JavaWeb入门——MVC

1.MVC设计模式

1.1MVC模式

1.2MVC模式示例

index.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
        <a href="WelcomeServlet">WelcomeServlet</a>
        
        <form action="WelcomeServlet" method="post">
            <input type="submit"/>
        </form>
</body>
</html>

WelcomeServlet.java

package com.wjc.servlet;

import java.io.IOException;

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

public class WelcomeServlet extends HttpServlet{
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("doGet...");
    }
    
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("doPost...");
    }
}

web.xml

···
  <servlet>
    <servlet-name>WelcomeServlet</servlet-name>
    <servlet-class>com.wjc.servlet.WelcomeServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>WelcomeServlet</servlet-name>
    <url-pattern>/WelcomeServlet</url-pattern>
  </servlet-mapping>
</web-app>

1.3Servlet执行流程

1.4Servlet2.5与Servlet3.0的区别

1.5 / 的使用

1.6Servlet的生命周期

1.7Servlet继承关系

ServletAPI的详解与源码分析可以多看两遍

1.8MVC案例实现

项目目录

login.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ page import="com.wjc.servlet.LoginServlet" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>登录</title>
</head>
<body>
        <form action="LoginServlet" method="post">
            用户名：<input type="text" name="uname"><br/>
            密码：<input type="password" name="upwd"><br/>
            <input type="submit" value="登录"><br/>
        </form>
</body>
</html>

LoginServlet.java
package com.wjc.servlet;

import java.io.IOException;

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

import com.wjc.dao.LoginDao;
import com.wjc.entity.LoginData;

//控制器层：接受view请求，并分发给Model处理
public class LoginServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //处理登录
        request.setCharacterEncoding("utf-8");
        String name = request.getParameter("uname");
        String password = request.getParameter("upwd");
        
        LoginData login = new LoginData(name, password);//用户名和密码
        
        //调用模型层的登录功能
        int result = LoginDao.login(login);
        
        if(result > 0) {//成功
            response.sendRedirect("welcome.jsp");
        }else {//跳回重新登陆
            response.sendRedirect("login.jsp");
        }

    }

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

LoginDao.java
package com.wjc.dao;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import com.wjc.entity.LoginData;

//模型层：用于处理登录（查询数据）
public class LoginDao {
    public static int login(LoginData login) {//登录
        int flag = 0;//登陆成功或失败的标识 1: 0: -1:
        int result = 0;
        
        Connection connection = null;
        PreparedStatement pstmt = null;
        ResultSet rs = null;
        
        String URL = "jdbc:mysql://localhost:3306/test?useSSL=false&serverTimezone=UTC";
        String UNAME = "root";
        String UPWD = "diang520";
        
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            connection = DriverManager.getConnection(URL,UNAME,UPWD);
            
            String sql = "select count(*) from login where name = ? and password =?;";
            pstmt = connection.prepareStatement(sql);
            pstmt.setString(1, login.getName());
            pstmt.setString(2, login.getPassword());

            rs = pstmt.executeQuery();
            if(rs.next()) {
                result = rs.getInt(1);
            }
            if(result > 0) {
                flag = 1;
            }
            
            return flag;
            
        }catch(ClassNotFoundException e) {
            e.printStackTrace();
            return -1;
        }catch(SQLException e) {
            e.printStackTrace();
            return -1;
        }catch(Exception e) {
            e.printStackTrace();
            return -1;
        }finally {
            try {
                if(rs != null) rs.close();
                if(pstmt != null) pstmt.close();
                if(connection != null) connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

LoginData.java
package com.wjc.entity;

public class LoginData {
    private String name;
    private String password;
    public LoginData() {
    }
    public LoginData(String name, String password) {
        super();
        this.name = name;
        this.password = password;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
}

Welcome.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
    登陆成功，欢迎你！
</body>
</html>