SpringDataJPA之Specification复杂查询

前言

继上次SpringData-JPA之ExampleMatcher实例查询使用一会之后发现ExampleMatcher对日期的查询特别糟糕，所以才有了Specification查询的研究。

20200114:更新对JpaSpecificationExecutor的解析,Specification思路2,以及CriteriaBuilder +CriteriaQuery+Predicate+TypedQuery查询部分
20180811:根据所学所用，重新更新了文章，并增加了Pageable分页排序功能。

实现

对应的Repository需要实现JpaSpecificationExecutor接口

public interface EventRepository extends JpaRepository<Event, Integer> , JpaSpecificationExecutor<Event>{

Specification与Controller业务逻辑

 @GetMapping("/event/list")public ApiReturnObject findAllEvent(String eventTitle,Timestamp registerTime,Integer pageNumber,Integer pageSize) {if(pageNumber==null) pageNumber=1;if(pageSize==null) pageNumber=10;//分页//Pageable是接口，PageRequest是接口实现，new PageRequest()是旧方法，PageRequest.of()是新方法//PageRequest.of的对象构造函数有多个，page是页数，初始值是0，size是查询结果的条数，后两个参数参考Sort对象的构造方法Pageable pageable = PageRequest.of(pageNumber,pageSize,Sort.Direction.DESC,"id");//Specification查询构造器Specification<Event> specification=new Specification<Event>() {private static final long serialVersionUID = 1L;@Overridepublic Predicate toPredicate(Root<Event> root, CriteriaQuery<?> query, CriteriaBuilder criteriaBuilder) {Predicate condition1 = null;if(StringUtils.isNotBlank(eventTitle)) {condition1 = criteriaBuilder.like(root.get("eventTitle"),"%"+eventTitle+"%");}else {condition1 = criteriaBuilder.like(root.get("eventTitle"),"%%");}Predicate condition2 = null;if(registerTime!=null) {condition2 = criteriaBuilder.greaterThan(root.get("registerTime"), registerTime);}else {condition2 = criteriaBuilder.greaterThan(root.get("registerTime"), new Timestamp(1514736000000L));}//Predicate conditionX=criteriaBuilder.and(condition1,condition2);//query.where(conditionX);query.where(condition1,condition2);//query.where(getPredicates(condition1,condition2)); //这里可以设置任意条查询条件return null;  //这种方式使用JPA的API设置了查询条件，所以不需要再返回查询条件Predicate给Spring Data Jpa，故最后return null}};Page<Event> list=eventRepository.findAll(specification, pageable);return ApiReturnUtil.page(list);}

ApiReturnUtil.page封装

其实这个大家根据自己的项目自己封装,这部分不作为核心内容,知识之前有部分网友比较纠结这个工具,所以简单放出来参考一下.

 public static ApiReturnObject page(Page returnObject) {return new ApiReturnObject(returnObject.getNumber()+"",returnObject.getNumberOfElements()+"",returnObject.getTotalElements()+"",returnObject.getTotalPages()+"","00","success",returnObject.getContent());   }

ApiReturnObject的主要内容:

 String errorCode="00";Object errorMessage;Object returnObject;String pageNumber;String pageSize;String totalElements;String totalPages;public ApiReturnObject(String pageNumber,String pageSize,String totalElements,String totalPages,String errorCode, Object errorMessage, Object returnObject) {super();this.pageNumber = pageNumber;this.errorCode = errorCode;this.errorMessage = errorMessage;this.returnObject = returnObject;this.pageSize = pageSize;this.totalElements = totalElements;this.totalPages = totalPages;}

查询效果

返回对象有用的是pageNumber、pageSize、totalElements、totalPages等属性，可对其进行封装

{"errorCode": "00","errorMessage": "success","pageNumber": "1","pageSize": "2","returnObject": [{"eventTitle": "1111","id": 3,"registerTime": 1528702813000,"status": "0"},{"eventTitle": "小明失踪","id": 2,"registerTime": 1526268436000,"status": "0"}],"totalElements": "5","totalPages": "3"
}

可以查询了。网上关于这个的资料也很少。希望可以帮到大家。

可能遇到的错误

Unable to locate Attribute  with the the given name [event] on this ManagedType [org.microservice.tcbj.yytsg.checkcentersys.entity.Event]

出现这样的情况，一般是因为实体类中没有这个属性，例如我Event的是eventTitle，写成了event，就会报错。

JpaSpecificationExecutor接口

20200114补充
JPA 提供动态接口JpaSpecificationExecutor，利用类型检查的方式，利用Specification进行复杂的条件查询，比自己写 SQL 更加便捷和安全.

public interface JpaSpecificationExecutor<T> {/*** Returns a single entity matching the given {@link Specification}.* * @param spec* @return*/T findOne(Specification<T> spec);/*** Returns all entities matching the given {@link Specification}.* * @param spec* @return*/List<T> findAll(Specification<T> spec);/*** Returns a {@link Page} of entities matching the given {@link Specification}.* * @param spec* @param pageable* @return*/Page<T> findAll(Specification<T> spec, Pageable pageable);/*** Returns all entities matching the given {@link Specification} and {@link Sort}.* * @param spec* @param sort* @return*/List<T> findAll(Specification<T> spec, Sort sort);/*** Returns the number of instances that the given {@link Specification} will return.* * @param spec the {@link Specification} to count instances for* @return the number of instances*/long count(Specification<T> spec);
}

Specification

Specification是我们传入进去的查询参数，是一个接口，并且只有一个方法

public interface Specification<T> {Predicate toPredicate(Root<T> root, CriteriaQuery<?> query, CriteriaBuilder cb);
}

一个一目了然的方法

第二个实现思路,听说这个方法已经过时了,其实这个方法是最好理解的.这里附上作为思路参考.

public Page<Even> findAll(SearchEven even) {Specification<Even> specification = new Specifications<Even>().eq(StringUtils.isNotBlank(even.getId()), "id", even.getId()).gt(Objects.nonNull(even.getStatus()), "status", 0).between("registerTime", new Range<>(new Date()-1, new Date())).like("eventTitle", "%"+even.getEventTitle+"%").build();return personRepository.findAll(specification, new PageRequest(0, 15));
}

Criteria+TypedQuery

思路三,利用EntityManager相关的CriteriaBuilder +CriteriaQuery+Predicate+TypedQuery进行查询.

@PersistenceContext
private EntityManager em;/*** CriteriaBuilder 安全查询创建工厂,创建CriteriaQuery,创建查询具体具体条件Predicate* @author zhengkai.blog.csdn.net*/
@Override
public List<Even> list(Even even) {//查询工厂CriteriaBuilder cb = em.getCriteriaBuilder();//查询类CriteriaQuery<Even> query = cb.createQuery(Even.class);//查询条件List<Predicate> predicates = new LinkedList<>();//查询条件设置predicates.add(cb.equal("id", even.getId()));predicates.add(cb.like("eventTitle", even.getEventTitle()));//拼接where查询query.where(cb.or(predicates.toArray(new Predicate[predicates.size()])));//用JPA 2.0的TypedQuery进行查询TypedQuery<Even> typedQuery = em.createQuery(query);return typedQuery.getResultList();
}