看的黑马2019版JAVAWEB写的，加上了部分自己的理解，供备忘使用。
依赖工具：
Durid 连接池，SQLyog，Mysql 5.7
整体逻辑：
1、使用SQLyog连接数据库。供Utils类使用，Utils中主要是调用"druid.properties"配置文件（里面包含了SQL的密码等信息）。
2、DAO类（data acess object 数据访问对象类）中夹带SQL语句，负责查询访问数据库中的用户信息。
3、从DAO类中得到的用户信息，经过User类的封装，得到一个user对象。
4、通过得到的这个user对象，就可以在Servlet类中进行各种判断，从而进一步进行跳转等工作了。
JDBCUtils类
package cn.util;
import com.alibaba.druid.pool.DruidDataSourceFactory;
import com.sun.xml.internal.ws.policy.privateutil.PolicyUtils;
import javax.sql.DataSource;
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 getDateSource(){
return ds;
}
/**
* 获取连接connection对象
*/
public static Connection getConnection() throws SQLException{
return ds.getConnection();
}
}
DAO类
package cn.dao;
import cn.domain.User;
import cn.util.JDBCUtils;
import org.springframework.dao.DataAccessException;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
public class UserDao {
//声明JDBCTemplate 对象公用
private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDateSource());
public User login(User loginUser) {
try {
//1.编写sql 卡了个错误，要在sqlyog里面能跑才行，一开始错是因为sql语句错了
String sql = "select * from user where username = ? AND password = ?";
//调用query方法 .class (反射)
User user = template.queryForObject(sql, new BeanPropertyRowMapper<>(User.class)
, loginUser.getUsername(), loginUser.getPassword());
return user;
} catch (DataAccessException e) {
e.printStackTrace(); //后期不会打印文件，会记录到日志里面
return null;
}
}
}
User类
package cn.domain;
//用户实体类
public class User {
private int id;
private String username;
private String password;
public int getId() {
return id;
}
public String getUsername() {
return username;
}
public String getPassword() {
return password;
}
public void setId(int id) {
this.id = id;
}
public void setUsername(String username) {
this.username = username;
}
public void setPassword(String password) {
this.password = password;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", password='" + password + '\'' +
'}';
}
}
LoginServlet类
package cn.web;
import cn.dao.UserDao;
import cn.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("/loginServlet")
public class LoginServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doGet(request,response); //调用和doGet一样的方法
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1.设置编码
request.setCharacterEncoding("utf-8");
//2.获取请求参数
String username = request.getParameter("username");
String password = request.getParameter("password");
//3.封装当前尝试登入的loginuser对象
User loginuser = new User();
loginuser.setUsername(username);
loginuser.setPassword(password);
//4.调用userdao的login方法
UserDao dao = new UserDao();
User user = dao.login(loginuser); //这里的user就是查询到的user
//5.判断user
if(user == null){
//登入失败，转发跳转
request.getRequestDispatcher("/failServlet").forward(request,response);
}
else{
//登入成功 存储数据 & 转发到成功页面
//setAttribute作用域是整个会话期间，在所有的页面都使用这些数据的时候使用
request.setAttribute("user",user);
request.getRequestDispatcher("/successServlet").forward(request,response);
}
}
}
两个跳转页面：
FailServlet类
package cn.web;
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");
//输出到页面上
response.getWriter().write("登入失败，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.web;
import cn.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test对象 (User)是强制类型转换
User user = (User) request.getAttribute("user");
if(user != null) //严谨起见，防止空指针异常
{
//给页面写一句话
//设置编码
response.setContentType("text/html;charset=utf-8");
//输出到页面上
response.getWriter().write("登入成功," + user.getUsername() + "欢迎你");
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}