jpa多条件查询

首先继承JpaSpecificationExecutor<T>接口

需要用到JpaSpecificationExecutor<T>中的Page<T> findAll(@Nullable Specification<T> spec, Pageable pageable);//多条件分页查询

ITpSamplerInfoService.java

Page<TpSamplerInfo> findByConditionPage(Long samplerCode,String crossName,Pageable pageable);

TpSamplerInfoServiceImpl.java实现类

@Autowired
ITpSamplerInfoDao samplerInfoDao;//继承JpaSpecificationExecutor<T>

@Override
	public Page<TpSamplerInfo> findByConditionPage(Long samplerCode,String crossName, Pageable pageable) {
		Page<TpSamplerInfo> pageList = samplerInfoDao.findAll(new Specification<TpSamplerInfo>() {
			@Override
			public Predicate toPredicate(Root<TpSamplerInfo> root, CriteriaQuery<?> query,
					CriteriaBuilder criteriaBuilder) {
				List<Predicate> list = new ArrayList<Predicate>();
				if(samplerCode!=null) {
					list.add(criteriaBuilder.like(root.get("samplerCode"), "%"+samplerCode+"%"));
				}
				if(crossName!=null) {
					//外键对象的属性，要用join再get
					list.add(criteriaBuilder.like(root.join("tpCrossroadInfo").get("crssroadName"), crossName));
				}
				Predicate[] array = new Predicate[list.size()];
                return criteriaBuilder.and(list.toArray(array));
			}
		},pageable);
		return pageList;
	}

//例子2，查询时间段内的记录
@Override
	public Page<MapPack> findAll(Integer code, String startData, String endData, Pageable pageable) {
		Page<MapPack> pageList = getMapPackDao().findAll(new Specification<MapPack>() {

			@Override
			public Predicate toPredicate(Root<MapPack> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
				List<Predicate> list = new ArrayList<Predicate>();

				SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
				SimpleDateFormat sdfmat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

				if (StringUtils.isNotEmpty(startData) && StringUtils.isNotEmpty(endData)) {
			        try {
						list.add(cb.between(root.get("registerTime"),
								sdfmat.parse(sdfmat.format(sdf.parse(startData).getTime())),
	                            sdfmat.parse(sdfmat.format(sdf.parse(endData).getTime() + 86400000))));
					} catch (ParseException e) {
						e.printStackTrace();
					}
			    }
				if(code!=-1) {
					list.add(cb.equal(root.join("city").get("id").as(String.class), code));
				}
				Predicate[] array = new Predicate[list.size()];
                return cb.and(list.toArray(array));
			}
		}, pageable);
		return pageList;
	}

　　

　　

　controller

@RequestMapping("/getAllSamplerInfo")
    public Map<String,Object> findByConditionPage(@RequestParam("pageNumber") int page,@RequestParam("pageSize") int size,
            @RequestParam("samplerCode") Long samplerCode,@RequestParam("crossName") String crossName){
        Map<String,Object> map = new HashMap<String, Object>();
        Pageable pageable = PageRequest.of(page-1, size, Direction.DESC, "id");
        Page<TpSamplerInfo> pageList = tpSamplerInfoService.findByConditionPage(samplerCode,crossName, pageable);
        //使用值对象Vo包装一下实体类，解决递归问题
        List<TpSamplerInfoVo> list = new ArrayList<>();
        pageList.forEach(pl->{
            TpSamplerInfoVo tpVo = new TpSamplerInfoVo(pl);
            list.add(tpVo);
        });
        map.put("rows", list);
        map.put("total", pageList.getTotalElements());

        return map;

    }

注意：在多条件查询时候查询id主键的时候遇到过一个错误

Parameter value [%3%] did not match expected type [java.lang.Long (n/a)]      意思是参数不匹配预期类型，id是Long类型

解决办法：list.add(criteriaBuilder.like(root.get("id").as(String.class), "%"+crossId+"%"));

加上as(String.class)就不会出现类型不匹配的问题