Servlet crashes when logging in with a registered user, but not when logging in automatically after registering an account
Question
This is a college lab. I've been stuck for 3 days now. I'm building an image viewer website with Google App Engine and Java. I've made a web page with login functionality. On the welcome page the user can register an account or log in. If I register a new account there's no problem, the user data is saved, cookies are added to the http response and the user progresses to the next page where he/she can upload and view images in the category that they selected on registering an account. However, if I try to log in as a user that already has an account the app crashes after the successful login with a NullPointerException I cannot figure out what's wrong.
The process for registering and logging in is the same with the exception of saving to and reading from the database.
Here's my Welcome page:
<%@ page import="com.google.appengine.api.blobstore.BlobstoreServiceFactory" %>
<%@ page import="com.google.appengine.api.blobstore.BlobstoreService" %>
<%@ page import="com.blobtest.UserManager" %>
<%@ page import="com.blobtest.UserDatastore" %>
<%@ page import="com.google.appengine.api.datastore.Entity" %>
<%@ page import="java.util.List" %>
<%
BlobstoreService blobstoreService = BlobstoreServiceFactory.getBlobstoreService();
UserManager userManager = new UserManager();
UserDatastore dataStore = new UserDatastore();
Cookie cookie = null;
Cookie[] cookies = null;
cookies = request.getCookies();
if(cookies != null){
System.out.println("");
System.out.println("============ From WELCOME.JSP =================");
System.out.println("");
System.out.println("Found Cookies!!");
for(int i = 0; i < cookies.length; i++){
cookie = cookies[i];
System.out.println("");
System.out.println("Name: " + cookie.getName());
System.out.println("Value: " + cookie.getValue());
System.out.println("Domain: " + cookie.getDomain());
}
System.out.println("");
System.out.println("============ From WELCOME.JSP =================");
System.out.println("");
}
%>
<html>
<head>
<title>Welcome</title>
<link rel="StyleSheet" type="text/css" href="Style.css" />
</head>
<body>
<h1>Welcome to the Picture Gallery!</h1>
<p>To log in enter your email and password and press "Login", to register enter your email, the password you want and select a role from the menu and press "Login"</p>
<form action="usermanager" method="post">
<label>E-Mail:</label>
<input name="username" type="text" size="30" maxlength="2048" />
<label>Password:</label>
<input name="password" type="password" size="30" maxlength="2048" />
<label>Role:</label>
<select name="register_role">
<%
List<Entity> registerRoles = dataStore.getRoles();
for(Entity role : registerRoles){
out.println("<option>" + role.getProperty("role") + "</option>");
}
%>
</select>
<input type="submit" value="Login">
</form>
<h1>Gallery Viewer</h1>
<p>Select a gallery from the menu below and press "Go" to view it</p>
<form action="/serve" method="get">
<select name="role">
<%
List<Entity> roles = dataStore.getRoles();
for(Entity role : roles){
out.println("<option>" + role.getProperty("role") + "</option>");
}
%>
</select>
<input type="submit" value="Go">
</form>
</body>
</html>
Here's my UserManager class:
package com.blobtest;
import java.io.IOException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.google.appengine.api.datastore.Entity;
public class UserManager extends HttpServlet {
/**
*
*/
private static final long serialVersionUID = 8824378069546886214L;
public final String ROLE_SOLDIER = "soldier";
public final String ROLE_PROGRAMMER = "programmer";
public final String ROLE_SINGER = "singer";
public final String ROLE_FOOTBALLER = "footballer";
public final String COOKIE_PROPERTY_ROLE = "role";
public final String COOKIE_PROPERTY_USER = "verifieduser";
public final String COOKIE_APP_DOMAIN = "ImageViewer.se";
private UserDatastore datastore;
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
datastore = new UserDatastore();
checkCookies(request);
String email = request.getParameter("username");
String password = request.getParameter("password");
String role = request.getParameter("register_role");
Entity user = datastore.selectUser(email);
/*
* If the database returns a user, check the password matches, otherwise
* register the user
*/
if (user != null) {
if (password.equals(user.getProperty("password"))) {
message("REGISTERED USER FOUND:", true, 0);
message("user: " + user.getProperty("email") + "; Password: "
+ user.getProperty("password"), false, 0);
// request.getSession().setAttribute("loggedInUser", userName);
Cookie cookie = new Cookie(this.COOKIE_PROPERTY_ROLE, user
.getProperty("role").toString());
message("UserManager: New Cookie created with role: "
+ user.getProperty("role").toString(), false, 0);
cookie.setMaxAge(300); // -1 = persist for the duration of the
// session; 0 = remove cookie; value > 0
// = time in seconds.
response.addCookie(cookie);
Cookie userCookie = new Cookie(this.COOKIE_PROPERTY_USER, user
.getProperty("email").toString());
message("UserManager: New Cookie created with verifieduser: "
+ user.getProperty("email").toString(), true, 1);
userCookie.setMaxAge(300); // -1 = persist for the duration of
// the session; 0 = remove cookie;
// value > 0 = time in seconds.
response.addCookie(userCookie);
dispatch(request, response, "/loggedin.jsp");
} else {
message("Passwords don't match, invalidating session", true, 0);
message("", true, 1);
request.getSession().invalidate(); // need to dispose of cookies
// here, not currently using
// sessions
dispatch(request, response, "/welcome.jsp");
}
} else {
datastore.addUser(email, password, role);
message("NEW USER ADDED:", true, 0);
Cookie cookie = new Cookie(this.COOKIE_PROPERTY_ROLE, role);
message("UserManager: New Cookie created with role: " + role,
false, 0);
cookie.setMaxAge(300); // -1 = persist for the duration of the
// session; 0 = remove cookie; value > 0 =
// time in seconds.
response.addCookie(cookie);
Cookie userCookie = new Cookie(this.COOKIE_PROPERTY_USER, email);
message("UserManager: New Cookie created with verifieduser: "
+ email, true, 1);
userCookie.setMaxAge(300); // -1 = persist for the duration of the
// session; 0 = remove cookie; value > 0
// = time in seconds.
response.addCookie(userCookie);
dispatch(request, response, "/register.jsp");
}
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException {
}
protected void dispatch(HttpServletRequest request,
HttpServletResponse response, String page)
throws javax.servlet.ServletException, java.io.IOException {
RequestDispatcher dispatcher = getServletContext()
.getRequestDispatcher(page);
dispatcher.forward(request, response);
}
private void checkCookies(HttpServletRequest request) {
Cookie cookie = null;
Cookie[] cookies = null;
cookies = request.getCookies();
if (cookies != null) {
message("Found Cookies!!", true, 0);
for (int i = 0; i < cookies.length; i++) {
cookie = cookies[i];
message("Name: " + cookie.getName(), false, 0);
message("Value: " + cookie.getValue(), false, 0);
message("Domain: " + cookie.getDomain(), false, 0);
}
message("", true, 1);
}
}
/**
* Formats the message and message wrapper
*
* @param message
* The message to print
* @param includeWrapper
* true to include header/footer labels
* @param position
* if includeWrapper is true, then set 0 for header 1 for footer,
* otherwise set 0.
*/
private void message(String message, boolean includeWrapper, int position) {
if (includeWrapper) {
if (position == 0) {
System.out.println("");
System.out
.println("==========From USERMANAGER===================");
System.out.println("");
System.out.println(message);
} else {
System.out.println(message);
System.out.println("");
System.out
.println("========== From USERMANAGER ===================");
System.out.println("");
}
} else {
System.out.println(message);
}
}
}
My "Login Successful" and "Registration Successful" pages are exactly the same, they simply redirect to the Uploader.jsp page below:
<%@ page import="com.google.appengine.api.blobstore.BlobstoreServiceFactory" %>
<%@ page import="com.google.appengine.api.blobstore.BlobstoreService" %>
<%@ page import="com.blobtest.UserManager" %>
<%@ page import="com.blobtest.UserDatastore" %>
<%@ page import="com.google.appengine.api.datastore.Entity" %>
<%@ page import="java.util.List" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<% //taglib xmlns:h="http://java.sun.com/jsf/html"prefix="h" %>
<%
BlobstoreService blobstoreService = BlobstoreServiceFactory.getBlobstoreService();
UserManager userManager = new UserManager();
UserDatastore dataStore = new UserDatastore();
Cookie[] cookies = request.getCookies();
Cookie userCookie = null;
boolean ok = false;
for(int i = 0; i < cookies.length; i++){
if(cookies[i].getName().equals(userManager.COOKIE_PROPERTY_USER)){
if(cookies[i].getValue() != null){
ok = true;
}
}else if(cookies[i].getName().equals(userManager.COOKIE_PROPERTY_ROLE)){
userCookie = cookies[i];
}
}
if(!ok){
System.out.println("Request failed, number of cookies found: " + cookies.length + ", redirecting to welcome.jsp");
for(int i = 0; i < cookies.length; i++){
System.out.println("Name: " + cookies[i].getName() + ", Value: " + cookies[i].getValue());
}
RequestDispatcher dispatcher = getServletContext()
.getRequestDispatcher("/welcome.jsp");
dispatcher.forward(request, response);
}
%>
<html>
<head>
<title>Upload Test</title>
<link rel="StyleSheet" type="text/css" href="style.css" />
</head>
<body>
<form action="<%= blobstoreService.createUploadUrl("/upload") %>" method="post" enctype="multipart/form-data">
<input type="text" name="description">
<input type="file" name="myFile">
<input type="submit" value="Submit">
</form>
<form action="/usermanager" method="post" enctype="multipart/form-data">
</form>
<form action="/serve" method="get">
<select name="role">
<%
if(userCookie != null) out.println("<option>" + userCookie.getValue() + "</option>");
%>
</select>
<input type="submit" value="Go">
</form>
<%
Cookie cookie2 = null;
Cookie[] cookies2 = null;
// Get an array of Cookies associated with this domain
cookies2 = request.getCookies();
if( cookies2 != null ){
out.println("<h2> Found Cookies Name and Value</h2>");
for (int i = 0; i < cookies.length; i++){
cookie2 = cookies2[i];
out.print("Name : " + cookie2.getName( ) + ", ");
out.print("Value: " + cookie2.getValue( )+" <br/>");
}
}else{
out.println("<h2>No cookies founds</h2>");
}
%>
<a href="/logout.jsp">Click to Log Out</a>
</body>
</html>
The page above is where the application crashes. If I try to log in with a previously registered user I get the following error (Some printouts from the UserManager Included):
Retreiving user: paul@email.com, 1234, programmer
==========From USERMANAGER===================
REGISTERED USER FOUND:
user: paul@email.com; Password: 1234
UserManager: New Cookie created with role: programmer
UserManager: New Cookie created with verifieduser: paul@email.com
========== From USERMANAGER ===================
mar 30, 2014 12:53:53 EM com.google.apphosting.utils.jetty.JettyLogger warn
WARNING: /uploader.jsp
java.lang.NullPointerException
at org.apache.jsp.uploader_jsp._jspService(uploader_jsp.java:76)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:377)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
at com.google.appengine.tools.development.PrivilegedJspServlet.access$101(PrivilegedJspServlet.java:23)
at com.google.appengine.tools.development.PrivilegedJspServlet$2.run(PrivilegedJspServlet.java:61)
at java.security.AccessController.doPrivileged(Native Method)
at com.google.appengine.tools.development.PrivilegedJspServlet.service(PrivilegedJspServlet.java:58)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
at com.google.appengine.api.socket.dev.DevSocketFilter.doFilter(DevSocketFilter.java:74)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.ResponseRewriterFilter.doFilter(ResponseRewriterFilter.java:127)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.HeaderVerificationFilter.doFilter(HeaderVerificationFilter.java:34)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:63)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.StaticFileFilter.doFilter(StaticFileFilter.java:125)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.DevAppServerModulesFilter.doDirectRequest(DevAppServerModulesFilter.java:366)
at com.google.appengine.tools.development.DevAppServerModulesFilter.doDirectModuleRequest(DevAppServerModulesFilter.java:349)
at com.google.appengine.tools.development.DevAppServerModulesFilter.doFilter(DevAppServerModulesFilter.java:116)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
at com.google.appengine.tools.development.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:98)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:487)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:547)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)
==========From USERMANAGER===================
NEW USER ADDED:
UserManager: New Cookie created with role: soldier
UserManager: New Cookie created with verifieduser: paul3@email.com
========== From USERMANAGER ===================
mar 30, 2014 12:54:32 EM com.google.appengine.api.datastore.dev.LocalDatastoreService$PersistDatastore persist
INFO: Time to persist datastore: 56 ms
As you can see above, when adding a new user I don't get any error, it proceeds to the uploader.jsp page as it should and I can upload and view pictures without any problems. Any pointers would be greatly appreciated.
1 answers
solution1
1 ACCPTED 2014-03-31 04:49:17
check cokkies may be null in bottom of your jsp for (int i = 0; i < cookies.length; i++){ line of code:
<%
Cookie cookie2 = null;
Cookie[] cookies2 = null;
// Get an array of Cookies associated with this domain
cookies2 = request.getCookies();
if( cookies2 != null ){
out.println("<h2> Found Cookies Name and Value</h2>");
for (int i = 0; i < cookies.length; i++){ //Here cookies may be null
cookie2 = cookies2[i];
out.print("Name : " + cookie2.getName( ) + ", ");
out.print("Value: " + cookie2.getValue( )+" <br/>");
}
}else{
out.println("<h2>No cookies founds</h2>");
}
%>
this answer may help you for how to use/retrive cokkies in jsp using jstl, you can avoid some NullPointerException in this way.
see also:
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