我想找到类A的所有对象(类A与类B具有多对多关系),这些对象中至少有一个B类对象集中的一个对象,并且在字段中具有某个值。
虽然我可以四处走动,但仍在互联网上搜索文档,尽管创建了摘要描述的发票清单,但我很好奇我是否能够使用纯规范进行书写。
@ManyToMany(mappedBy = "A.name")
public class A {
private Set<B> b;
}
@JoinTable(name = "AB",
joinColumns = {@JoinColumn(name = "B_id", referencedColumnName = "id")},
inverseJoinColumns ={@JoinColumn(name= "A_id",referencedColumnName="id")})
@ManyToMany(cascade = {CascadeType.PERSIST, CascadeType.MERGE})
public class B
{
private Object certainField;
private Set<A> a;
}
public static Specification<A> hasB(Set<B> b) {
return (a, cq, cb) -> {
//I want to find all the Objects<A> which have an Element B with
// CertainField.equals(aValue);
// I find it hard to understand the syntax and i find no clue how
// to
// make it work.
};
}