1月18日

一）完善CRUD功能
数据库表设计
在MySQL数据库中，创建user表：
sql
CREATE TABLE user (
id BIGINT AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(50) NOT NULL,
age INT NOT NULL
);
Mapper接口扩展
在UserMapper接口中补充CRUD方法：
java
@Mapper
public interface UserMapper {
@Select("SELECT * FROM user WHERE id = #{id}")
User selectById(Long id);

@Insert("INSERT INTO user (name, age) VALUES (#{name}, #{age})")
void insert(User user);

@Update("UPDATE user SET name = #{name}, age = #{age} WHERE id = #{id}")
void update(User user);

@Delete("DELETE FROM user WHERE id = #{id}")
void delete(Long id);

@Select("SELECT * FROM user")
List<User> selectAll();

}
Service层实现
创建UserService类，封装业务逻辑：
java
@Service
public class UserService {
@Autowired
private UserMapper userMapper;

public User getById(Long id) {
    return userMapper.selectById(id);
}

public void save(User user) {
    userMapper.insert(user);
}

public void update(User user) {
    userMapper.update(user);
}

public void delete(Long id) {
    userMapper.delete(id);
}

public List<User> getAll() {
    return userMapper.selectAll();
}

}