MyBatis-Plus联表查询(Mybatis-Plus-Join)

支持连表查询的mybatis-plus,mybatis-plus风格的连表操作提供 wrapper.leftJoin() wrapper.rightJoin()等操作

<dependency>
    <groupId>com.github.yulichang</groupId>
    <artifactId>mybatis-plus-join-boot-starter</artifactId>
    <version>1.4.4</version>
</dependency>

注意: mybatis plus version >= 3.3.0

参考：https://blog.csdn.net/tongxin_tongmeng/article/details/128627980

1.将代码生成的mapper改为继承MPJBaseMapper (必选)

2.将代码生成的service继承MPJBaseService (可选)

3.将代码生成的serviceImpl继承MPJBaseServiceImpl (可选)

注意：需要连接的表都进行代码生成和上述继承类变更。

1.原始SQL
SELECT
   bbb.symbol_id,
   aaa.intepn,
   aaa.componen_id,
   ccc.supppn,
   ddd.symbolinctimestamp
FROM
   librarygraphic bbb
   LEFT JOIN componen aaa ON bbb.componen_id = aaa.componen_id
   LEFT JOIN supppart ccc ON aaa.componen_id = ccc.componen_id
   LEFT JOIN logicsymbol ddd ON bbb.symbol_id = ddd.symbol_id
WHERE
   bbb.symbol_id IS NOT NULL
   AND aaa.intepn IS NOT NULL
   AND ddd.symbolinctimestamp IS NOT NULL
   AND aaa.grpname='Connector'
   AND aaa.latest = 1

2.视图实体(封装查询结果)
@Data
public class LibrarygraphicBo {

    private String symbolId;

    private String intepn;

    private String componenId;

    private String supppn;

    private String symbolinctimestamp;

}

3.Mybatis-Plus-Join
MPJLambdaWrapper<Librarygraphic> wrapper = new MPJLambdaWrapper<Librarygraphic>()
        .selectAs(Librarygraphic::getSymbolId, LibrarygraphicBo::getSymbolId)
        .selectAs(Componen::getIntepn, LibrarygraphicBo::getIntepn)
        .selectAs(Componen::getComponenId, LibrarygraphicBo::getComponenId)
        .selectAs(Supppart::getSupppn, LibrarygraphicBo::getSupppn)
        .selectAs(Logicsymbol::getSymbolinctimestamp, LibrarygraphicBo::getSymbolinctimestamp)
        .leftJoin(Componen.class, Componen::getComponenId, Librarygraphic::getComponenId)
        .leftJoin(Supppart.class, Supppart::getComponenId, Componen::getComponenId)
        .leftJoin(Logicsymbol.class, Logicsymbol::getSymbolId, Librarygraphic::getSymbolId)
        .isNotNull(Librarygraphic::getSymbolId)
        .isNotNull(Componen::getIntepn)
        .isNotNull(Logicsymbol::getSymbolinctimestamp)
        .eq(Componen::getGrpname, "Connector")
        .eq(Componen::getLatest, 1);

List<LibrarygraphicBo> boList = librarygraphicMapper.selectJoinList(LibrarygraphicBo.class, wrapper);

注意：最终查询结果封装到了LibrarygraphicBo类型的集合

https://gitee.com/best_handsome/mybatis-plus-join