GSON：如何在保留循环引用的同时防止StackOverflowError？

问题描述

我有一个循环引用的结构。
为了调试目的，我想转储它。基本上就是任何格式，但我选择了JSON。

因为它可以是任何类，所以我选择了不需要JAXB注释的GSON。

但是GSON命中循环引用并递归，直到 StackOverflowError 。

我该如何将GSON限制为

• 忽略某些类成员？
  不符合 @XmlTransient 和 @JsonIgnore 。




• 忽略某些对象图路径？例如。我可以指示GSON不要序列化 release.customFields.product 。




• 最高2级？

相关：

解决方案

简单地设置字段transient（如 private transient int field = 4; ）。 GSON了解这一点。

编辑

无需内置注释; Gson让你插入你自己的战略，排除领域和类。它们不能基于路径或嵌套级别，但注释和名称很好。

如果我想跳过类my.model.Person上名为lastName的字段，我可以写下如下的排除策略：

  class MyExclusionStrategy实现了ExclusionStrategy {
 
 public boolean shouldSkipField（FieldAttributes fa）{
 String className = fa。 。getDeclaringClass（）的getName（）; 
 String fieldName = fa.getName（）; 
返回
 className.equals（my.model.Person）
&& fieldName.equals（ 姓氏）; 
 
 $ b @Override 
 public boolean shouldSkipClass（Class<？> type）{
 //永远不会跳过任何类
 return false; 
 
 
  

我也可以创建自己的注释：

  @Retention（RetentionPolicy.RUNTIME）
 public @interface GsonRepellent {
 
} 
  

然后将 shouldSkipField 方法重写为：

  public boolean shouldSkipField（FieldAttributes fa）{
 return fa.getAnnotation（GsonRepellent.class）！= null; 
} 
  

这可以让我做这样的事情：

  public class Person {
 @GsonRepellent 
 private String lastName =Troscianko; 
 
 // ... 
  

要使用自定义ExclusionStrategy，请构建Gson使用构建器的对象：

$ pre $ g $ gson new GsonBuilder
setsettingStrategies（new MyOwnExclusionStrategy（））
.create（）;

I have a structure with circular references.And for debug purposes, I want to dump it. Basically as any format, but I chose JSON.

Since it can be any class, I chose GSON which doesn't needs JAXB annotations.

But GSON hits the circular references and recurses until StackOverflowError.

How can I limit GSON to

• ignore certain class members?Both @XmlTransient and @JsonIgnore are not obeyed.

• ignore certain object graph paths? E.g. I could instruct GSON not to serialize release.customFields.product.

• go to the depth of at most 2 levels?

Related: Gson.toJson gives StackOverFlowError, how to get proper json in this case? (public static class)

解决方案

Simply make the fields transient (as in private transient int field = 4;). GSON understands that.

Edit

No need for a built-in annotation; Gson lets you plug in your own strategies for excluding fields and classes. They cannot be based on a path or nesting level, but annotations and names are fine.

If I wanted to skip fields that are named "lastName" on class "my.model.Person", I could write an exclusion strategy like this:

class MyExclusionStrategy implements ExclusionStrategy {

    public boolean shouldSkipField(FieldAttributes fa) {
        String className = fa.getDeclaringClass().getName();
        String fieldName = fa.getName();
        return
            className.equals("my.model.Person")
                && fieldName.equals("lastName");
    }

    @Override
    public boolean shouldSkipClass(Class<?> type) {
        // never skips any class
        return false;
    }
}

I could also make my own annotation:

@Retention(RetentionPolicy.RUNTIME)
public @interface GsonRepellent {

}

And rewrite the shouldSkipField method as:

public boolean shouldSkipField(FieldAttributes fa) {
    return fa.getAnnotation(GsonRepellent.class) != null;
}

This would enable me to do things like:

public class Person {
    @GsonRepellent
    private String lastName = "Troscianko";

    // ...

To use a custom ExclusionStrategy, build Gson object using the builder:

Gson g = new GsonBuilder()
       .setExclusionStrategies(new MyOwnExclusionStrategy())
       .create();

这篇关于GSON：如何在保留循环引用的同时防止StackOverflowError？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！