Spring JPA连表查询重复关联如何解决？

spring jpa 连表重复 join 解决方案

为了解决 userentity 和 userarchiveentity 之间重复的 userarchive 关联，可以在 specification 中手动指定连接类型。修改后的代码如下：

specification specification = (root, query, criteriabuilder) -> {
    predicate predicate = criteriabuilder.conjunction();
    join userarchiveentityjoin = root.join("userarchive", jointype.left);
    return predicate;
};

对于不同的业务场景需要不同的模型关联，spring jpa 无法提供针对不同关联要求的方法重载。可以使用依赖注入来解决此问题：

@Repository
public class UserRepositoryImpl implements UserRepos
itoryCustom {

    @Autowired
    private UserRepository userRepository;

    @Override
    public Page findAllWithUserArchive(Specification specification, Pageable pageable) {
        EntityGraph entityGraph = EntityGraph.of(UserEntity.class)
                .addSubgraph("userArchive");
        return userRepository.findAll(specification, pageable, entityGraph);
    }

    @Override
    public Page findAllWithUserArchiveAndNation(Specification specification, Pageable pageable) {
        EntityGraph entityGraph = EntityGraph.of(UserEntity.class)
                .addSubgraph("userArchive")
                .addSubgraph("userArchive.nation");
        return userRepository.findAll(specification, pageable, entityGraph);
    }
}