Gson fromJson反序列化泛型

Question

gson.fromJson(responseBody, new TypeToken<T>() {}.getType());

gson.fromJson(responseBody, new TypeToken<ArrayList<T>>() {}.getType())

您将获得LinkedTreeMap对象（或LinkedTreeMap对象列表），而不是作为T传递的实际对象（或第二种情况下的实际对象列表）。

如果您想要一个仍然想要反序列化泛型类型对象(-s)，请参阅下面的答案。

+红利：LoopJ+GSON的最终通用解决方案

如何获取泛型接口的具体类型

Java类型Generic作为GSON的参数

Answer 1

将JSON对象反序列化为泛型类型java对象

首先，我们需要获得泛型类型T的实际类。

我们可以通过传递类本身(class cl )或者通过从具有泛型类型的对象获取类(someObject someObjectWithGenericType )来实现。我将在例子中使用第二种情况。

public <T> T getObject(String json, SomeObject<T> someObjectWithGenericType) {
    Class cl = getTypeClassOfObject(someObjWithGenericType);
    T object = gson.fromJson(json, new Element<T>(cl));
    return object;
}

private Class getTypeClassOfObject(Object obj) {
    return (Class) ((ParameterizedType) obj.getClass().getGenericSuperclass()).getActualTypeArguments()[0];
}

private class Element<T> implements ParameterizedType {

    private Class<T> cl;

    public Element(Class<T> cl) {
        this.cl = cl;
    }

    public Type[] getActualTypeArguments() {
        return new Type[] {cl};
    }

    public Type getRawType() {
        return cl;
    }

    public Type getOwnerType() {
        return null;
    }
}

private Class getTypeClassOfInterfaceObject(Object obj) {
    return (Class) ((ParameterizedType) obj.getClass().getGenericInterfaces()[0]).getActualTypeArguments()[0];
}

将JSON数组反序列化为泛型类型java对象列表

相同的想法，但我们有一个不同的特殊类来帮助Gson进行反序列化：

public <T> List<T> getList(String json, SomeObject<T> someObjectWithGenericType) {
    Class cl = getTypeClassOfObject(someObjWithGenericType);
    List<T> list = gson.fromJson(json, new ListWithElements<T>(cl));
    return list;
}

private class ListWithElements<T> implements ParameterizedType {

    private Class<T> elementsClass;

    public ListWithElements(Class<T> elementsClass) {
        this.elementsClass = elementsClass;
    }

    public Type[] getActualTypeArguments() {
        return new Type[] {elementsClass};
    }

    public Type getRawType() {
        return List.class;
    }

    public Type getOwnerType() {
        return null;
    }
}

奖金

public <T> void getObject(String url, HashMap<String, String> paramsMap, final GetObjectCallback<T> callback) {
    RequestParams params = convertParams(paramsMap);
    client.get(url, params, new TextHttpResponseHandler() {
        @Override
        public void onSuccess(int statusCode, Header[] headers, String responseBody) {
            try {
                Class cl = getTypeClassOfInterfaceObject(callback);
                T object = gson.fromJson(responseBody, new Element<T>(cl));
                if (object != null) {
                    callback.onSuccess(object);
                } else {
                    callback.onFailure();
                }
            } catch (Exception e) {
                e.printStackTrace();
                callback.onFailure();
            }
        }

        @Override
        public void onFailure(int statusCode, Header[] headers, String responseBody, Throwable error) {
            error.printStackTrace();
            callback.onFailure();
        }
    });
}

private RequestParams convertParams(HashMap<String, String> paramsMap) {
    RequestParams params = new RequestParams();
    if (paramsMap != null) {
        for (String key : paramsMap.keySet()) {
            params.put(key, paramsMap.get(key));
        }
    }
    return params;
}

public interface GetObjectCallback<T> {
    void onSuccess(T item);
    void onFailure();
}

loopj+Gson，带有泛型：列表

public <T> void getList(String url, HashMap<String, String> paramsMap, final GetListCallback<T> callback) {
    RequestParams params = convertParams(paramsMap);
    client.get(url, params, new TextHttpResponseHandler() {
        @Override
        public void onSuccess(int statusCode, Header[] headers, String responseBody) {
            try {
                Class cl = getTypeClassOfInterfaceObject(callback);
                List<T> list  = gson.fromJson(responseBody, new ListWithElements<T>(cl));
                if (list != null) {
                    callback.onSuccess(list);
                } else {
                    callback.onFailure();
                }
            } catch (Exception e) {
                e.printStackTrace();
                callback.onFailure();
            }
        }

        @Override
        public void onFailure(int statusCode, Header[] headers, String responseBody, Throwable error) {
            error.printStackTrace();
            callback.onFailure();
        }
    });
}

public interface GetListCallback<T> {
    void onSuccess(List<T> list);
    void onFailure();
}

用法：object

api.getObject(URL, paramsMap, new GetObjectCallback<NewsItem>() {
    @Override
    public void onSuccess(NewsItem item) {
        // do something
    }

    @Override
    public void onFailure() {
        // do something
    }
});

用法：列表

api.getList(URL, paramsMap, new GetListCallback<Comment>() {
    @Override
    public void onSuccess(List<Comment> list) {
        // do something
    }

    @Override
    public void onFailure() {
        // do something
    }
});