JPA怎么通过Specification实现复杂查询

小编给大家分享一下JPA怎么通过Specification实现复杂查询，希望大家阅读完这篇文章之后都有所收获，下面让我们一起去探讨吧！

JPA 通过Specification实现复杂查询

JPA中继承BaseRepo之后，可以使用最基本的增删改查，如果想实现复杂查询，则需要借助Specification来完成这个功能：

下面就简单介绍一下Specification的使用

public void findAll(ConstructPlanPageReqEntity constructPlanPageReqEntity) {        Integer pageNum = page.getPageNum();        Integer pageSize = page.getPageSize();        String costType = constructPlanPageReqEntity.getCostType();        String name = constructPlanPageReqEntity.getName();        String planMoneyStart = constructPlanPageReqEntity.getPlanMoneyStart();        String planMoneyEnd = constructPlanPageReqEntity.getPlanMoneyEnd();        String singMoneyEnd = constructPlanPageReqEntity.getSingMoneyEnd();        String signMoneyStart = constructPlanPageReqEntity.getSignMoneyStart();        long projectId = Long.parseLong(constructPlanPageReqEntity.getProjectId());        String status = constructPlanPageReqEntity.getStatus();        //分页        pageNum=pageNum-1;        Pageable pageable = PageRequest.of(pageNum, pageSize);//多条件匹配查询        Specification specification= new Specification() {            @Override            public Predicate toPredicate(Root root, CriteriaQuery criteriaQuery, CriteriaBuilder criteriaBuilder) {                ArrayList list = new ArrayList<>();                Path costType1 = root.get("costType");                Path name1 = root.get("name");                Path projectId1 = root.get("projectId");                Path