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java - Java：使用标准创建内部联接

问题描述

我很难寻找有关如何使用内部联接创建条件查询的好示例。我已经创建了下面的查询，这将是我想要对条件执行的操作。

SELECT DISTINCT *
FROM DT_DOCUMENT as document 
INNER JOIN DT_TRANSLATION as translation
ON translation.language_id IN(1, 2, 3) 
WHERE document.id = translation.document_id
AND document.title LIKE '%Document%';

返回标题为 Document 的所有文档以及 ID 为 1,2 和 3 的翻译。

我能够使用标准创建 2 个不同的选择，但我无法在这些表之间生成内部连接以统一代码。

翻译条件查询

CriteriaQuery<Translation> translationQuery = builder.createQuery(Translation.class);
Root<Translation> translation = translationQuery.from(Translation.class);

List<Long> ids = new ArrayList<>();
ids.add(1);
ids.add(2);
ids.add(3);
Predicate idPredicate = translation.in(ids);
translationQuery.where(idPredicate);
translationQuery.distinct(true);

TypedQuery<Translation> query = this.entityManager.createQuery(translationQuery);
query.getResultList();

返回 id 为 1,2 和 3 的所有翻译；

单据条件查询

CriteriaQuery<Document> documentQuery = builder.createQuery(Document.class);
Root<Document> document = documentQuery.from(Document.class);

Predicate titlePredicate = builder.like(document.get("title"), "%Document%");
documentQuery.where(titlePredicate);
TypedQuery<Document> query = this.entityManager.createQuery(documentQuery);
query.getResultList();

返回所有标题为 Document 的文件。

任何提示？谢谢。

标签： javasqlcriteriacriteria-api

解决方案

经过长时间的搜索，我提出了这个解决方案，统一了 2 个查询并使用了内部连接：

    //query creation
    CriteriaBuilder builder = entityManager.getCriteriaBuilder();
    CriteriaQuery<Document> documentQuery = builder.createQuery(Document.class);
    Root<Document> root = documentQuery.from(Document.class);

    //parameter list for where
    List<Predicate> predicateList = new ArrayList<Predicate>();

    //doing the join: pass the translations reference (list <Translations) that exists in the document model.
    Join<Document, Translation> documentTranslationJoin = root.join("translations");
   //I get the ids of the languages ​​associated with the translations found in the join
    Path<Long> translationLanguageId = documentTranslationJoin.get("language");
    //I passed the ids of the languages ​​that I want to find translations
    List<Long> ids = new ArrayList<>();
    ids.add(1);
    ids.add(2);
    ids.add(3);

    //considers languages ​​of translations
    Predicate predicateTranslationId = builder.isTrue(translationLanguageId.in(ids));
    //I passed the ids of the languages ​​that will be the where looking for the translations that have the ids of the languages ​​that I want to see
    predicateList.add(predicateTranslationId);


    //considers title of document
    Predicate titlePredicate = builder.like(root.get("title"),"%documento%");
    predicateList.add(titlePredicate);

    //where
    Predicate[] predicates = new Predicate[predicateList.size()];
    predicateList.toArray(predicates);
    documentQuery.where(predicates);

    //execution of the query with its parameters
    TypedQuery<Document> query = this.entityManager.createQuery(documentQuery);

    query.setFirstResult(0);
    query.setMaxResults(8);

    //results
    List<Document> documents = query.getResultList();

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