Spring Data JPA 自定义条件查询分页

• 1.Repository额外继承JpaSpecificationExecutor

public interface CommentRepository
    extends JpaRepository, JpaSpecificationExecutor {
}```




# 2.在Service处理分页条件

```java
int page =
        (object.containsKey("page")
                && object.getInteger("page") != null
                && object.getInteger("page") > 0)
            ? object.getInteger("page")
            : 1;
    int size =
        (object.containsKey("size")
                && object.getInteger("size") != null
                && object.getInteger("size") > 0)
            ? object.getInteger("size")
            : 20;

	//  Sort.by(Sort.Direction.ASC, "createdTime") 排序条件
    Pageable pageable = PageRequest.of(page - 1, size, Sort.by(Sort.Direction.ASC, "createdTime"));
    // 若含有条件查询，则需要 Specification 进行拼接
	//Root：查询哪个表
	//CriteriaQuery：查询哪些字段，排序是什么
	//CriteriaBuilder：字段之间是什么关系，如何生成一个查询条件，每一个查询条件都是什么方式
	//Predicate（expression）：单独每一条查询条件的详细描述
	Specification specification =
          (root, criteriaQuery, criteriaBuilder) -> {
            List predicateList = new ArrayList<>();
        	// 若要进行模糊查询注意需要单独拼接‘%’，或者前端返回时直接拼接好
        	// 多条件查询可以获取所有属性后匹配
       		Map innerMap = object.getInnerMap();
        	// 获取实体类的所有属性信息
          	Set> attributes = root.getModel().getAttributes();
          	List attributeNameList =
              attributes.stream().map(Attribute::getName).collect(Collectors.toList());
          	for (Map.Entry entry : innerMap.entrySet()) {
                // 判断是否含有当前字段
            	if (attributeNameList.contains(entry.getKey())) {
              	Predicate namePredicate =
                  	criteriaBuilder.like(root.get(entry.getKey()), "%" + entry.getValue() + "%");
              	predicateList.add(namePredicate);
            	}
          	}
            Predicate namePredicate =
                criteriaBuilder.like(
                    root.get("content"), "%" + object.getString("fuzzyQuery") + "%");
            CriteriaBuilder.In uidIn = criteriaBuilder.in(root.get("uid"));
            for (String messageId : messageIds) {
              uidIn.value(messageId);
            }
            Predicate createdTime =
                criteriaBuilder.between(root.get("createdTime"), dateTime, new Date());
            Predicate predicate = criteriaBuilder.and(uidIn);
            predicateList.add(namePredicate);
            predicateList.add(predicate);
            predicateList.add(createdTime);
        	//排序可以在此加入，也可以在pageable指定
         	//Order createdTimeOrder = criteriaBuilder.asc(root.get("createdTime"));
            //return criteriaQuery.orderBy(createdTimeOrder).where(predicateList.toArray(new Predicate[predicateList.size()])).getRestriction();
            return criteriaBuilder.and(predicateList.toArray(new Predicate[predicateList.size()]));
          };
   Page commentPage = commentRepository.findAll(specification, pageable);