[英]Can I instantiate a superclass and have a particular subclass be instantiated based on the parameters supplied
I am using Google's GSON package http://code.google.com/p/google-gson/ 我正在使用Google的GSON软件包http://code.google.com/p/google-gson/
I am converting JSON to Java. 我正在将JSON转换为Java。
I have this fragment of code where I do the conversion. 我有这段代码片段在其中进行转换。
Gson gson = new Gson();
Type collectionType = new TypeToken<Collection<QueryProperty>>() {}.getType();
Collection<QueryProperty> queryProperties = gson.fromJson(query, collectionType);
My QueryProperty class has these fields (with getters/setters): 我的QueryProperty类具有以下字段(带有getter / setter):
int id;
String uri;
String name;
Set<QueryValue> values;
String selected;
The QueryValue class had these fields (with getters/setters) perviously: QueryValue类以前具有以下字段(带有getter / setter):
int id;
String uri;
String name;
I now want to be able to have different types
of QueryValue. 我现在希望能够具有不同types
的QueryValue。
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. 我想添加一个NumericQueryValue类(QueryValue的子类),因此我可以传递一组查询数据库的范围。
double lower;
double upper;
And want to make a new ResourceQueryValue (subclass of QueryValue) which looks the same as QueryValue used to: 并想要创建一个新的ResourceQueryValue(QueryValue的子类),该外观与用于以下目的的QueryValue相同:
int id;
String uri;
String name;
Is there anyway I can make this work. 无论如何,我可以做这项工作。 That is have a generic QueryValue class, but have the correct subclass returned depending on the parameters that the JSON supplies. 那是一个通用的QueryValue类,但是根据JSON提供的参数返回了正确的子类。
If I have not been clear please do let me know. 如果我不清楚,请告诉我。
Gson does not currently have a simple mechanism for polymorphic deserialization, other than implementing custom deserialization processing. 除了实现自定义反序列化处理之外,Gson当前还没有用于多态反序列化的简单机制。 The next release looks like it will provide a built-in solution. 下一个版本看起来像它将提供一个内置的解决方案。
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