英文:
Include only one property of nested object to toString method using Lombok
问题
我有以下情况：
@Data
public class Human {
private long id;
private Pet pet;
//其他属性...
}
@Data
public class Pet {
private long id;
private Human owner;
//其他属性...
}
我使用Lombok依赖项，当使用toString方法时，应用程序抛出java.lang.StackOverflowError异常。我知道我可以使用@ToString.Exclude来排除特定字段，但在这种情况下，我希望在toString方法中只显示嵌套对象的id属性。
换句话说，如果对象的toString方法调用其嵌套属性的toString方法，那么（仅在那种情况下）我希望只看到该对象的id。但如果我不是从父对象调用该对象的toString方法，我希望看到常规的toString。
我知道我可以自己定义toString、equals和hashCode方法来实现这一点，但是否可以告诉Lombok来完成这个任务？
英文:
i have a following case:
@Data
public class Human{
private long id;
private Pet pet;
//other properties...
}
@Data
public class Pet{
private long id;
private Human owner;
//other properties...
}
I use lombok dependency and when toString is used, application throws java.lang.StackOverflowError. I know I can use @ToString.Exclude to exclude given field, but in such case i would like to have only a nested object's id proeprty to be shown in a toString method.<br>
In other words, if an object's toString calls it's nested property toString, then (and only then) I want to see only that object id. But if i call that's object toString not from a parent object, I want to see a regular toString. <br>
I know that i can define toString, equals and hashCode methods by myself this way, but is this possible to tell lombok to do that?
答案1
得分: 2
一种方法是为宠物/主人的ID添加一个getter方法，并将其标记为@ToString.Include：
@Data
class Human{
private long id;
@ToString.Exclude
@EqualsAndHashCode.Exclude
private Pet pet;
@ToString.Include
public long petId() { return pet.getId(); }
//其他属性...
}
@Data
class Pet{
private long id;
@ToString.Exclude
@EqualsAndHashCode.Exclude
private Human owner;
@ToString.Include
public long ownerId() { return owner.getId(); }
}
用法:
var human = new Human();
var pet = new Pet();
human.setPet(pet);
pet.setOwner(human);
System.out.println(human);
// 输出:
// Human(id=0, petId=0)
注意，您可能还希望将pet和owner标记为@EqualsAndHashCode.Exclude，因为否则在某些情况下，equals和hashCode也可能导致堆栈溢出。
英文:
One way would be to add a getter for the pet/owner IDs, and mark that as @ToString.Include:
@Data
class Human{
private long id;
@ToString.Exclude
@EqualsAndHashCode.Exclude
private Pet pet;
@ToString.Include
public long petId() { return pet.getId(); }
//other properties...
}
@Data
class Pet{
private long id;
@ToString.Exclude
@EqualsAndHashCode.Exclude
private Human owner;
@ToString.Include
public long ownerId() { return owner.getId(); }
}
Usage:
var human = new Human();
var pet = new Pet();
human.setPet(pet);
pet.setOwner(human);
System.out.println(human);
// Output:
// Human(id=0, petId=0)
Note that you might also want to mark pet and owner as @EqualsAndHashCode.Exclude, because otherwise equals and hashCode might also cause stack overflows in some situations.
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