我卡中的问题，我需要把我的对象的引用被解析使用反序列化过程中，其子对象 GSON 和 InstanceCreator 。

I'm stuck in a problem where I need to set reference of my object being parsed to its child objects during deserialization using Gson and InstanceCreator.

要描绘的问题，以下是类结构简单的重新presentation。

To depict the problem, following is the simple representation of classes' structure.

public class Workshift {
    private final transient Context context;
    private final Visit visit;

    public Workshift(Context context) {
        this.context = context;
        this.visit = new Visit(this);
    }
}

public class Visit {
    private final transient Workshift workshift;

    public Visit(Workshift ws) {
        this.workshift = ws;
    }
}

在这种结构下，我能够通过向设置在轮班 上下文的 InstanceCreator 我的 GsonBuilder ，例如：

Gson gson = new GsonBuilder()
    .registerTypeAdapter(Workshift.class, new InstanceCreator<Workshift>() {
        @Override
        public Workshift createInstance(Type type) {
            return new Workshift(context);
        }
    })
    .create();

我知道，我可以添加额外的 InstanceCreator 我的 GsonBuilder ，但我不知道如何提供我的轮班对象的引用是在被解析的处理（即时），以访问对象？

I know, I can add additional InstanceCreator to my GsonBuilder, but I'm not sure how to provide a reference of my Workshift object which is in the process of being parsed (on-the-fly) to Visit object?

任何帮助将是AP preciated！

Any help would be appreciated!

推荐答案

您一定要使用 GraphAdapterBuilder 。

正如你在下面@Braj的答案的评论称，

As you said in the comment under @Braj 's answer,

轮班设置短暂的一个原因，这样序列化访问对象时，它不会序列化此对象。如果它没有标记   瞬态然后序列化分为堆栈溢出   例外 - 通过创建一个不可阻挡的循环的

workshift is set transient for a reason so that it won't serialize this object when serializing visit object. If its not marked as transient then the serialization falls into stack overflow exception - by creating an unstoppable loop

这有一个简单的解决方案。

This has a simple solution.

Workshift.java

public class Workshift {
    private final transient Context context;
    private final Visit visit;
    //for testing
    private String workshift_description;

    public Workshift(Context context,String id) {
        this.workshift_description=id;
        this.context = context;
        this.visit = new Visit(this);

    }
    public String getId() {
        return workshift_description;
    }

    public void setId(String id) {
        this.workshift_description = id;
    }
    public String toString() {
        return "[Workshift element => { WD: "+this.workshift_description+", VD : "+this.visit.getVisit_description()+"}";
    }
}

Visit.java

public class Visit {

    private final /* transient  */ Workshift workshift;

    public Visit(Workshift ws) {
        this.workshift = ws;

    }
    public String getVisit_description() {
        return "visit containing  "+ workshift.getId();
    }

}

诀窍所在位置：

The trick resides here:

GsonBuilder gsonBuilder = new GsonBuilder();
        new GraphAdapterBuilder()
        .addType(Visit.class)
        .addType(Workshift.class)
        .registerOn(gsonBuilder);

把所有在一起，

Putting all together,

public static void main(String[] args) {

        Workshift[] workshifts = new Workshift[10];
        for (int i = 0; i < workshifts.length; i++) {
            //Replace Context(i) for the real one
            workshifts[i] = new Workshift(new Context(i), "Workshift#"
                    + i);
        }
        System.out.println("Original Workshifts array:");
        for (int i = 0; i < workshifts.length; i++) {
            System.out.println(workshifts[i]);
        }
        System.out.println("===================================");

        GsonBuilder gsonBuilder = new GsonBuilder();
        new GraphAdapterBuilder()
        .addType(Visit.class)
        .addType(Workshift.class)
        .registerOn(gsonBuilder);

        Gson gson = gsonBuilder.setPrettyPrinting().create();
        String serialized = gson.toJson(workshifts);
        // System.out.println(serialized);
        Workshift[] w_array = gson.fromJson(serialized, Workshift[].class);
        // System.out.println(gson.toJson(w_array));

        System.out.println("Des-serialized Workshifts array:");
        for (int i = 0; i < w_array.length; i++) {
            System.out.println(w_array[i]);
        }
        System.out.println("===================================");

输出：

Original Workshifts array:
[Workshift element => { WD: Workshift#0, VD : visit containing  Workshift#0}
[Workshift element => { WD: Workshift#1, VD : visit containing  Workshift#1}
[Workshift element => { WD: Workshift#2, VD : visit containing  Workshift#2}
[Workshift element => { WD: Workshift#3, VD : visit containing  Workshift#3}
[Workshift element => { WD: Workshift#4, VD : visit containing  Workshift#4}
[Workshift element => { WD: Workshift#5, VD : visit containing  Workshift#5}
[Workshift element => { WD: Workshift#6, VD : visit containing  Workshift#6}
[Workshift element => { WD: Workshift#7, VD : visit containing  Workshift#7}
[Workshift element => { WD: Workshift#8, VD : visit containing  Workshift#8}
[Workshift element => { WD: Workshift#9, VD : visit containing  Workshift#9}
===================================
Des-serialized Workshifts array:
[Workshift element => { WD: Workshift#0, VD : visit containing  Workshift#0}
[Workshift element => { WD: Workshift#1, VD : visit containing  Workshift#1}
[Workshift element => { WD: Workshift#2, VD : visit containing  Workshift#2}
[Workshift element => { WD: Workshift#3, VD : visit containing  Workshift#3}
[Workshift element => { WD: Workshift#4, VD : visit containing  Workshift#4}
[Workshift element => { WD: Workshift#5, VD : visit containing  Workshift#5}
[Workshift element => { WD: Workshift#6, VD : visit containing  Workshift#6}
[Workshift element => { WD: Workshift#7, VD : visit containing  Workshift#7}
[Workshift element => { WD: Workshift#8, VD : visit containing  Workshift#8}
[Workshift element => { WD: Workshift#9, VD : visit containing  Workshift#9}
===================================

有没有计算器的错误。

There's no StackOverflow error.

如果你取消注释行

// System.out.println(serialized);

输出会是这样的：

The output would be like this:

[
  {
    "0x1": {
      "visit": "0x2",
      "workshift_description": "Workshift#0"
    },
    "0x2": {
      "workshift": "0x1"
    }
  },
  {
    "0x1": {
      "visit": "0x2",
      "workshift_description": "Workshift#1"
    },
    "0x2": {
      "workshift": "0x1"
    }
  },
  {
    "0x1": {
      "visit": "0x2",
      "workshift_description": "Workshift#2"
    },
    "0x2": {
      "workshift": "0x1"
    }
  },
  {
    "0x1": {
      "visit": "0x2",
      "workshift_description": "Workshift#3"
    },
    "0x2": {
      "workshift": "0x1"
    }
  },
  {
    "0x1": {
      "visit": "0x2",
      "workshift_description": "Workshift#4"
    },
    "0x2": {
      "workshift": "0x1"
    }
  },
  {
    "0x1": {
      "visit": "0x2",
      "workshift_description": "Workshift#5"
    },
    "0x2": {
      "workshift": "0x1"
    }
  },
  {
    "0x1": {
      "visit": "0x2",
      "workshift_description": "Workshift#6"
    },
    "0x2": {
      "workshift": "0x1"
    }
  },
  {
    "0x1": {
      "visit": "0x2",
      "workshift_description": "Workshift#7"
    },
    "0x2": {
      "workshift": "0x1"
    }
  },
  {
    "0x1": {
      "visit": "0x2",
      "workshift_description": "Workshift#8"
    },
    "0x2": {
      "workshift": "0x1"
    }
  },
  {
    "0x1": {
      "visit": "0x2",
      "workshift_description": "Workshift#9"
    },
    "0x2": {
      "workshift": "0x1"
    }
  }

]

这是因为GSON被替换您参考，以避免堆栈溢出异常。这就像模拟指针的

That's because Gson is replacing your references, in order to avoid that stack overflow exception. It's like emulating pointers

希望它帮助。

注意：记住复制文件GraphAdapterBuilder.java并更改行

Note: Remember to copy the files GraphAdapterBuilder.java and change the line

private final ConstructorConstructor constructorConstructor = new ConstructorConstructor();

与

私人最终ConstructorConstructor constructorConstructor =新ConstructorConstructor（instanceCreators）;

这不能编译，否则。也许这是固定的现在。

It won't compile otherwise. Maybe it's fixed right now.