Java实现登录与注册页面

下面是Java实现登录和注册页面的具体攻略：

1. 准备工作：

下载并安装Java JDK，安装JDK后需要配置一下环境变量，确保能在控制台中使用javac和java命令。
安装Java IDE，如Eclipse、IntelliJ IDEA等。

2. 实现注册页面

（1）创建Java web项目

打开IDE，点击File -> New -> Dynamic Web Project
设置项目名称和保存路径，并选择Target runtime为你的Tomcat版本
点击Finish，生成项目骨架

示例1：

<!-- 配置web.xml -->
<web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0">

  <servlet>
    <servlet-name>RegisterServlet</servlet-name>
    <servlet-class>com.example.web.RegisterServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>RegisterServlet</servlet-name>
    <url-pattern>/register</url-pattern>
  </servlet-mapping>

  <welcome-file-list>
    <welcome-file>register.jsp</welcome-file>
  </welcome-file-list>

</web-app>

<!-- register.jsp -->
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>注册页面</title>
</head>
<body>
  <form action="${pageContext.request.contextPath}/register" method="post">
    <table>
      <tr>
        <td>用户名</td>
        <td><input type="text" name="username"></td>
      </tr>
      <tr>
        <td>密码</td>
        <td><input type="password" name="password"></td>
      </tr>
      <tr>
        <td colspan="2">
          <input type="submit" value="注册">
          <input type="reset" value="重置">
        </td>
      </tr>
    </table>
  </form>
</body>
</html>

（2）创建Servlet类

在Java项目的src目录下创建一个Servlet类
在doPost()方法中获取request对象的参数，从而得到用户输入的用户名和密码
将用户名和密码插入到数据库中

示例2：

package com.example.web;

import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class RegisterServlet extends HttpServlet {

  private static final long serialVersionUID = 1L;

  private static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
  private static final String DB_URL = "jdbc:mysql://localhost:3306/test";
  private static final String USER = "root";
  private static final String PASSWORD = "root";

  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    String username = request.getParameter("username");
    String password = request.getParameter("password");

    Connection conn = null;
    PreparedStatement pstmt = null;

    try {
      Class.forName(JDBC_DRIVER);
      conn = DriverManager.getConnection(DB_URL, USER, PASSWORD);
      String sql = "INSERT INTO user (username, password) VALUES (?, ?)";
      pstmt = conn.prepareStatement(sql);
      pstmt.setString(1, username);
      pstmt.setString(2, password);
      pstmt.executeUpdate();
    } catch (SQLException se) {
      se.printStackTrace();
    } catch (Exception e) {
      e.printStackTrace();
    } finally {
      try {
        if (pstmt != null)
          pstmt.close();
      } catch (SQLException se2) {
      }
      try {
        if (conn != null)
          conn.close();
      } catch (SQLException se) {
        se.printStackTrace();
      }
    }

    response.sendRedirect("login.jsp");
  }

}

3. 实现登录页面

（1）创建登录页面

（2）创建Servlet类

示例3：

<!-- 配置web.xml -->
<web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0">

  <servlet>
    <servlet-name>LoginServlet</servlet-name>
    <servlet-class>com.example.web.LoginServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>LoginServlet</servlet-name>
    <url-pattern>/login</url-pattern>
  </servlet-mapping>

  <welcome-file-list>
    <welcome-file>login.jsp</welcome-file>
  </welcome-file-list>

</web-app>

<!-- login.jsp -->
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>登录页面</title>
</head>
<body>
  <form action="${pageContext.request.contextPath}/login" method="post">
    <table>
      <tr>
        <td>用户名</td>
        <td><input type="text" name="username"></td>
      </tr>
      <tr>
        <td>密码</td>
        <td><input type="password" name="password"></td>
      </tr>
      <tr>
        <td colspan="2">
          <input type="submit" value="登录">
          <input type="reset" value="重置">
        </td>
      </tr>
    </table>
  </form>
</body>
</html>

<!-- LoginServlet -->
public class LoginServlet extends HttpServlet {

  private static final long serialVersionUID = 1L;

  private static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
  private static final String DB_URL = "jdbc:mysql://localhost:3306/test";
  private static final String USER = "root";
  private static final String PASSWORD = "root";

  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    String username = request.getParameter("username");
    String password = request.getParameter("password");

    Connection conn = null;
    PreparedStatement pstmt = null;
    ResultSet rs = null;

    try {
      Class.forName(JDBC_DRIVER);
      conn = DriverManager.getConnection(DB_URL, USER, PASSWORD);
      String sql = "SELECT * FROM user WHERE username=? AND password=?";
      pstmt = conn.prepareStatement(sql);
      pstmt.setString(1, username);
      pstmt.setString(2, password);
      rs = pstmt.executeQuery();
      if (rs.next()) {
        request.getSession().setAttribute("username", username);
        response.sendRedirect("home.jsp");
      } else {
        response.sendRedirect("login.jsp");
      }
    } catch (SQLException se) {
      se.printStackTrace();
    } catch (Exception e) {
      e.printStackTrace();
    } finally {
      try {
        if (rs != null)
          rs.close();
      } catch (SQLException se2) {
      }
      try {
        if (pstmt != null)
          pstmt.close();
      } catch (SQLException se2) {
      }
      try {
        if (conn != null)
          conn.close();
      } catch (SQLException se) {
        se.printStackTrace();
      }
    }

  }

}

总结：

以上是Java实现登录与注册页面的完整攻略，需要注意的是，这些示例只是展示了如何在Java中实现登录和注册页面，并不包含完善的表单验证和数据类型校验等内容，需要在实际开发中根据需求进行相应的扩展。

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Java实现登录与注册页面

1. 准备工作：

2. 实现注册页面

3. 实现登录页面

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