EclipseLink-查詢准備失敗，發生意外錯誤

Question

執行命令時，EntityManager拋出（所有https://pastebin.com/zKYBhsv8 ）

[EL Warning]: 2017-10-14 20:07:55.332--UnitOfWork(402037615)--Exception [EclipseLink-6168] (Eclipse Persistence Services - 2.7.0.v20170811-d680af5): org.eclipse.persistence.exceptions.QueryException
Exception Description: Query failed to prepare, unexpected error occurred: [java.lang.NullPointerException].
Internal Exception: java.lang.NullPointerException
Query: ReportQuery(referenceClass=MovieEntity )

代碼看起來像這樣

我創造

final CriteriaBuilder cb = this.entityManager.getCriteriaBuilder();
final CriteriaQuery<Long> countQuery = cb.createQuery(Long.class);
final Root<MovieEntity> root = countQuery.from(MovieEntity.class);

然后我創建謂詞

final Predicate whereClause = MovieSpecs
            .getFindPredicate(root, cb, countries);

這是方法

public static Predicate getFindPredicate(
        final Root<MovieEntity> root,
        final CriteriaBuilder cb
        final List<CountryType> countries
) {
    final List<Predicate> predicates = new ArrayList<>();
    if(countries != null && !countries.isEmpty()) {
        final List<Predicate> orPredicates =
                countries
                        .stream()
                        .map(status -> cb.equal(root.get(MovieEntity_.countries), countries))
                        .collect(Collectors.toList());
        predicates.add(cb.or(orPredicates.toArray(new Predicate[orPredicates.size()])));
    }
    return cb.and(predicates.toArray(new Predicate[predicates.size()]));
}

然后在countQuery中設置謂詞

countQuery.select(cb.count(root)).where(whereClause);

並執行命令

final Long count = this.entityManager.createQuery(countQuery).getSingleResult();

在這里我拋出了以上錯誤。

MovieEntity： https ://pastebin.com/CvhEQFZD MovieEntity_：http s：//pastebin.com/ZyJL0nmM

Answer 1

我認為當EclipseLink嘗試處理與集合匹配的countries匹配時，就會出現此問題：

.map(status -> cb.equal(root.get(MovieEntity_.countries), *countries*))

我認為您的意圖是檢查流項目是否相等

.map(status -> cb.equal(root.get(MovieEntity_.countries), status))

Answer 2

假設你希望所有MovieEntities有一個或多個提供的Countries ，你可以嘗試更換cb.equal(root.get(MovieEntity_.countries), countries)與cb.isMember(status, MovieEntity_.countries)

但是，這可能不是執行此操作的最佳方法，但至少最容易針對當前代碼進行測試。 也許您還應該將status更改為country以使代碼更易於理解。