运用spring boot框架用@RestController@RequestParam@Autowired@PostMapping@Service@Mapper@Data注解和xml<select>语句用resultType数据库mysql实现用户登录案例

以下是一个简单的spring boot框架下实现用户登录的示例代码：

User.java

package com.example.demo.model;

import lombok.Data;

@Data
public class User {
    private String username;
    private String password;
}

UserMapper.java

package com.example.demo.mapper;

import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;

import com.example.demo.model.User;

@Mapper
public interface UserMapper {
    @Select("SELECT * FROM user WHERE username=#{username} AND password=#{password}")
    User login(@Param("username") String username, @Param("password") String password);
}

UserService.java

package com.example.demo.service;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import com.example.demo.mapper.UserMapper;
import com.example.demo.model.User;

@Service
public class UserService {
    @Autowired
    private UserMapper userMapper;

    public User login(String username, String password) {
        return userMapper.login(username, password);
    }
}

UserController.java

package com.example.demo.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import com.example.demo.model.User;
import com.example.demo.service.UserService;

@RestController
public class UserController {
    @Autowired
    private UserService userService;

    @PostMapping("/login")
    public String login(@RequestParam String username, @RequestParam String password) {
        User user = userService.login(username, password);
        if (user == null) {
            return "登录失败";
        } else {
            return "登录成功";
        }
    }
}

application.properties

spring.datasource.url=jdbc:mysql://localhost:3306/test?useSSL=false&serverTimezone=UTC
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

以上代码中，使用了@RestController注解将UserController声明为一个控制器，@PostMapping注解将login方法映射到/login接口，@RequestParam注解用于接收请求参数，@Autowired注解用于依赖注入，@Service注解用于声明UserService为一个服务，@Mapper注解用于声明UserMapper为一个Mapper，@Data注解用于自动生成getter、setter和toString方法。在UserMapper中使用了<select>语句和resultType属性实现了查询，同时使用了@Param注解指定参数名。application.properties中配置了数据库连接信息。这样，当用户访问/login接口时，会调用UserController的login方法，该方法调用了UserService的login方法，后者又调用了UserMapper的login方法，最终返回用户登录信息。