How to determine the Type of an object at runtime in Java for gson
Take a look at the following code, which works fine:
MyData myData = new MyData(1, "one");
MyData myData2 = new MyData(2, "two");
MyData [] data = {myData, myData2};
String toJson = gson.toJson(data, MyData[].class);
MyData [] newData = gson.fromJson(toJson, MyData[].class);
MyData is just a simple class with int and String fields. This works perfectly fine. But what if the class is not known until runtime? e.g. It might not be "MyData", but could be a completely different class. The only thing we know is the name of the class (represented as a string), which was previously determi开发者_开发技巧ned by the sender using Class.forName.
It works fine if the object is not an array, like so:
final Class<?> componentType = Class.forName(componentClassName);
context.deserialize(someElement, componentType);
The above technique doesn't work for arrays though.
Any suggestions?
Do you mean that MyData would become a generic type T? If so you won't be able to do this due to Javas type erasure. The type T is only available at compile time.
You could create a method like:
public T decodeJSON(String json, Class<T> type) {
GSON gson = new GSON();
return gson.fromJson(json, type);
}
In java you can get the class of an object by calling
object.getClass();
From java docs:
class Test {
public static void main(String[] args) {
int[] ia = new int[3];
System.out.println(ia.getClass());
System.out.println(ia.getClass().getSuperclass());
}
}
which prints:
class [I
class java.lang.Object
String toJson = gson.toJson(Class.forName(obj, runtimeClassName + "[]"));
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