【Java】servlet用户登录案例

案例：用户登录

* 用户登录案例需求：
1.编写login.html登录页面
username & password 两个输入框
2.使用Druid数据库连接池技术,操作mysql，day14数据库中user表
3.使用JdbcTemplate技术封装JDBC
4.登录成功跳转到SuccessServlet展示：登录成功！用户名,欢迎您
5.登录失败跳转到FailServlet展示：登录失败，用户名或密码错误

开发步骤

项目结构

创建项目，导入html页面，配置文件，jar包

创建数据库环境

CREATE DATABASE day14;
USE day14;
CREATE TABLE USER(
id INT PRIMARY KEY AUTO_INCREMENT,
username VARCHAR(32) UNIQUE NOT NULL,
PASSWORD VARCHAR(32) NOT NULL
);

创建包cn.itcast.domain,创建类User

package cn.itcast.domain;

/**
* 用户的实体类
*/
public class User {

private int id;
private String username;
private String password;

private String gender;

public void setHehe(String gender){
this.gender = gender;
}

public String getHehe(){
return gender;
}

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;
}

@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", password='" + password + '\'' +
", gender='" + gender + '\'' +
'}';
}
}

创建包cn.itcast.util,编写工具类JDBCUtils

package cn.itcast.util;

import com.alibaba.druid.pool.DruidDataSourceFactory;

import javax.sql.DataSource;
import javax.xml.crypto.Data;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;

/**
* JDBC工具类 使用Durid连接池
*/
public class JDBCUtils {

private static DataSource ds ;

static {

try {
//1.加载配置文件
Properties pro = new Properties();
//使用ClassLoader加载配置文件，获取字节输入流
InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties");
pro.load(is);

//2.初始化连接池对象
ds = DruidDataSourceFactory.createDataSource(pro);

} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}

/**
* 获取连接池对象
*/
public static DataSource getDataSource(){
return ds;
}


/**
* 获取连接Connection对象
*/
public static Connection getConnection() throws SQLException {
return ds.getConnection();
}
}

上述代码读取的配置文件druid.properties的内容如下

创建包cn.itcast.dao,创建类UserDao,提供login方法

package cn.itcast.dao;

import cn.itcast.domain.User;
import cn.itcast.util.JDBCUtils;
import org.springframework.dao.DataAccessException;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;

/**
* 操作数据库中User表的类
*/
public class UserDao {

//声明JDBCTemplate对象共用
private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());

/**
* 登录方法
* @param loginUser 只有用户名和密码
* @return user包含用户全部数据,没有查询到，返回null
*/
public User login(User loginUser){
try {
//1.编写sql
String sql = "select * from user where username = ? and password = ?";
//2.调用query方法
User user = template.queryForObject(sql,
new BeanPropertyRowMapper<User>(User.class),
loginUser.getUsername(), loginUser.getPassword());


return user;
} catch (DataAccessException e) {
e.printStackTrace();//记录日志
return null;
}
}
}

测试UserDao类

package cn.itcast.test;

import cn.itcast.dao.UserDao;
import cn.itcast.domain.User;
import org.junit.Test;

public class UserDaoTest {



@Test
public void testLogin(){
User loginuser = new User();
loginuser.setUsername("superbaby");
loginuser.setPassword("123111");


UserDao dao = new UserDao();
User user = dao.login(loginuser);

System.out.println(user);
}
}

编写cn.itcast.web.servlet.LoginServlet类

package cn.itcast.web.servlet;

import cn.itcast.dao.UserDao;
import cn.itcast.domain.User;
import org.apache.commons.beanutils.BeanUtils;

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 java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.util.Map;


@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {


@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//1.设置编码
req.setCharacterEncoding("utf-8");
/* //2.获取请求参数
String username = req.getParameter("username");
String password = req.getParameter("password");
//3.封装user对象
User loginUser = new User();
loginUser.setUsername(username);
loginUser.setPassword(password);*/
//2.获取所有请求参数
Map<String, String[]> map = req.getParameterMap();
//3.创建User对象
User loginUser = new User();
//3.2使用BeanUtils封装
try {
BeanUtils.populate(loginUser,map); //用 BeanUtils把存储请求参数的map封装为User对象
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}


//4.调用UserDao的login方法
UserDao dao = new UserDao();
User user = dao.login(loginUser);

//5.判断user
if(user == null){
//登录失败
req.getRequestDispatcher("/failServlet").forward(req,resp);
}else{
//登录成功
//存储数据
req.setAttribute("user",user);
//转发
req.getRequestDispatcher("/successServlet").forward(req,resp);
}

}

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doGet(req,resp);
}
}

编写FailServlet和SuccessServlet类

failServlet类

package cn.itcast.web.servlet;

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 java.io.IOException;

@WebServlet("/failServlet")
public class FailServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//给页面写一句话

//设置编码
response.setContentType("text/html;charset=utf-8");
//输出
response.getWriter().write("登录失败，用户名或密码错误");

}

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

SuccessServlet类

package cn.itcast.web.servlet;

import cn.itcast.domain.User;

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 java.io.IOException;

@WebServlet("/successServlet")
public class SuccessServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//获取request域中共享的user对象
User user = (User) request.getAttribute("user");

if(user != null){
//给页面写一句话

//设置编码
response.setContentType("text/html;charset=utf-8");
//输出
response.getWriter().write("登录成功！"+user.getUsername()+",欢迎您");
}


}

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

login.html中form表单的action路径的写法
* 虚拟目录+Servlet的资源路径

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<form action="/day14_test/loginServlet" 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">

</form>
</body>
</html>

BeanUtils工具类，简化数据封装

* 用于封装JavaBean的
1. JavaBean：标准的Java类
1. 要求：
1. 类必须被public修饰
2. 必须提供空参的构造器
3. 成员变量必须使用private修饰
4. 提供公共setter和getter方法
2. 功能：封装数据
2. 概念：
成员变量：
属性：setter和getter方法截取后的产物
例如：getUsername() --> Username--> username 这里的username成为属性
3. 方法：
1. setProperty()
2. getProperty()
3. populate(Object obj , Map map):将map集合的键值对信息，封装到对应的JavaBean对象中

要用BeanUtils需要先导入jar包

示例代码
setProperty是设置属性，而不是设置成员变量

package cn.itcast.test;

import cn.itcast.domain.User;
import org.apache.commons.beanutils.BeanUtils;
import org.testng.annotations.AfterTest;

import java.lang.reflect.InvocationTargetException;

public class BeanUtilsTest {

@org.junit.Test
public void test(){

User user = new User();
try {
BeanUtils.setProperty(user,"hehe","male");
System.out.println(user);

String gender = BeanUtils.getProperty(user, "hehe");
System.out.println(gender);
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
} catch (NoSuchMethodException e) {
e.printStackTrace();
}

}
}