[英]JPA Criteria Join OneToMany table where clause does not work
我有两张桌子。
CREATE TABLE public.question
(
id SERIAL PRIMARY KEY
, day VARCHAR(2) NOT NULL
, month VARCHAR(2) NOT NULL
, year VARCHAR(4) NOT NULL
);
CREATE TABLE public.question_translation
(
id SERIAL PRIMARY KEY
, question_id INT REFERENCES public.question(id) NOT NULL
, question_text TEXT NOT NULL
, language VARCHAR(2) NOT NULL
);
现在我想创建检索问题的标准。 像这样的SQL:
SELECT * FROM question q LEFT JOIN question_translation qt ON q.id = qt.question_id WHERE qt.language = 'en'
在使用JPA Criterias的java中,它看起来像这样:
@Override
public Collection<Question> findByMonthYear(String month, String year, String locale) {
EntityManager em = sessionFactory.createEntityManager();
CriteriaBuilder builder = em.getCriteriaBuilder();
CriteriaQuery<Question> criteriaQuery = builder.createQuery(Question.class);
List<Predicate> predicates = new ArrayList<>();
Root<Question> questionRoot = criteriaQuery.from(Question.class);
ListJoin<Question, QuestionTranslation> questionTranslationJoinRoot = questionRoot.join(Question_.questionTranslation, JoinType.LEFT);
predicates.add(builder.equal(questionRoot.get(Question_.month), month));
predicates.add(builder.equal(questionRoot.get(Question_.year), year));
predicates.add(builder.equal(questionTranslationJoinRoot.get(QuestionTranslation_.language), locale));
criteriaQuery.select(questionRoot).where(predicates.toArray(new Predicate[]{}));
TypedQuery<Question> query = em.createQuery(criteriaQuery);
String queryString = query.unwrap(Query.class).getQueryString();
return query.getResultList();
}
我使用ListJoin,因为在metamodel Question_.class
我得到了这一行:
public static volatile ListAttribute<Question, QuestionTranslation> questionTranslation;
但是这个给我带有List QuestionTranslation的Question类,其中有两个条目,其中语言字段等于en
和de
值。 但我指定where子句只返回一个语言等于en
值的条目。 我的代码出了什么问题?
更新#1:
我有第二个案子。
还有一张桌子:
CREATE TABLE public.user_answer
(
uuid VARCHAR(36) PRIMARY KEY
, user_uuid VARCHAR(36) REFERENCES public.users(uuid) NOT NULL
, question_id INT REFERENCES public.question(id) NOT NULL
, answer TEXT NOT NULL
);
我想像这样制作SQL:
SELECT * FROM user_answer ua LEFT JOIN question q on ua.question_id = q.id LEFT JOIN question_translation qt ON q.id = qt.question_id WHERE qt.language = 'en' AND ua.user_uuid = '00000000-user-0000-0000-000000000001' AND q.month = '01' AND q.day = '01' AND q.year = '2016';
在使用JPA Criterias的java中,它看起来像这样:
@Override
public UserAnswer findByDayMonthYear(String day, String month, String year, User user, String locale) {
EntityManager em = sessionFactory.createEntityManager();
CriteriaBuilder builder = em.getCriteriaBuilder();
CriteriaQuery<UserAnswer> criteriaQuery = builder.createQuery(UserAnswer.class);
List<Predicate> predicates = new ArrayList<>();
Root<UserAnswer> userAnswerRoot = criteriaQuery.from(UserAnswer.class);
Join<UserAnswer, Question> questionJoin = userAnswerRoot.join(UserAnswer_.question);
ListJoin<Question, QuestionTranslation> questionTranslatJoin = questionJoin.join(Question_.questionTranslation);
predicates.add(builder.equal(builder.treat(questionJoin, Question.class).get(Question_.day), day));
predicates.add(builder.equal(builder.treat(questionJoin, Question.class).get(Question_.month), month));
predicates.add(builder.equal(builder.treat(questionJoin, Question.class).get(Question_.year), year));
predicates.add(builder.equal(builder.treat(questionTranslatJoin, QuestionTranslation.class).get(QuestionTranslation_.language), locale));
predicates.add(builder.equal(userAnswerRoot.get(UserAnswer_.user), user));
criteriaQuery.select(userAnswerRoot).where(predicates.toArray(new Predicate[]{}));
TypedQuery<UserAnswer> query = em.createQuery(criteriaQuery);
String queryString = query.unwrap(Query.class).getQueryString();
return query.getSingleResult();
}
在这种情况下,问题列表包含两个QuestionTranlsation项目,其中包含语言en
和de
,但我只需要一个QuestionTranlsation条目,其中语言等于en
。
在这种情况下我该怎么做?
这可以通过JPA 2.1功能JOIN ON
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