spring-data-jpa Specification构建动态sql

1.持久层继承JpaSpecificationExecutor

@Repository
public interface DailyBillingRepository extends PagingAndSortingRepository, JpaSpecificationExecutor {


}

2.JpaSpecificationExecutor 提供的方法： 

public interface JpaSpecificationExecutor {
 
    T findOne(Specification spec);
 
    List findAll(Specification spec);
 
    Page findAll(Specification spec, Pageable pageable);
 
    List findAll(Specification spec, Sort sort);
 
    long count(Specification spec);
}

调用 ：

 public Page getList(Integer page, Integer rows,String beginTime,String endTime,String result){
        //Specification创建动态sql
        //Root root, CriteriaQuery criteriaQuery, CriteriaBuilder criteriaBuilder
        Specification specification= (root, query, cb) -> {
            Predicate predicate = cb.conjunction();

            if (StringHelper.isNotBlank(beginTime) && StringHelper.isNotBlank(endTime)){
                // sql ==》 billData between beginTime and endTime
                predicate.getExpressions().add(
                        cb.between(root.get("billData"), DateHelper.getDate(beginTime), DateHelper.getDate(endTime))
                );
            }

            if (StringHelper.isNotBlank(result) && !result.equals("2")){
                // sql ==》 differenceAmount = 0  或者 differenceAmount <> 0
                Predicate p = null;
                if ("1".equals(result)){
                    p = cb.equal(root.get("differenceAmount"),BigDecimal.ZERO);
                }
                if ("0".equals(result)){
                    p = cb.notEqual(root.get("differenceAmount"),BigDecimal.ZERO);
                }
                predicate.getExpressions().add(p);
            }
            return predicate;
        };

        return dailyBillingRepository.findAll(specification,new PageRequest(page,rows));
    }

CriteriaBuilder接口提供了操作sql的基本语句，可直接调用。