小编CVV*_*CVV的帖子

这是我的repository界面:

public interface ContentRepository extends JpaRepository<Content, Long> {

    @Query(value = "select c from Content c where c.ContentCategory.genre =  :genre and c.ContentType.genre = :contentType")
    Iterable<Content> findByTypeAndCategory(@Param("contentType") String contentType, @Param("genre") String genre);

}

这是ContentPOJO:

@Entity
@Table(name = "content")
public class Content implements Serializable {

public Content() {
}

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private long id;

@ManyToOne
private ContentCategory contentCategory;

@ManyToOne
private ContentType contentType;

// other methods }

在这里我的applicationContext.xml:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xmlns:jpa="http://www.springframework.org/schema/data/jpa" …

我有一个包含作者列表的书类:

@Entity
@Table(name = "book")
public class Book extends Content {

    @ManyToMany(fetch = FetchType.LAZY)
    private List<Author> authors;
...}

现在,这是我的BookSpecifications班级:

public static Specification<Book> authorIdIs(Long authorId) {
    return new Specification<Book>() {
        @Override
        public Predicate toPredicate(Root<Book> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder cb) {
            return cb.isTrue(root.get("authors").get("id").in(authorId));
        }
    };
}

如何检查authorId列表中的给定内容？

错误:

java.lang.IllegalStateException: Illegal attempt to dereference path source [null.authors] of basic type
    at org.hibernate.jpa.criteria.path.AbstractPathImpl.illegalDereference(AbstractPathImpl.java:98) ~[hibernate-entitymanager-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.jpa.criteria.path.AbstractPathImpl.get(AbstractPathImpl.java:191) ~[hibernate-entitymanager-4.3.11.Final.jar:4.3.11.Final]
    at com.tarameshgroup.derakht.service.specs.BookSpecifications$3.toPredicate(BookSpecifications.java:40) ~[classes/:na]
    at org.springframework.data.jpa.domain.Specifications$ComposedSpecification.toPredicate(Specifications.java:189) ~[spring-data-jpa-1.9.2.RELEASE.jar:na]

我有两个简单的桌子content，contentType

@Entity
@Table(name = "content")
public class Content implements Serializable {

public Content() {}

public Content(String title, String description) {
    this.title = title;
    this.description = description;
}

@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE)
private long id;

@ManyToOne
private ContentCategory contentCategory;

@ManyToOne
private ContentType contentType;

 // getter/setters
}

@Entity
@Table(name = "contentType")
public class ContentType implements Serializable {

public ContentType() {}

public ContentType(String contentType) {
    this.contentType = contentType;
}

@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE)
private long id;

@NotNull
private String contentType; …