【MyBatis Plus】MyBatis Plus框架

一.基础内容

1.1MyBatis Plus是国产的工具，IDEA不支持

MyBatis Plus是国产的工具，IDEA不支持，我们要手动导包。MyBatis Plus是包含了MyBatis的，所以，我们创建项目的时候，不要勾选MyBatis否则，会导致jar包冲突，引发错误。

1.2引入依赖

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.5.3.2</version>
</dependency>

1.3BaseMapper提供的方法

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package com.baomidou.mybatisplus.core.mapper;

import com.baomidou.mybatisplus.core.conditions.Wrapper;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.core.toolkit.Wrappers;
import java.io.Serializable;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.exceptions.TooManyResultsException;

public interface BaseMapper<T> extends Mapper<T> {
    int insert(T entity);

    int deleteById(Serializable id);

    int deleteById(T entity);

    default int deleteByMap(Map<String, Object> columnMap) {
        QueryWrapper<T> qw = Wrappers.query();
        return this.delete((Wrapper)qw.allEq(columnMap));
    }

    int delete(@Param("ew") Wrapper<T> queryWrapper);

    int deleteBatchIds(@Param("coll") Collection<?> idList);

    int updateById(@Param("et") T entity);

    int update(@Param("et") T entity, @Param("ew") Wrapper<T> updateWrapper);

    T selectById(Serializable id);

    List<T> selectBatchIds(@Param("coll") Collection<? extends Serializable> idList);

    default List<T> selectByMap(Map<String, Object> columnMap) {
        QueryWrapper<T> qw = Wrappers.query();
        return this.selectList((Wrapper)qw.allEq(columnMap));
    }

    default T selectOne(@Param("ew") Wrapper<T> queryWrapper) {
        return (T)this.selectOne(queryWrapper, true);
    }

    default T selectOne(@Param("ew") Wrapper<T> queryWrapper, boolean throwEx) {
        List<T> list = this.selectList(queryWrapper);
        int size = list.size();
        if (size == 1) {
            return (T)list.get(0);
        } else if (size > 1) {
            if (throwEx) {
                throw new TooManyResultsException("Expected one result (or null) to be returned by selectOne(), but found: " + list.size());
            } else {
                return (T)list.get(0);
            }
        } else {
            return null;
        }
    }

    default boolean exists(Wrapper<T> queryWrapper) {
        Long count = this.selectCount(queryWrapper);
        return null != count && count > 0L;
    }

    Long selectCount(@Param("ew") Wrapper<T> queryWrapper);

    List<T> selectList(@Param("ew") Wrapper<T> queryWrapper);

    List<T> selectList(IPage<T> page, @Param("ew") Wrapper<T> queryWrapper);

    List<Map<String, Object>> selectMaps(@Param("ew") Wrapper<T> queryWrapper);

    List<Map<String, Object>> selectMaps(IPage<? extends Map<String, Object>> page, @Param("ew") Wrapper<T> queryWrapper);

    List<Object> selectObjs(@Param("ew") Wrapper<T> queryWrapper);

    default <P extends IPage<T>> P selectPage(P page, @Param("ew") Wrapper<T> queryWrapper) {
        List<T> list = this.selectList(page, queryWrapper);
        page.setRecords(list);
        return page;
    }

    default <P extends IPage<Map<String, Object>>> P selectMapsPage(P page, @Param("ew") Wrapper<T> queryWrapper) {
        List<Map<String, Object>> list = this.selectMaps(page, queryWrapper);
        page.setRecords(list);
        return page;
    }
}

二.标签

2.1@TableName ：指定数据库表名

2.2@TableId(value="",type=IdType.AUTO ) : 指定主键字段和类型

2.3@TableField ： 匹配表的字段

2.4配置文件统一指定表的名称前缀