1. javaBean+jsp+servlet (MVC)开发模式
MVC M(模型)用于处理应用程序数据逻辑的部分通常模型对象负责在数据库中存取数据。V(视图)应用程序中处理数据显示的部分通常视图是依据模型数据创建的。C(控制器)应用程序中处理用户交互的部分通常控制器负责从视图读取数据,控制用户输入,并向模型发送数据。
MVC适合用来开发web应用,下面用servlet+jsp+javaBean来实现简单的用户登录功能,梳理一下mvc模式的思路。
2.目录结构与数据库表
3.分层架构编写
3.1domain
domain层,编写实体类映射数据库的表,数据要和数据库表的段对应
//User.java
package UserBean;
public class User {
private int id;
private String password;
private String name;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "User [id=" + id + ", name=" + name + ", password=" + password + "]";
}
}
3.2 Dao层
编写接口类实现后可对数据库数据进行操作
//UserDao.java
package UserBean;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
public interface UserDao {
public ResultSet find(Connection conn,User user)throws SQLException;
}
//实现UserDao接口,他与数据库打交道
package Userimpl;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import UserBean.User;
import UserBean.UserDao;
public class UserDaoimpl implements UserDao{
@Override
public ResultSet find(Connection conn, User user) throws SQLException {
PreparedStatement ps=conn.
prepareStatement("select * from tbl_user where name=?and password=?");
ps.setString(1, user.getName());//验证uaername值
ps.setString(2, user.getPassword());//验证password值
return ps.executeQuery();//执行并返回一个结果集
}
}
提供链接数据库的操作
//CheckUserService.java
package UserBean;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import Userimpl.UserDaoimpl;
public class CheckUserService {
private UserDao oneuser=new UserDaoimpl();
public boolean check(User user){
Connection conn=null;
try {
Class.forName("com.mysql.cj.jdbc.Driver");
conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/mvc_db?verifyServerCertificate=false&useSSL=false&serverTimezone=UTC","root","123456");
System.out.println("已经连接到mysql");
ResultSet rs=oneuser.find(conn, user);//得到查询结果
while(rs.next()){
return true;
}
} catch (Exception e) {
e.printStackTrace();
}finally{
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
return false;
}
}
CheckUserService这里因为我使用mysql8数据库所以导jar包时注意,还有连接时的URL和mysql5不一样
应该是
jdbc:mysql://localhost:3306/mvc_db?verifyServerCertificate=false&useSSL=false&serverTimezone=UTC
3.3 servlet层
//接下来就是编写和前端页面打交道的servlet了
package servlet;
import java.io.IOException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import UserBean.CheckUserService;
import UserBean.User;
public class CheckServlet extends HttpServlet {
private CheckUserService cus=new CheckUserService();
public CheckServlet() {
super();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String usn=request.getParameter("userName");//从前台取得username值
String psw=request.getParameter("passWord");//从前台取得password值
RequestDispatcher rd=null;
String forward=null;
if(usn==null||psw==null){
rd=request.getRequestDispatcher("/adm/error.jsp");
rd.forward(request, response);
}else{
User user=new User();
user.setName(usn);
user.setPassword(psw);
boolean bl=cus.check(user);
if(bl){
forward="/adm/success.jsp";
}else{
forward="/adm/error.jsp";
}
rd=request.getRequestDispatcher(forward);
rd.forward(request, response);
}
}
}
注意着里的命名要和jsp页面的name属性一样
另外forward后面的URL路径默认是从webcontent目录下查找
//web.xml配置servlet路径
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd" id="WebApp_ID" version="4.0">
<servlet>
<servlet-name>CheckServlet</servlet-name>
<servlet-class>servlet.CheckServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>CheckServlet</servlet-name>
<url-pattern>/CheckServlet</url-pattern>
</servlet-mapping>
</web-app>
接下来就是前端jsp页面了,因为是一个简单的登录验证,所以前端页面就随便写了一下,喜欢好看的界面的可以去学习一下css3
//login.jsp
//用户登录页面
<%@ 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>
<form action="<%=request.getContextPath()%>/CheckServlet" method="post">
用户名:<input type="text" name="userName"><br>
密 码:<input type="password" name="passWord"><br>
<input type="submit" value="登录">
<input type="reset" value="重置">
</form>
</body>
</html>
//success.jsp
//登陆成功页面
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>登录失败</title>
</head>
<body>
登陆失败!<br>
用户名或密码错误<br>
<a href="/adm/login.jsp">重新登录</a>
</body>
</html>
//error.jsp
//登录失败页面
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>登录失败</title>
</head>
<body>
登陆失败!<br>
用户名或密码错误<br>
<a href="/adm/login.jsp">重新登录</a>
</body>
</html>
好了,接下来就是验证成果的时候了。Run As一下,去浏览器输入
localhost:8080/servlet-exercise/adm/login.jsp
就可以验证了
由于没有配置默认访问目录所以直接点放回登录页面不可以。
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