如何从HQL查询创建谓词? [英] How can I create a Predicate from a HQL query?

问题描述

我有这个存储库:

@Repository
public interface UserRepository extends
        JpaRepository<User, String>,
        JpaSpecificationExecutor<User> {

    @Query("select u from User u, UserRole ur " +
            "where u.dep = ur.dep " +
            "and u.allowed = 1")
    List<User> getAllowed();

}

但是我想通过自定义Spring Data Specification更改@Query，以便像这样调用它:

But I want to change the @Query by a custom Spring Data Specification, in order to call it like:

repository.findAll(new Allowed());

所以我已经将extends JpSpecificationExecutor<User>添加到我的存储库中，现在我正在尝试创建Specification实现:

So I have added extends JpSpecificationExecutor<User> to my repository and now I'm trying to create the Specification implementation:

public class Allowed implements Specification<User> {
    @Override
    public Predicate toPredicate(Root<User> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
      //??
    }
}

如何将上面的查询转换为谓词?如何使用UserRole实体执行联接?

How can I convert the query above to a Predicate? How can I perform the join with UserRole entity?

推荐答案

创建一个创建并返回规范的类，其好处是该类可以根据各种情况返回单独的规范.

Create a class which creates and returns specification, its benefit is that this class can return separate specifications based on various situations.

@Component
public class UserSpecification {
    public Specification<User> getAllowedUserSpecification() {
        return new Specification<User>() {

            @Override
            public Predicate toPredicate(Root<User> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
                Predicate predicate = cb.equal(root.get("allowed"), "1");
                return predicate;
            }
        };
    }
}

然后在Service类中只是将上面的类自动接线并像下面那样使用

Then in Service class just autowire the above class and use it like below

repo.findAll(userSpecification.getAllowedUserSpecification());

规范中不需要用户和用户角色的联接，因为在创建实体类时必须设置关系.

The join of User and UserRole is not required in specification because you have to set relationship while creating the entity class.

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