详解Spring Data JPA动态条件查询的写法

JpaSpecificationExecutor

public interface CustomerRepository extends CrudRepository<Customer, Long>, JpaSpecificationExecutor {
 …
}

public interface JpaSpecificationExecutor<T> {
 T findOne(Specification<T> var1);

 List<T> findAll(Specification<T> var1);

 Page<T> findAll(Specification<T> var1, Pageable var2);

 List<T> findAll(Specification<T> var1, Sort var2);

 long count(Specification<T> var1);
}

List<T> findAll(Specification<T> var1);

org.springframework.data.jpa.domain.Specification

Specification specification = new Specification() {
   @Override
   public Predicate toPredicate(Root root, CriteriaQuery criteriaQuery, CriteriaBuilder criteriaBuilder) {
    return null;
   }
  }

/**
 * A root type in the from clause.
 * Query roots always reference entities.
 *
 * @param <X> the entity type referenced by the root
 * @since Java Persistence 2.0
 */
public interface Root<X> extends From<X, X> {...}

/**
 * Used to construct criteria queries, compound selections,
 * expressions, predicates, orderings.
 *
 * <p> Note that <code>Predicate</code> is used instead of <code>Expression&#060;Boolean&#062;</code>
 * in this API in order to work around the fact that Java
 * generics are not compatible with varags.
 *
 * @since Java Persistence 2.0
 */
public interface CriteriaBuilder {...}

criteriaBuilder.lessThan(root.get("createDate"), today)

/**
  * Create a conjunction of the given restriction predicates.
  * A conjunction of zero predicates is true.
  *
  * @param restrictions zero or more restriction predicates
  *
  * @return and predicate
  */
 Predicate and(Predicate... restrictions);

/**
  * Create a disjunction of the given restriction predicates.
  * A disjunction of zero predicates is false.
  *
  * @param restrictions zero or more restriction predicates
  *
  * @return or predicate
  */
 Predicate or(Predicate... restrictions);

public List<WeChatGzUserInfoEntity> findByCondition(Date minDate, Date maxDate, String nickname){
  List<WeChatGzUserInfoEntity> resultList = null;
  Specification querySpecifi = new Specification<WeChatGzUserInfoEntity>() {
   @Override
   public Predicate toPredicate(Root<WeChatGzUserInfoEntity> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder) {

    List<Predicate> predicates = new ArrayList<>();
    if(null != minDate){
     predicates.add(criteriaBuilder.greaterThan(root.get("subscribeTime"), minDate));
    }
    if(null != maxDate){
     predicates.add(criteriaBuilder.lessThan(root.get("subscribeTime"), maxDate));
    }
    if(null != nickname){
     predicates.add(criteriaBuilder.like(root.get("nickname"), "%"+nickname+"%"));
    }
    return criteriaBuilder.and(predicates.toArray(new Predicate[predicates.size()]));
   }
  };
  resultList = this.weChatGzUserInfoRepository.findAll(querySpecifi);
  return resultList;
 }