jaasclient.java

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import java.io.*;
import java.util.Iterator;
import java.security.PrivilegedAction;
import javax.security.auth.Subject;
import javax.security.auth.login.LoginContext;

public class JAASClient {
  public static void main(String [] args)  throws Exception{
    try {
      loginAndDoSomething();
    }
    catch (Exception e) {
   System.out.println(e);
/*
     BufferedWriter br = new BufferedWriter(
                  new OutputStreamWriter(new FileOutputStream("1.txt")));
     String s=e.toString();
    br.write(s,0,s.length());
*/
//      e.printStackTrace();
    }
  }
  public static void loginAndDoSomething() throws
                                        Exception {
    LoginContext ctx = new
                       LoginContext("SimpleLogin");
    ctx.login();
    Subject subj = ctx.getSubject();
    System.out.println("Login assigned these principals: ");
    Iterator it = subj.getPrincipals().iterator(); 
    while (it.hasNext()) 
        System.out.println("\t" + it.next());
    
    Subject.doAs(subj, new PrivilegedAction() {
        public Object run() {
          System.out.println("You live at " + 
                   System.getProperty("user.home"));
          return null;
        }
      });
    ctx.logout();
  }
}