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Programmatic security is used by security-aware applications when declarative security alone is not sufficient to express the security model of the application.

Authenticating Users Programmatically

Servlet 3.0 specifies the following methods of the HttpServletRequest interface that enable you to authenticate users for a web application programmatically:

authenticate, which allows an application to instigate authentication of the request caller by the container from within an unconstrained request context. A login dialog box displays and collects the user name and password for authentication purposes.
login, which allows an application to collect user name and password information as an alternative to specifying form-based authentication in an application deployment descriptor.
logout, which allows an application to reset the caller identity of a request.

The following example code shows how to use the login and logout methods:

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();
        }
    }
}

The following example code shows how to use the authenticate method:

package com.sam.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();
        }
    }

Checking Caller Identity Programmatically

In general, security management should be enforced by the container in a manner that is transparent to the web component. The security API described in this section should be used only in the less frequent situations in which the web component methods need to access the security context information.

Servlet 3.0 specifies the following methods that enable you to access security information about the component’s caller:

getRemoteUser, which 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, which 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, which 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.

Example Code for Programmatic Security

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

It displays information about the current user.
It prompts the user to log in.
It prints out the information again to demonstrate the effect of the login method.
It logs the user out.
It prints out the information again to demonstrate the effect of the logout method.

package enterprise.programmatic_login;

import java.io.*;
import java.net.*;
import javax.annotation.security.DeclareRoles;
import javax.servlet.*;
import javax.servlet.http.*;

@DeclareRoles("javaee6user")
public class LoginServlet extends HttpServlet {

    /** 
     * Processes requests for both HTTP GET and POST methods.
     * @param request servlet request
     * @param response servlet response
     */
    protected void processRequest(HttpServletRequest request, 
                 HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        try {
            String userName = request.getParameter("txtUserName");
            String password = request.getParameter("txtPassword");
            
            out.println("Before Login" + "<br><br>");
            out.println("IsUserInRole?.." 
                        + request.isUserInRole("javaee6user")+"<br>");
            out.println("getRemoteUser?.." + request.getRemoteUser()+"<br>");
            out.println("getUserPrincipal?.." 
                        + request.getUserPrincipal()+"<br>");
            out.println("getAuthType?.." + request.getAuthType()+"<br><br>");
            
            try {
                request.login(userName, password); 
            } catch(ServletException ex) {
                out.println("Login Failed with a ServletException.." 
                    + ex.getMessage());
                return;
            }
            out.println("After Login..."+"<br><br>");
            out.println("IsUserInRole?.." 
                        + request.isUserInRole("javaee6user")+"<br>");
            out.println("getRemoteUser?.." + request.getRemoteUser()+"<br>");
            out.println("getUserPrincipal?.." 
                        + request.getUserPrincipal()+"<br>");
            out.println("getAuthType?.." + request.getAuthType()+"<br><br>");
            
            request.logout();
            out.println("After Logout..."+"<br><br>");
            out.println("IsUserInRole?.." 
                        + request.isUserInRole("javaee6user")+"<br>");
            out.println("getRemoteUser?.." + request.getRemoteUser()+"<br>");
            out.println("getUserPrincipal?.."
                        + request.getUserPrincipal()+"<br>");
            out.println("getAuthType?.." + request.getAuthType()+"<br>");
        } finally {
            out.close();
        }
    }
    ...
}

Declaring and Linking Role References

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 syntax would be:

<servlet>
...
    <security-role-ref>
        <role-name>cust</role-name>
        <role-link>bankCustomer</role-link>
    </security-role-ref>
...
</servlet>

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:

<security-role>
    <role-name>bankCustomer</role-name>
</security-role>

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.

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