet {
    @EJB
    private ConverterBean converterBean;

    /**
     * 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");
        PrintWriter out = response.getWriter();
        try {

            out.println("<html>");
            out.println("<head>");
            out.println("<title>Servlet TutorialServlet</title>");
            out.println("</head>");
            out.println("<body>");
            request.login("TutorialUser", "TutorialUser");
            BigDecimal result =
                converterBean.dollarToYen(new BigDecimal("1.0"));
            out.println("<h1>Servlet TutorialServlet result of dollarToYen= "
                + result + "</h1>");
            out.println("</body>");
            out.println("</html>");
        } catch (Exception e) {
            throw new ServletException(e);
        } finally {
            request.logout();
            out.close();
        }
    }
}

package com.example.test;

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class TestServlet extends HttpServlet {

    protected void processRequest(HttpServletRequest request,
            HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        try {
            request.authenticate(response);
            out.println("Authenticate Successful");
        } finally {
            out.close();
        }
    }

In general, the container enforces security management in a manner that is transparent to the web component. Use the security APIs described in this section only in the less frequent situations in which the web component methods need to access the security context information.

The Java EE Security API specification defines the following methods of the SecurityContext interface that allow the application to test aspects of the caller data:

• getCallerPrincipal() retrieves the Principal representing the caller. This is the container-specific representation of the caller principal, and the type may differ from the type of the caller principal originally established by an HttpAuthenticationMechanism. This method returns null for an unauthenticated caller.

• getPrincipalsByType() retrieves all principals of the given type. This method can be used to retrieve an application-specific caller principal established during authentication. This method is primarily useful in the case that the container’s caller principal is a different type than the application caller principal, and the application needs specific information behavior available only from the application principal. This method returns an empty Set if the caller is unauthenticated, or if the requested type is not found.

  Where both a container caller principal and an application caller principal are present, the value returned by getName() is the same for both principals.

• isCallerInRole() takes a String argument that represents the role to be tested. The specification does not define how the role determination is made, but the result must be the same as if the corresponding container-specific call had been made (for example HttpServletRequest.isUserInRole(), EJBContext.isCallerInRole()), and must be consistent with the result implied by specifications that prescribe role-mapping behavior.

Servlet 4.0 specifies the following methods that enable you to access security information about the component’s caller.

• getRemoteUser determines the user name with which the client authenticated. The getRemoteUser method returns the name of the remote user (the caller) associated by the container with the request. If no user has been authenticated, this method returns null.

• isUserInRole determines whether a remote user is in a specific security role. If no user has been authenticated, this method returns false. This method expects a String user role-name parameter.

  The security-role-ref element should be declared in the deployment descriptor with a role-name subelement containing the role name to be passed to the method. Using security role references is discussed in Declaring and Linking Role References.

• getUserPrincipal determines the principal name of the current user and returns a java.security.Principal object. If no user has been authenticated, this method returns null. Calling the getName method on the Principal returned by getUserPrincipal returns the name of the remote user.

Your application can make business-logic decisions based on the information obtained using these APIs.

The SecurityContext interface, as specified in the Java EE Security API specification, defines the following method for programmatically testing access to a resource:

• hasAccessToWebResource() method determines if the caller has access to the specified web resource for the specified HTTP methods, as determined by the security constraints configured for the application.

  The resource parameter is an URLPatternSpec, as defined by the Java Authorization Contract for Containers 1.5 specification (http://jcp.org/en/jsr/detail?id=115), that identifies an application-specific web resource.

  This method can be used to check access to resources in the current application only — it cannot be called cross-application, or cross-container, to check access to resources in a different application.

For example, consider the following Servlet definition:

And the following call to hasAccessToWebResource():

The above hasAccessToWebResource() call returns true if, and only if, the caller is in role "foo".

The following code demonstrates the use of programmatic security for the purposes of programmatic login. This servlet does the following.

1. It displays information about the current user.

2. It prompts the user to log in.

3. It prints out the information again to demonstrate the effect of the login method.

4. It logs the user out.

5. It prints out the information again to demonstrate the effect of the logout method.

A security role reference is a mapping between the name of a role that is called from a web component using isUserInRole(String role) and the name of a security role that has been defined for the application. If no security-role-ref element is declared in a deployment descriptor and the isUserInRole method is called, the container defaults to checking the provided role name against the list of all security roles defined for the web application. Using the default method instead of using the security-role-ref element limits your flexibility to change role names in an application without also recompiling the servlet making the call.

The security-role-ref element is used when an application uses the HttpServletRequest.isUserInRole(String role). The value passed to the isUserInRole method is a String representing the role name of the user. The value of the role-name element must be the String used as the parameter to the HttpServletRequest.isUserInRole(String role). The role-link must contain the name of one of the security roles defined in the security-role elements. The container uses the mapping of security-role-ref to security-role when determining the return value of the call.

For example, to map the security role reference cust to the security role with role name bankCustomer, the elements would look like this:

If the servlet method is called by a user in the bankCustomer security role, isUserInRole("cust") returns true.

The role-link element in the security-role-ref element must match a role-name defined in the security-role element of the same web.xml deployment descriptor, as shown here:

A security role reference, including the name defined by the reference, is scoped to the component whose deployment descriptor contains the security-role-ref deployment descriptor element.