Java web登录案例

java web登录案例

登录案例需求

用户输入用户名和密码，若在数据库中存在提示登录成功，若在数据库中不存在提示登录失败

浏览器：输入服务器中的登录页面的地址，服务器解析命令将页面返回到浏览器。

点击登录按钮向服务器的servlet发送请求

servlet获取用户名和密码。与数据库中的表做比较。（三层架构）

servlet中创建loginservice调用方法，向service发送请求service创建dao调用方法，service在向dao发送

user为null登录失败

user不为null登录成功：向前台写入信息登录成功

步骤分析

1. 创建数据库和表结构
2. 创建动态的web项目
3. 导入必要的架包和工具类，同时创建动态的web项目的包结构util servlet service dao bean
4. 导入前端的静态的资源文件
5. 编写servlet获取用户名和密码判断信息是否存在
6. 编写dao时创建QueryRunner对象

登录案例后端具体实现

包结构

utils包中

package com.dzu.utils;

import java.sql.Connection;
import java.sql.SQLException;

import javax.sql.DataSource;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class DataSourceUtils {
	private static DataSource ds=new ComboPooledDataSource();
	
	//获取连接池
	public static DataSource getDataSource(){
		return ds;
	}
	
	//获取连接
	public static Connection getConnection() throws SQLException{
		return ds.getConnection();
	}
}

dao包中

package com.dzu.dao;

import java.sql.SQLException;

import javax.sql.DataSource;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;

import com.dzu.bean.User;
import com.dzu.utils.DataSourceUtils;

public class Logindao {

	public User getUsernameAndPwd(String username, String password) throws SQLException {
		// TODO Auto-generated method stub
		//创建QueryRunner
		QueryRunner qr=new QueryRunner(DataSourceUtils.getDataSource());
		//编写sql
		String sql="select * from user where username=? and password =?";
		//执行sql
		User user=qr.query(sql,new BeanHandler<User>(User.class),username,password);
		
		return user;
	}

}

service包中

package com.dzu.service;

import java.sql.SQLException;

import com.dzu.bean.User;
import com.dzu.dao.Logindao;


public class LoginService {

	public User getUserByUsernameAndPwd(String username,String password) throws SQLException {
		//创建logindao
		Logindao ld=new Logindao();
		
		return ld.getUsernameAndPwd(username,password);
	}

}

servlet包中

package com.dzu.servlet;

import java.io.IOException;
import java.sql.SQLException;

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.dzu.bean.User;
import com.dzu.service.LoginService;

/**
 * Servlet implementation class LoginServlet
 */
@WebServlet("/login")
public class LoginServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//获取请求的用户名和密码
		try {
			String username =request.getParameter("username");
			String password =request.getParameter("password"); 
			//处理响应的乱码问题
			response.setHeader("content-type", "text/html;charset=utf-8");
			//创建LoginService
			LoginService ls=new LoginService();
			User user=ls.getUserByUsernameAndPwd(username,password);
			
			if(user==null) {
				response.getWriter().println("error");
			}else { 
				response.getWriter().println(user.getUsername()+"登录成功");
			}
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		//调用service中的方法
		
		//根据返回的对象进行判断
		
		
	}

	/**
	 * @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);
	}

}

bean包中

package com.dzu.bean;

public class User {
	private int id;
	private String username;
	private String password;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	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;
	}	
}

数据库表

create table user(
			id int primary key auto_increment,
			username varchar(20),
			password varchar(20)
		);
		insert into user values(null,'tom','123');
		insert into user values(null,'jack','123');