在equals和hashCode中说明hasMany关系 [英] Account for hasMany relationships in equals and hashCode

问题描述

我想使用 @EqualsAndHashCode 我的域类上的注释，但似乎该注释生成的equals和hashCode方法没有考虑hasMany字段.我看不到有任何方法可以通过注释来更改它，但是我希望我缺少一些东西，因为它非常方便(如果可以的话).

I would like to use the @EqualsAndHashCode annotation on my domain classes, but it seems the equals and hashCode methods generated by that annotation don't take hasMany fields into account. I don't see any way to change this with the annotation, but I'm hoping that I'm missing something because it is very convenient (if it works).

推荐答案

• 在父域类中将hasMany关系定义为Set，我们通常不这样做，因为它是多余的.
• 您还必须确保对子域使用@EqualsAndHashCode AST.
• Define the hasMany relationship as a Set in the parent domain class, which we normally do not do as it is redundant.
• You also have to make sure you are using @EqualsAndHashCode AST for the child domain.

例如:

import groovy.transform.EqualsAndHashCode
@EqualsAndHashCode
class Parent {
    String name
    Integer age

    //Adding this as a property makes it a candidate for equals() and hashCode()
    Set<Child> children

    static hasMany = [children: Child]
}

@EqualsAndHashCode
class Child {
    String name
    static belongsTo = [parent : Parent]
}

//Unit Test
void testSomething() {
    def parent1 = new Parent(name: 'Test', age: 20).save()
    def child1 = new Child(name: 'Child1')
    parent1.addToChildren(child1)
    parent1.save()

    def parent2 = new Parent(name: 'Test', age: 20).save()
    def child2 = new Child(name: 'Child1')
    parent2.addToChildren(child2)
    parent2.save(flush: true)

    assert parent1 == parent2
    assert child1 == child2
}

以防万一，您正在考虑索引hasMany项，然后使用List而不是Set.

In case, you are thinking of indexing hasMany items, then use List instead of Set.

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