在 servlet 中读取电子邮件和密码 (Java EE)

Question

我正在开发一个简单的登录 servlet，用户在其中输入存储在文本文件中的电子邮件和密码（我不能使用数据库），如果凭据正确，则用户将重定向到 weclome jsp 页面如果不正确然后登录失败 jsp 页面，我面临的问题是我总是被重定向到登录失败页面，即使我是检查电子邮件和密码是否在文本文件中并且正确

我正在使用 Tomcat 10

因此文本文件如下所示：

example1@gmail.com,awesome100
example2@hotmail.hotmail.com,cool009

邮箱和密码用','分隔

代码如下：

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();
}
}

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>

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>

Answer 1

你好@Mohammed Hamdoon

您可以找到以下代码。这为您的 objective 服务并消除了每次迭代文件以匹配电子邮件和密码的昂贵开销。在这里，我可以使用 accounts.txt 文件中提供的凭据成功登录。

请阅读我在 servlet 文件中的注释以获得进一步的解释。

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();
    }
}

如果您对以上内容有任何疑问，请发表您的意见。

在 servlet 中读取电子邮件和密码 (Java EE)

reading email and password in servlet (Java EE)

java

servlets

java-ee-8