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2.Java+Servlet+JDBC连接数据库操作

来源：独旅网

Java+Servlet+JDBC连接数据库操作（简单案例）

1.理解三层架构

简单理解：servlet相当于前端页面（可以接受来自前端发出的请求），在sevlet类中声明service对象，进而实现对service层的调用（调用其方法），在service实现类中声明Dao对象，实现对Dao层的调用（调用其方法)。这就是所谓的三层架构。

2.具体实现过程

（1）导入项目所需要的包：JDK，Servlet，mysql驱动包（缺一不可），创建好各层包名。

（2）目录代码文件

register.jsp

//register.jsp
<%@ 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>注册页面</title>
</head>
<body>
  <h1>欢迎大家来访问本系统</h1>
  <form action=" /ServletDemo/register" method="post">
       用户名：<input type="text" name="username"/><br/>
       密码：   <input type="password" name="pwd"/><br/>
       邮箱：<input type="text" name="email"/><br/>
       <input type="submit" value="注册"/><input type="reset"/>
  
  </form>
</body>
</html>

web.xml

<!--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>ServletDemo</display-name>
    <!-- 配置注册请求的Servlet -->
    <servlet>
     <servlet-name>registerServlet</servlet-name>
     <servlet-class>com.icss.web.RegisterServlet</servlet-class>
    </servlet>
    <servlet-mapping>
    <servlet-name>registerServlet</servlet-name>
    <url-pattern>/register</url-pattern>
    </servlet-mapping>
</web-app>

RegisterServlet.java

package com.icss.web;

import java.io.IOException;
import java.util.Date;

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

import com.icss.pojo.RegUser;
import com.icss.service.UserService;
import com.icss.service.impl.UserServiceImpl;

public class RegisterServlet extends HttpServlet {
     //alt+/会有代码提示
	
	//定义Service层
	private UserService userService=new UserServiceImpl();
	@Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    	
    }
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse resp) throws ServletException, IOException {
       
    	
    	RegUser user=new RegUser();
       System.out.println("注册请求到达了我的Servlet");
       String uname = request.getParameter("username");
       String pwd = request.getParameter("pwd");
       String email = request.getParameter("email");
       user.setUsername(uname);
       user.setPassword(pwd);
       user.setEmail(email);
       user.setRegTime(new Date());
       
       //调用service层，注册用户
       userService.registerUser(user);
    }
}

UserService.java

package com.icss.service;

import com.icss.pojo.RegUser;

public interface UserService {
    public void registerUser(RegUser user);
}

UserServiceImpl

package com.icss.service.impl;

import com.icss.dao.UserDao;
import com.icss.dao.impl.UserDaoImpl;
import com.icss.pojo.RegUser;
import com.icss.service.UserService;

public class UserServiceImpl implements UserService {

	//定义一个Dao层对象
	private UserDao userDao=new UserDaoImpl();
	@Override
	public void registerUser(RegUser user) {
		// TODO 自动生成的方法存根
		userDao.registerUser(user);
	}

}

RegUser.java

package com.icss.pojo;

import java.util.Date;

public class RegUser {
	private String username;
	private String password;
	private String email;
	private Date regTime;

	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;
	}

	public String getEmail() {
		return email;
	}

	public void setEmail(String email) {
		this.email = email;
	}

	public Date getRegTime() {
		return regTime;
	}

	public void setRegTime(Date regTime) {
		this.regTime = regTime;
	}

	@Override
	public String toString() {
		return "RegUser [username=" + username + ", password=" + password + ", email=" + email + ", regTime=" + regTime
				+ "]";
	}
	
}

UserDao.java

package com.icss.dao;

import com.icss.pojo.RegUser;

public interface UserDao {

	public void registerUser(RegUser user);
		// TODO 自动生成的方法存根
}

UserDaoImpl.java

package com.icss.dao.impl;

import java.sql.Connection;
import java.sql.DriverManager;
import java.text.SimpleDateFormat;

import com.icss.dao.UserDao;
import com.icss.pojo.RegUser;
import com.mysql.jdbc.PreparedStatement;

public class UserDaoImpl implements UserDao {

	@Override
	public void registerUser(RegUser user) {
		// TODO 自动生成的方法存根
		
		try {
			//1.注册驱动
			Class.forName("com.mysql.jdbc.Driver");
			
			//2.获得数据库连接对象
			Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "root");
			
			//3.定义sql语句
			String sql="INSERT INTO USER VALUES(NULL,?,?,?,?)";
			PreparedStatement statement=(PreparedStatement) connection.prepareStatement(sql);
			
			//4.执行sql语句
			statement.setString(1, user.getUsername());
			statement.setString(2, user.getPassword());
			statement.setString(3, user.getEmail());
			
			//把Datar日期转为字符串传递到数据
			SimpleDateFormat simpleDateFormat=new SimpleDateFormat("yyyy-MM-dd");
			statement.setString(4, simpleDateFormat.format(user.getRegTime()));
			
			
			//5.执行sql语句
			statement.executeUpdate();
			
			//6.关闭连接
			statement.close();
			connection.close();
		} catch (Exception e) {
			// TODO 自动生成的 catch 块
			e.printStackTrace();
		}
	}

}

下面是创建的数据表（我用的是SQLyog管理数据库）。

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