JPA：没有@OneTomany注释的左联接

Question

@Entity
@Table(name = "my_table")
public class MyTable {

    @Id
    @Column(name = "id", nullable = false, unique = true)
    private Integer id;

    @Transient
    private String lang;

    @Transient
    private String text;

    // getters and setters
    ...
}

@Entity
@Table(name = "my_table_translation")
public class MyTableTranslation {

    @Id
    @Column(name = "id", nullable = false, unique = false)
    private Integer id;

    @Id
    @Column(name = "lang", nullable = false, unique = false, length = 2)
    private String lang;

    @Column(name = "text", nullable = false, unique = false, length = 200)
    private String text;

    // getters and setters
    ...
}

public void findAll(String language) {
    List<MyTable> list = repository.findAll(new Specification<MyTable>() {
        @Override
        public Predicate toPredicate(Root<MyTable> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
            // something there
            return ...;
        }
    });
}

SELECT t1, t2 FROM MyTable t1 LEFT JOIN MyTableTranslation t2 ON t1.id = t2.id

我想它不干净...有没有人知道如何在不使用SQL符号的情况下使它变得简单？

Answer 1

我尝试使用@OneTomany注释，我更改了我的DTO：

@Entity
@Table(name = "my_table")
public class MyTable {

    @Id
    @Column(name = "id", nullable = false, unique = true)
    private Integer id;

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    @JoinColumn(name = "id", referencedColumnName = "id")
    private List<MyTableTranslation> translations = new ArrayList<MyTableTranslation>();

    // getters and setters
    ...
}

并将标准更改为：

public void findAll(String isolang) {
    List<MyTable> list = repository.findAll(new Specification<MyTable>() {
        @Override
        public Predicate toPredicate(Root<MyTable> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
            Join<Object, Object> langJoin = root.join("translations", JoinType.LEFT);
            return cb.equal(langJoin.get("lang"), isolang);
        }
    });
}

但列表中没有项目。如果我将FetchType更改为EAGER，谓词没有效果，我将得到所有的语言。我不知道现在该怎么继续...