用springboot mybatis写一个增删改查

首先，在pom.xml文件中添加Spring Boot、MyBatis和MySQL的相关依赖：

<dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.mybatis.spring.boot</groupId><artifactId>mybatis-spring-boot-starter</artifactId></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><scope>runtime</scope></dependency>
</dependencies>

接下来，创建一个实体类User.java代表用户信息：

public class User {private Long id;private String username;private String password;// 省略getter和setter方法
}

然后，创建一个Mapper接口UserMapper.java用于定义增删改查的方法：

public interface UserMapper {User selectUserById(Long id);List<User> selectAllUsers();void insertUser(User user);void updateUser(User user);void deleteUserById(Long id);
}

接着，在resources目录下创建一个mapper目录，并在该目录下创建UserMapper.xml文件，配置具体的SQL语句：

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.example.mapper.UserMapper"><resultMap id="userResultMap" type="com.example.entity.User"><id property="id" column="id"/><result property="username" column="username"/><result property="password" column="password"/></resultMap><select id="selectUserById" resultMap="userResultMap">SELECT * FROM user WHERE id = #{id}</select><select id="selectAllUsers" resultMap="userResultMap">SELECT * FROM user</select><insert id="insertUser">INSERT INTO user (username, password) VALUES (#{username}, #{password})</insert><update id="updateUser">UPDATE user SET username = #{username}, password = #{password} WHERE id = #{id}</update><delete id="deleteUserById">DELETE FROM user WHERE id = #{id}</delete>
</mapper>

最后，创建一个UserController.java作为控制器，注入UserMapper并实现增删改查的功能：

@RestController
public class UserController {@Autowiredprivate UserMapper userMapper;@GetMapping("/users/{id}")public User getUserById(@PathVariable Long id) {return userMapper.selectUserById(id);}@GetMapping("/users")public List<User> getAllUsers() {return userMapper.selectAllUsers();}@PostMapping("/users")public void addUser(@RequestBody User user) {userMapper.insertUser(user);}@PutMapping("/users/{id}")public void updateUser(@PathVariable Long id, @RequestBody User user) {user.setId(id);userMapper.updateUser(user);}@DeleteMapping("/users/{id}")public void deleteUser(@PathVariable Long id) {userMapper.deleteUserById(id);}
}