Spring Data -Specification用法和常用查询方法（in，join，equal等）
前言
在这一年里技术更新，从使用Mybatis转为Spring Data,总体感受是终于不用在自己写映射了，也可以少写方法和对应字段了。接下来总结在工作中常用的查询方式和方法，例如equal，join,in等。积少成多，在这里只收藏了用过查询与方法（如果方法可以用得更有，有更多的用法和不足之处请联系我）。
入门例子
controller层，这里是个简单查询获取所有用户并分页
@GetMapping("/list")
@ApiOperation(value = "所有用户列表")
public Result list(@RequestParam Map<String, Object> params) {
Page page = userService.queryPage(params);
return Result.ok().put("page", page);
}接下对service层的实现,功能是实现关键字搜索，这里因为简单并没有单独将Specification提出来，主要是对Specification接口有个大概的认识。
@Override
public page queryPage(Map<String, Object> params) {
//MapUtils方法用来取除params中的方法，来自于 org.apache.commons.collections.MapUtils;
String keyword = MapUtils.getSrting(params,"keyword");
Page page = sysUserRepository.findAll(new Specification<SysUserEntity>() {
@Override
public Predicate toPredicate(Root<SysUserEntity> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder) {
List<Predicate> predicates = new ArrayList<>();
if (StringUtils.isNotBlank(keyword)) {
List<Predicate> temp = new ArrayList<>();
for (String oneKeyword : keywordCopyStr) {
temp.add(criteriaBuilder.like(root.<String>get("mobile"), "%" + oneKeyword + "%"));
temp.add(criteriaBuilder.like(root.<String>get("trueName"), "%" + oneKeyword + "%"));
}
predicates.add(criteriaBuilder.or(temp.toArray(new Predicate[temp.size()])));
}
return criteriaQuery.where(predicates.toArray(new Predicate[predicates.size()])).getRestriction();
}
});
return page;
}Repository层中为了支持这样的查询，sysUserRepository需要继承JpaRepository（基本查询），JpaSpecificationExecutor（分页），这个接口是不需要再去实现的，到了Repository层就行，再对此进行扩充（比Mybatis简单多了）。
public interface sysUserRepository extends JpaRepository<SysCaptchaEntity, String>, JpaSpecificationExecutor<SysCaptchaEntity> {}Repository层常用写法
- 按着类字段查询 按着类关系关联查询不需要写语句的查询就不在详细讲解，给个例子看看就行
//查询第一个
EngineerVersionControl findTopByProjectIdAndOldOrderByVersionDesc(String projectId, int old);
//查询存在
boolean existsByProjectId(String projectId);
//排序
List<EngineerVersionControl> findByProjectIdOrderByVersionDesc(String projectId);- @Query语句查询
一般不会做物理删除，而是逻辑删除。保存操作使用save或者saveAll方法
//更新 必有@Modifying，和使用hiberna一样，HQL语句的写法
@Transactional(rollbackFor = Exception.class)
@Modifying
@Query("update SysUserEntity u set u.isDelete = ?2 ,u.gmtModified= ?3 where u.id = ?1 ")
int deleteIsUpdate(String id, int deleted, Date date);//查询
@Query("select u from SysUserEntity u where u.id in ?1 and u.isDelete = 0 ")
Page<SysUserEntity> findAllUser(List<String> userIds, Pageable pageable);//多表查询
@Query(value = " select p from DictionaryEntity p , DictionaryContentEntity w " +
" Where w.ContentEntity.id = ?1 and p.id = w.DictionaryEntity.id and p.deleted = ?2 ORDER BY p.dictionary")
List<WebsiteDictionaryEntity> webOnwDictionary(String id,int isDeleted);3.使用@Query实现写sql语句的查询
再spring data 中不仅有HQl语句，在功能太复杂的时候，可以使用sql语句进行本地查询
@Query(value="select serve.* from service_serve serve " +
"left join company_info_user cominfo on serve.company_info_user_id=cominfo.company_info_user_id" +
" left join user_company company on cominfo.company_info_user_id=company.company_info_user_id " +
" left join employee employeeen3_ on company.user_company_id=employeeen3_.user_company_id " +
" left join user userentity4_ on employeeen3_.user_id=userentity4_.user_id " +
" where userentity4_.user_id=?1 and employeeen3_.activity_management_power=1" +
" order by serve.gmt_create desc " +
"limit ?2 , ?3 " ,nativeQuery = true)
List<ServiceServeEntity> queryByCompany(String userId,int startPoint,int endPoint);4.@Param（value = “name”）查询，这是两种写法。一种?，一种@Param()
@Query(value="select activity.* from service_activity activity " +
"left join company_info_user cominfo on activity.company_id=cominfo.company_info_user_id" +
" left join user_company company on cominfo.company_info_user_id=company.company_info_user_id " +
" left join employee employeeen3_ on company.user_company_id=employeeen3_.user_company_id " +
" left join user userentity4_ on employeeen3_.user_id=userentity4_.user_id " +
" where userentity4_.user_id=:userId and employeeen3_.service_management_power=1 and activity.status=:status" +
" order by activity.gmt_create desc " +
"limit :startPoint , :endPoint " ,nativeQuery = true)
List<ServiceActivityEntity> queryByCompanyAndStatus(@Param(value="userId")String userId,@Param(value="status")int status, @Param(value="startPoint")int startPoint, @Param(value="endPoint")int endPoint);Specification 的用法
下面是个较为全面的例子，将一个较为复杂的查询提取成一个方法。这个方法时使用and的方式拼接，接下来的每一个查询都需要使用把finalConditions拼上，如同 finalConditions = criteriaBuilder.and(finalConditions, taskFastPre)。
public class TaskProjectSpecs {
public static Specification<Task> where(Map params, String userId, List<String> taskIds) {
//lambda表达式
return (Root<Task> root, CriteriaQuery<?> query, CriteriaBuilder criteriaBuilder) -> {
//开始
Predicate finalConditions = criteriaBuilder.conjunction();//提取参数
String taskFast = MapUtils.getString(params, "taskFast"); //lile 和join 用法 join可跟,JoinType.LEFT等
if (StringUtils.isNotBlank(taskFast)) {
Predicate taskFastPre = criteriaBuilder.like(root.join("taskType",JoinType.LEFT).<String>get("id"), "%" + taskFast + "%");
finalConditions = criteriaBuilder.and(finalConditions, taskFastPre);
}
//between用法
if ((null != createBegin) && (null != createEnd)) {
Predicate datePredicate = null;
if (createBegin.after(createEnd)) {
datePredicate = criteriaBuilder.between(root.get("gmtCreate"), createEnd, createBegin);
} else {
datePredicate = criteriaBuilder.between(root.get("gmtCreate"), createBegin, createEnd);
}
finalConditions = criteriaBuilder.and(finalConditions, datePredicate);
}
//equale
if (null != emergency && 0 != emergency) {
finalConditions = criteriaBuilder.and(finalConditions, criteriaBuilder.equal(root.get("emergencyLevel"), emergency));
}
//大于 不等于
if (status != null) {
finalConditions = criteriaBuilder.and(finalConditions, criteriaBuilder.greaterThan(root.get("startDate"), new Date()));
finalConditions = criteriaBuilder.and(finalConditions, criteriaBuilder.notEqual(root.get("status"), 1)); }
// or
if (StringUtils.isNotBlank(keyword)) {
finalConditions = criteriaBuilder.and(finalConditions, criteriaBuilder.or(
criteriaBuilder.like(root.get("taskName"), "%" + keyword + "%"),
criteriaBuilder.like(root.join("project").get("name"), "%" + keyword + "%"))
);
}
//in
if (taskIds.size() > 0) {
CriteriaBuilder.In<Object> in = criteriaBuilder.in(root.get("id"));
for (String id : taskIds) {
in.value(id);
}
finalConditions = criteriaBuilder.and(finalConditions, in);
}
return query.where(finalConditions).getRestriction();
};
}}
上面的方法是and凭借，还有一种add的方法，本质一样，都是构建query.where（）查询。
public class UserSpecs {
public static Specification<SysUserEntity> where(String keyword, Date createdAtBegin, Date createdAtEnd, List<String> userIds) {
return (Root<SysUserEntity> root, CriteriaQuery<?> query, CriteriaBuilder cb) -> {
List<Predicate> predicates = new ArrayList<>();
if (StringUtils.isNotBlank(keyword)) {
List<Predicate> temp = new ArrayList<>();
Set<String> keywordCopyStr = StringUtil.cutToArray(keyword);
for (String oneKeyword : keywordCopyStr) {
temp.add(cb.like(root.<String>get("mobile"), "%" + oneKeyword + "%"));
temp.add(cb.like(root.<String>get("trueName"), "%" + oneKeyword + "%"));
}
predicates.add(cb.or(temp.toArray(new Predicate[temp.size()])));
}
//未删除
predicates.add(cb.equal(root.get("isDelete"), Constant.NOT_DELETED));
query.where(predicates.toArray(new Predicate[predicates.size()]));
return query.getRestriction();
};
}
}
return query.where(predicates.toArray(new Predicate[predicates.size()])).getRestriction();总结
基本将常用的都包含完了，以后遇到了新的写法再更新上去。
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