Libaryapi

图书管理系统后台

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• mybayis 配置
• java

@Mapper
public interface UserMapper {
    // @Select ("select * from user")
    List<User> listUsers();
}

• yml

mybatis:
  mapper-locations: classpath:mapper/*.xml

• xml id为方法名
• 位置src/main/resources/mapper/User.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.example.libary.mapper.UserMapper">
    <select id="listUsers" resultType="com.example.libary.entity.User">
        select * from user
    </select>
</mapper>

• 分页

        <!--分页-->
<dependency>
    <groupId>com.github.pagehelper</groupId>
    <artifactId>pagehelper</artifactId>
    <version>5.3.0</version>
</dependency> 

• ctrl+alt+o 清除无用的导入
• ctrl+alt+l 格式化

常见错误 Source must not be null 未考虑异常情况

// 全局异常处理
@RestControllerAdvice
@Slf4j

public class ExceptionHandle {
    @ExceptionHandler(value = Exception.class)
    public Result exceptionError(Exception e){
        log.error("系统错误",e);
        return Result.error("系统错误");
    }
    @ExceptionHandler (value = ServiceException.class)
    public Result serviceExceptionError(ServiceException e) {
        log.error("业务异常", e);
        return Result.error(e.getMessage());
    }
}

public class ServiceException extends RuntimeException{
    public ServiceException(String code, String message) {
        super(message);
        this.code = code;
    }
}

清空表 
TRUNCATE TABLE admin;