我可以实例化一个超类，并根据提供的参数来实例化一个特定的子类 [英] Can I instantiate a superclass and have a particular subclass be instantiated based on the parameters supplied
问题描述
我使用Google的GSON套件 http://code.google.com/p/google -gson /
I am using Google's GSON package http://code.google.com/p/google-gson/
我将JSON转换为Java。
I am converting JSON to Java.
我有这段代码在这里我做了转换。
I have this fragment of code where I do the conversion.
Gson gson = new Gson();
Type collectionType = new TypeToken<Collection<QueryProperty>>() {}.getType();
Collection<QueryProperty> queryProperties = gson.fromJson(query, collectionType);
我的QueryProperty类有这些字段（带getters / setters）：
My QueryProperty class has these fields (with getters/setters):
int id;
String uri;
String name;
Set<QueryValue> values;
String selected;
QueryValue类具有以下字段（与getter / setter）：
The QueryValue class had these fields (with getters/setters) perviously:
int id;
String uri;
String name;
我现在希望能有不同的类型 QueryValue。
I now want to be able to have different types of QueryValue.
我想添加一个NumericQueryValue类（QueryValue的子类），所以我可以传入一组用于查询db的边界。 / p>
I want to add a NumericQueryValue class (subclass of QueryValue), so I can pass in a set of bounds with which to query the db.
double lower;
double upper;
并且想要创建一个与QueryValue相同的新ResourceQueryValue（QueryValue的子类）：
And want to make a new ResourceQueryValue (subclass of QueryValue) which looks the same as QueryValue used to:
int id;
String uri;
String name;
无论如何，我可以让这项工作成功。这是一个通用的QueryValue类，但根据JSON提供的参数返回正确的子类。
Is there anyway I can make this work. That is have a generic QueryValue class, but have the correct subclass returned depending on the parameters that the JSON supplies.
如果我不清楚，请告诉我。
If I have not been clear please do let me know.
推荐答案
除了实现自定义的反序列化处理，Gson目前还没有一种简单的多态反序列化机制。下一个版本看起来像它将提供一个内置的解决方案。
Gson does not currently have a simple mechanism for polymorphic deserialization, other than implementing custom deserialization processing. The next release looks like it will provide a built-in solution.
前一个StackOverflow.com问题和答案（一些例子）关于此主题：
Previous StackOverflow.com Questions And Answers (Some With Examples) On This Topic:
- 反序列化带有未知编译时类型的泛型，其中一个字段指示类型
- 为GSON字段解析JSON，没有特定结构 >
- 使用google gson进行json对象序列化/反序列化
- < a href =https://stackoverflow.com/questions/5800433> gson多态性
- Deserialising a generic with unknown compile time type where a field indicates the type
- Parse JSON with no specific structure for a field with GSON
- json object serialization/deserialization using google gson
- Polymorphism with gson
这篇关于我可以实例化一个超类，并根据提供的参数来实例化一个特定的子类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！
