Servlet程序访问的流程

2021-09-19 21:46:21

方式一:
jsp:
<font color="red">${ msg }</font>
<form action="/personal/requestLogin" method="post">
姓名:<input type="text" name="username"/><br/>
密码:<input type="password" name="password"/><br/>
<input type="submit" value="登录"/>
</form>

web.xml

<servlet>
<servlet-name>requestLogin</servlet-name>
<servlet-class>com.pers.request.service.LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>requestLogin</servlet-name>
<url-pattern>/requestLogin</url-pattern>
</servlet-mapping>

LoginServlet.java
public class LoginServlet extends HttpServlet {
// 登录校验代码
}

方式二:注解 (前提是@WebServlet("/LoginServlet")必须和类名LoginServlet一致)
jsp:
<font color="red">${ msg }</font>
<form action="/personal/LoginServlet" method="post">
姓名:<input type="text" name="username"/><br/>
密码:<input type="password" name="password"/><br/>
<input type="submit" value="登录"/>
</form>
LoginServlet.java
@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
// 登录校验代码
}

以下是详细代码:

==================================================傲娇的分割线==================================================

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<title>登录测试</title>

</head>

<body>

    <h3>登录页面</h3>

    <form action="/personal/requestLogin" method="post">

        姓名:<input type="text" name="username"/><br/>

        密码:<input type="password" name="password"/><br/>

        <input type="submit" value="登录"/>

    </form>

</body>

</html>

web.xml

<?xml version="1.0" encoding="UTF-8"?>

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

  <display-name>personal</display-name>

  <welcome-file-list>

    <welcome-file>index.html</welcome-file>

    <welcome-file>index.htm</welcome-file>

    <welcome-file>index.jsp</welcome-file>

    <welcome-file>default.html</welcome-file>

    <welcome-file>default.htm</welcome-file>

    <welcome-file>default.jsp</welcome-file>

  </welcome-file-list>

  <servlet>

    <servlet-name>requestLogin</servlet-name>

    <servlet-class>com.pers.request.service.LoginServlet</servlet-class>

  </servlet>

  <servlet-mapping>

    <servlet-name>requestLogin</servlet-name>

    <url-pattern>/requestLogin</url-pattern>

  </servlet-mapping>

</web-app>

LoginServlet.java

package com.pers.request.service;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.pers.request.domain.User;

/**

 * Servlet implementation class RequestLogin

 *

 * 登录测试

 */

//@WebServlet("/LoginServlet")

public class LoginServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    /**

     * @see HttpServlet#HttpServlet()

     */

    public LoginServlet() {

        super();

        // TODO Auto-generated constructor stub

    }

    /**

     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)

     */

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

        // 获取从前台表单传过来的值

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

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

        // 从数据库中查询

        UserService userService = new UserService();

        User user = userService.login(username, password);

        // 获取项目名称

        String projectName = request.getContextPath();

        // 判断user是否存在

        if (user!=null) {

            // 登录成功,跳转到登录成功页面(重定向)

            // (重定向的地址的写法：包含项目名称的，包含项目名称的，包含项目名称的，包含项目名称的)

            response.sendRedirect(projectName + "/jsp/request/success.jsp");

        } else {

            // 登录失败,提示信息并跳转到登录页面(转发)

            request.setAttribute("msg", "用户名或密码错误,请重新输入!");

            request.getRequestDispatcher("/jsp/request/login.jsp").forward(request, response);

        }

    }

    /**

     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)

     */

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

        // TODO Auto-generated method stub

        doGet(request, response);

    }

}

UserService.java

package com.pers.request.service;

import java.sql.Connection;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;

import com.pers.jdbc.utils.JdbcUtils;

import com.pers.request.domain.User;

/**

* @author liangyadong

* @date 2016年10月25日 下午4:16:00

* @version 1.0

*/

public class UserService {

    /**

     * 根据用户名和密码查询

     * @param username

     * @param password

     * @return

     */

    public User login(String username, String password){

        /**

         * 步骤

         * 1.加载驱动获取连接

         * 2.编写sql

         * 3.预编译sql

         * 4.设置参数

         * 5.执行sql

         * 6.遍历结果集,判断用户是否存在

         */

        Connection conn = null;

        PreparedStatement stmt = null;

        ResultSet rs = null;

        // 获取连接

        conn = JdbcUtils.getConnection();

        // 编写sql

        String sql = "select * from t_user where username = ? and password = ?";

        try {

            // 预编译sql

            stmt = conn.prepareStatement(sql);

            // 设置参数

            stmt.setString(1,username);

            stmt.setString(2, password);

            // 执行sql

            rs = stmt.executeQuery();

            // 遍历结果集

            while (rs.next()) {

                User user = new User();

                user.setUsername(rs.getString("username"));

                user.setPassword(rs.getString("password"));

                return user;

            }

        } catch (SQLException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        } finally {

            JdbcUtils.release(conn, stmt, rs);

        }

        return null;

    }

}

User.java

package com.pers.request.domain;

/**

* @author liangyadong

* @date 2016年10月25日 下午2:46:03

* @version 1.0

*/

public class User {

    private String username;

    private String password;

    public String getUsername() {

        return username;

    }

    public void setUsername(String username) {

        this.username = username;

    }

    public String getPassword() {

        return password;

    }

    public void setPassword(String password) {

        this.password = password;

    }

    @Override

    public String toString() {

        return "User [username=" + username + ", password=" + password + "]";

    }

}

JdbcUtils.java

package com.pers.jdbc.utils;

import java.io.IOException;

import java.io.InputStream;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

import java.util.Properties;

/**

* @author liangyadong

* @date 2016年10月13日 下午3:23:22

* @version 1.0

*/

public class JdbcUtils {

    public static final String DRIVERCLASS;

    public static final String URL;

    public static final String USERNAME;

    public static final String PASSWORD;

    /**

     * 静态代码块

     *

     * 步骤

     * 1.创建properties对象

     * 2.获取db配置文件的输入流

     * 3.properties对象加载配置文件

     * 4.properties对象通过key获取值

     */

    static{

        // 读取配置文件,将值赋给常量

        // 创建properties对象

        Properties pro = new Properties();

        // 获取db.properties文件的输入流

        InputStream in = JdbcUtils.class.getClassLoader().getResourceAsStream("com/pers/jdbc/utils/db.properties");

        // 加载配置文件

        try {

            pro.load(in);

        } catch (IOException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

        // 通过key获取值

        DRIVERCLASS = pro.getProperty("driverClass");

        URL = pro.getProperty("url");

        USERNAME = pro.getProperty("username");

        PASSWORD = pro.getProperty("password");

    }

    /**

     * 加载驱动

     */

    public static void loadDriver(){

        try {

            Class.forName(DRIVERCLASS);

        } catch (ClassNotFoundException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

    }

    /**

     * 获取连接

     * @return

     */

    public static Connection getConnection() {

        // TODO Auto-generated method stub

        // 加载驱动

        loadDriver();

        try {

            // 获取连接

            return DriverManager.getConnection(URL,USERNAME,PASSWORD);

        } catch (SQLException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

        return null;

    }

    /**

     * 释放资源

     *

     * 查询的释放资源方法

     * @param conn

     * @param sta

     * @param rs

     */

    public static void release(Connection conn,Statement sta,ResultSet rs){

        if (rs!=null) {

            try {

                rs.close();

            } catch (SQLException e) {

                // TODO Auto-generated catch block

                e.printStackTrace();

            }

            rs = null;

        }

        if (sta!=null) {

            try {

                sta.close();

            } catch (SQLException e) {

                // TODO Auto-generated catch block

                e.printStackTrace();

            }

            sta = null;

        }

        if (conn!=null) {

            try {

                conn.close();

            } catch (SQLException e) {

                // TODO Auto-generated catch block

                e.printStackTrace();

            }

            conn = null;

        }

    }

    /**

     * 释放资源

     *

     * 增删改的释放资源方法

     * @param conn

     * @param sta

     */

    public static void release(Connection conn,Statement sta){

        if (sta!=null) {

            try {

                sta.close();

            } catch (SQLException e) {

                // TODO Auto-generated catch block

                e.printStackTrace();

            }

            sta = null;

        }

        if (conn!=null) {

            try {

                conn.close();

            } catch (SQLException e) {

                // TODO Auto-generated catch block

                e.printStackTrace();

            }

            conn = null;

        }

    }

}

db.properties

driverClass=com.mysql.jdbc.Driver

url=jdbc:mysql:///myTest

username=root

password=root

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