Issue
I'm working on a simple login servlet in which the user enters his email and password which are stored in a text file(I can't use a database) ,if the credentials are correct then the user will be redirected to a weclome jsp page if not correct then to a fail login jsp page , the problem that I'm facing is that I'm always getting redirected to the login fail page even though I'm checking if the email and password are in the text file and are correct
I'm using Tomcat 10
So the text file looks like this :
- [email protected],awesome100
- [email protected],cool009
the email and password are seperated by a ','
Here's the Code :
package com.example.try8;
import java.io.*;
import java.security.Principal;
import java.util.HashMap;
import java.util.Map;
import jakarta.servlet.ServletConfig;
import jakarta.servlet.ServletContext;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
@WebServlet("/HelloServlet")
public class HelloServlet extends HttpServlet {
/**
*
*/
private static final long serialVersionUID = -5498866193863633001L;
/**
* HashMap to store all users credentials
*/
private final Map<String, String> credentialsPairs = new HashMap<>
();
@Override
public void init(ServletConfig config) throws ServletException {
String delimiter = ",";
String line = "";
/**
* Credentials file will be there in WEB-INF directory as it
provide secured
* access only.
*/
String credentialFile = "/WEB-INF/accounts.txt";
/**
* Read the file and prepare Map with username as key and
password as value We
* have put this code in init method as it is called once only
that will avoid
* overhead of iterating values from file for each request
*/
InputStream is = null;
InputStreamReader isr = null;
BufferedReader br = null;
ServletContext context = config.getServletContext();
try {
/**
* Open stream of file
*/
is = context.getResourceAsStream(credentialFile);
if (is != null) {
/**
* Read the file line by line and store email as a key
and password as value
*/
isr = new InputStreamReader(is);
br = new BufferedReader(isr);
while ((line = br.readLine()) != null) {
String[] credentials = line.split(delimiter);
// credentials[0] is email and credentials[1] is
password
credentialsPairs.put(credentials[0],
credentials[1]);
}
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (br != null) {
br.close();
}
if (isr != null) {
isr.close();
}
if (is != null) {
is.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
public void doGet(HttpServletRequest request, HttpServletResponse
response) throws IOException {
/**
* Get user entered credentials
*/
String userEmail = request.getParameter("email");
String userPassword = request.getParameter("password");
PrintWriter out = response.getWriter();
boolean isValidUser = false;
/**
* Get value from Map for user entered email address.
*/
String password = credentialsPairs.get(userEmail);
/**
* If User with entered email address found then we will get
password for that
* user
*/
if (password != null) {
/**
* Compare password entered by user with one that is
retrieved from file
*/
if (password.equals(userPassword)) {
isValidUser = true;
} else {
// Please enter correct password
out.println("Please enter correct password");
}
} else {
// User does not exists
out.println("User does not exist");
}
if (isValidUser) {
response.sendRedirect("welcome.jsp");
} else {
response.sendRedirect("fail.jsp");
}
}
public void destroy() {
/**
* Free up the map
*/
credentialsPairs.clear();
}
}
The index.jsp :
<%@ page contentType="text/html; charset=UTF-8" pageEncoding="UTF-
8" %>
<!DOCTYPE html>
<html>
<head>
<title>JSP - Hello World</title>
</head>
<body>
<div align="center">
<h1>
Sign-In
</h1>
<form action="login" method="get">
<table>
<tr> <td>E-mail : <input type="email" name="email"></td>
</tr>
<tr> <td>Password : <input type="password" name="password">
</td></tr>
<tr> <td><input type="submit" value="Login"></td></tr>
</table>
</form>
</div>
</body>
</html>
The web.xml :
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="https://jakarta.ee/xml/ns/jakartaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="https://jakarta.ee/xml/ns/jakartaee
https://jakarta.ee/xml/ns/jakartaee/web-app_5_0.xsd"
version="5.0">
<servlet>
<servlet-name>lgn</servlet-name>
<servlet-class>com.example.try8.HelloServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>lgn</servlet-name>
<url-pattern>/login</url-pattern>
</servlet-mapping>
</web-app>
Solution
Hello @Mohammed Hamdoon
You can find below code. That serves your objective and eliminate costly over head of iterating over file each time to match email and password. Here I can login successfully with the credentials given in accounts.txt file.
Please read my comments in servlet file for further explanations.
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Map;
import jakarta.servlet.ServletConfig;
import jakarta.servlet.ServletContext;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
@WebServlet("/HelloServlet")
public class HelloServlet extends HttpServlet {
/**
*
*/
private static final long serialVersionUID = -5498866193863633001L;
/**
* HashMap to store all users credentials
*/
private final Map<String, String> credentialsPairs = new HashMap<>();
@Override
public void init(ServletConfig config) throws ServletException {
String delimiter = ",";
String line = "";
/**
* Credentials file will be there in WEB-INF directory as it provide secured
* access only.
*/
String credentialFile = "/WEB-INF/accounts.txt";
/**
* Read the file and prepare Map with username as key and password as value We
* have put this code in init method as it is called once only that will avoid
* overhead of iterating values from file for each request
*/
InputStream is = null;
InputStreamReader isr = null;
BufferedReader br = null;
ServletContext context = config.getServletContext();
try {
/**
* Open stream of file
*/
is = context.getResourceAsStream(credentialFile);
if (is != null) {
/**
* Read the file line by line and store email as a key and password as value
*/
isr = new InputStreamReader(is);
br = new BufferedReader(isr);
while ((line = br.readLine()) != null) {
String[] credentials = line.split(delimiter);
// credentials[0] is email and credentials[1] is password
credentialsPairs.put(credentials[0], credentials[1]);
}
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (br != null) {
br.close();
}
if (isr != null) {
isr.close();
}
if (is != null) {
is.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
/**
* Get user entered credentials
*/
String userEmail = request.getParameter("email");
String userPassword = request.getParameter("password");
boolean isValidUser = false;
/**
* Get value from Map for user entered email address.
*/
String password = credentialsPairs.get(userEmail);
/**
* If User with entered email address found then we will get password for that
* user
*/
if (password != null) {
/**
* Compare password entered by user with one that is retrieved from file
*/
if (password.equals(userPassword)) {
isValidUser = true;
} else {
// Please enter correct password
}
} else {
// User does not exists
}
if (isValidUser) {
response.sendRedirect("welcome.jsp");
} else {
response.sendRedirect("fail.jsp");
}
}
public void destroy() {
/**
* Free up the map
*/
credentialsPairs.clear();
}
}
Please share your comments, if you have any question on above.
Answered By - kody-technolab
