JCH
Java Community | Help. Code. Learn.•2y ago
daysling

GSON JSON parsing based on Generic return?

public static<K> K fromJSON(String jsonData) {
   return OpenRedisJSON.gson.fromJson(jsonData, K.class); // want something like this.
}
public static<K> K fromJSON(String jsonData) {
   return OpenRedisJSON.gson.fromJson(jsonData, K.class); // want something like this.
}
11 Replies
JavaBot
JavaBot•2y ago
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szatkus
szatkus•2y ago
Not possible. You need to pass a class by an argument. Java has no way to infer that.
Kyo-chan
Kyo-chan•2y ago
Reminder that generics don't exist at runtime. Declared types that do things like class StringList extends List<String> can be analyzed at runtime to detect they're a List of Strings. But nothing else stays.
0x150
0x150•2y ago
EXCEPT with some smart compiler magic, you can actually get the "generic" type of a method
Kyo-chan
Kyo-chan•2y ago
Not sure what you mean
0x150
0x150•2y ago
<T> void test(T... dontFillMe) {
  Class<T> tClass = (Class<T>) dontFillMe.getClass().getComponentType();
}
<T> void test(T... dontFillMe) {
  Class<T> tClass = (Class<T>) dontFillMe.getClass().getComponentType();
}
it's very hacky but it does work
0x150
0x150•2y ago
No description
Kyo-chan
Kyo-chan•2y ago
I see. Hadn't seen this hack before
0x150
0x150•2y ago
it is extraordinarily hacky but it's something i wish with all my heart that generics will become actually good at some point
Kyo-chan
Kyo-chan•2y ago
It is another thing that stays, as indeed the compiler magic creates an array of the expected return type. But it is not something I'd tell someone they may do
JavaBot
JavaBot•2y ago
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