如何使用ctiteria API spring data JPA规范定义条件上的多连接？

Question

下面是fetch join的代码

public static Specification<Item> findByCustomer(User user) {
    return (root, criteriaQuery, criteriaBuilder) -> {
       root.fetch(User_.address, JoinType.LEFT);
        return criteriaBuilder.equal(root.get(User_.id), 1);
    };
}

上面的代码正在生成下面的查询

Answer 1

public static Specification<A> findAbyBname(String input) {
        return new Specification<A>() {
            @Override
            public Predicate toPredicate(Root<A> root, CriteriaQuery<?> cq, CriteriaBuilder cb) {
                cq.distinct(true);
                Join<A,AB> AjoinAB = root.joinList(A_.AB_LIST,JoinType.LEFT);
                Join<AB,B> ABjoinB = AjoinAB.join(AB_.B,JoinType.LEFT);
                return cb.equal(ABjoinB.get(B_.NAME),input);
            }
        };
    }

我有这样的东西。以下是实体：

@Entity
public class A {
    @Id
    private Long id;
    private String name;
    @OneToMany(mappedBy = "a")
    private List<AB> abList;
}
@Entity
public class B {
    @Id
    private Long id;
    private String name;
    @OneToMany(mappedBy = "b")
    private List<AB> abList;
}
@Entity
public class AB {
    @Id
    private Long id;
    private String name;
    @ManyToOne
    @JoinColumn(name = "a_id")
    private A a;
    @ManyToOne
    @JoinColumn(name = "b_id")
    private B b;
}