JPA多表联查笔记

上手比较麻烦，首次写需好好了解(root, query, builder)

        Specification<Object1> cation = (root, query, builder) -> {
            List<Predicate> predicates= new ArrayList<>();
            //单个条件
            if (StringUtils.hasText(params)) {
                predicates.add(builder.equal(root.get("fieId"), params));
            }
            //多条件or
            if (StringUtils.hasText(params)) {
                Predicate params1= builder.like(root.get("fieId1"), "%" + params+ "%");
                Predicate params2= builder.like(root.get("fieId2"), "%" + params+ "%");
                Predicate params3= builder.like(root.get("fieId3"), "%" + params+ "%");
                predicates.add(builder.or(params1, params2, params3));
            }
            //验证通过，多表联查
            if (StatusCodeConstant.INSURED.equals(status)) {
                predicates.add(builder.equal(root.get("status"), status));
                //此处在主表实体标注关联ID @OneToMany(mappedBy = "id")
    			//private List<Object2> object2;
                Join<Object1, Object2> join = root.join("object2", JoinType.LEFT);
                predicates.add(builder.between(builder.currentDate(), join.get("startDate"), join.get("endDate")));
            }
            //日期条件查询
            predicates.add(builder.not(builder.between(builder.currentDate(), join.get("startDate"), join.get("endDate"))));
            if (predicates.size() > 0) {
                return builder.and(predicates.toArray(new Predicate[predicates.size()]));
            }
            return builder.conjunction();
        };
        Pageable pageable = PageRequest.of(page - 1, size, Sort.by("fieId"));
        Page<Object1> pageInfo = object1Repository.findAll(cation, pageable);
    	//略标注简写，注意看源码JPA比较全面想要的都有
        return Result.success().put("data", pageInfo.getContent()).put("totalPages", pageInfo.getTotalPages()).put("page", page).put("count", pageInfo.getTotalElements());