使用重复键来解析JSON时，Gson引发异常 [英] Make Gson throw exception on parsing JSON with duplicated key

问题描述

我正在用Gson解析简单的JSON对象。我希望它在键名重复时抛出一些错误。例如

  {
a：2，
a：3 
} 
  code> 

在我的例子中，Gson解析这样的JSON并将a设置为3.我希望它抛出一些异常。



我知道我可以将JSON解析为map，然后Gson在这种情况下抛出异常，但前提是重复键不嵌套在地图中。如果我有例如JSON是这样的：

  {
a：2，
b：{
 dup：1， 
 dup：2 
} 
} 
  

解析没有任何异常，我只有一个值为2的dup。

我能以某种方式设置Gson在这种情况下抛出错误吗？或者在 JsonObject 实例中有重复条目，这样我就可以自己检测到它（但我怀疑它是无效的 JsonObject

可重复使用的例子

pre $ c $ String $ json = {\a \：2，\a \：3};
Gson gson = new Gson（）;
JsonObject jsonObject = gson.fromJson（json，JsonObject.class）;
System.out.println（jsonObject）;


列印出来

  {a：3} 
  

解决方案

1）您可以稍微编辑一下gson的来源。这只是一个理解事物如何工作的建议。我不建议你在真实/生产环境中使用它。

Gson使用 com.google.gson.internal.LinkedTreeMap ，同时将json字符串解析为 JsonObject 。对于测试问题，您可以使用相同的名称和软件包名称将该类复制到您的项目中。

  @Override 
 public V put（K key，V value ）{
 if（key == null）{
 throw new NullPointerException（key == null）; 
} 
 
 //我在这里编辑
 if（find（key，false）！= null）{
 throw new IllegalArgumentException（'+ key.toString （）+'是json的重复键！）; 
} 
 
节点< K，V> created = find（key，true）; 
 V result = created.value; 
 created.value = value; 
返回结果; 
 
 $ / code> 

2）另一个干净的解决方案是定义要映射到的自定义类你的json字符串。然后编写自定义 TypeAdapters

3）使用解串器？我不认为这是可能的。如果你尝试使用它，你会看到你已经拥有了一个jsonObject，你的重复键被处理为一个。

I'm parsing simple JSON object with Gson. I want it to throw some error when key name is duplicated. E.g.

{
  a: 2,
  a: 3
}

In my case, Gson parses such JSON and sets a to 3. I want it to throw some exception.

I know I can parse JSON as map, and then Gson throws exception in such case, but only if the duplicated key is not nested in the map. If I have e.g. JSON like this:

{
  a: 2,
  b: {
    dup: 1,
    dup: 2
  }
}

Still, it is parsed without any exception and I have only one "dup" with value 2.

Can I somehow setup Gson to throw error in such case? Or to have duplicated entries in JsonObject instance, so that I can detect it myself (but I doubt that, as it would be invalid JsonObject)

Reproducible example

String json = "{\"a\":2, \"a\":3}";
Gson gson = new Gson();
JsonObject jsonObject = gson.fromJson(json, JsonObject.class);
System.out.println(jsonObject);

prints out

{"a":3}

解决方案

1) You may edit the source of gson a little bit. This is just a suggestion to understand how things work. I don't advice you to use this on a real/production environment.

Gson uses com.google.gson.internal.LinkedTreeMap while parsing a json string to a JsonObject. For testing issues you can copy that class into your project with the same name and package name. And edit its put method to not allow duplicate keys.

    @Override
    public V put(K key, V value) {
    if (key == null) {
      throw new NullPointerException("key == null");
    }

    // my edit here
    if(find(key, false) != null) {
        throw new IllegalArgumentException("'" + key.toString() + "' is duplicate key for json!");
    }

    Node<K, V> created = find(key, true);
    V result = created.value;
    created.value = value;
    return result;
  }

2) Another clean solution is to define custom classes which are going to map to your json strings. Then write their custom TypeAdapters

3) Do it by using a Deserializer? I don't think it is possible. If you try to use it you'll see that you already have a jsonObject there which your duplicate keys are handled as one.

这篇关于使用重复键来解析JSON时，Gson引发异常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IT屋！