Gson deserialize complex object with recursive dependencies

Question

I have several classes that contain a recursive dependency on each other and I serialize them to JSON format with Gson GraphAdapterBuilder, and it works perfectly. Now I want to deserialize them into the same structure but can't find out how.

I've made an example:

class ClassA{
    public int field;
    public ClassB parent;
    public ClassA(int f, ClassB p){
        field = f;
        parent = p;
    }
}

class ClassB{
    public Vector<ClassA> vector = new Vector<ClassA>();
}

...

ClassB b = new ClassB();        

ClassA a1 = new ClassA(1,b);
ClassA a2 = new ClassA(2,b);
ClassA a3 = new ClassA(3,b);

b.vector.add(a1);
b.vector.add(a2);
b.vector.add(a3);

//Serializing object b

GsonBuilder gsonBuilder = new GsonBuilder();

new GraphAdapterBuilder()
    .addType(ClassA.class)
    .addType(ClassB.class)
    .registerOn(gsonBuilder);

Gson gson = gsonBuilder.create();

String json = gson.toJson(b);

Output is giving me what I want:

{"0x1":{"vector":["0x2","0x3","0x4"]},"0x2":{"field":1,"parent":"0x1"},"0x3":{"field":2,"parent":"0x1"},"0x4":{"field":3,"parent":"0x1"}}

Is there a way to deserialize that json string back into object of ClassB?

lub0v · Accepted Answer · 2013-10-06T10:14:35.983

Okay, I found solution. It was very simple. Just had to use the function fromJson instead of toJson with the same GraphAdapterBuilder structure.

    ...
    GsonBuilder gsonBuilder = new GsonBuilder();
    new GraphAdapterBuilder()
            .addType(ClassA.class)
            .addType(ClassB.class)
            .registerOn(gsonBuilder);
    gson = gsonBuilder.create();
    СlassB B = gson.fromJson(json,ClassB.class);

    System.out.println("B " + B.vector);
    for(ClassA classA:B.vector){
        System.out.println(classA.field + "  " + classA.parent);
    }

Output is:

    B [ClassA@10178f2b, ClassA@7ab8584d, ClassA@5cad662c]
    1  ClassB@7c0f023c
    2  ClassB@7c0f023c
    3  ClassB@7c0f023c

score -4 · Answer 2 · answered Oct 06 '13 at 02:58

class ClassA{
    public int field;
    public String parent;
    public ClassA(int f, String parent){
        this.field = f;
        this.parent = parent;
    }
}

class ClassB{
    public List<String> vector;
}

String str1 = "{\"0x1\":{\"vector\":[\"0x2\",\"0x3\",\"0x4\"]},\"0x2\":{\"field\":1,\"parent\":\"0x1\"},\"0x3\":{\"field\":2,\"parent\":\"0x1\"},\"0x4\":{\"field\":3,\"parent\":\"0x1\"}}";

JsonParser parser = new JsonParser();
JsonObject element = (JsonObject)parser.parse(str1);
JsonElement responseWrapper = element.get("0x1");
Gson gson = new Gson();
ClassB  classB =gson.fromJson(responseWrapper,ClassB.class);
System.out.println(classB.vector);
for (String key:classB.vector) {
      responseWrapper = element.get( key);
      ClassA  classA =gson.fromJson(responseWrapper,ClassA.class);
      System.out.println(classA.field);
      System.out.println(classA.parent);

}

This is not what I needed at all. Why did you replaced the original classes into classes with fields of type String? The problem was just to use the classes with recursive dependencies. The solution that you have written is not right for me. — lub0v, Oct 06 '13 at 10:05

Gson deserialize complex object with recursive dependencies

2 Answers2

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