Github user StephanEwen commented on the pull request:
https://github.com/apache/incubator-flink/pull/85#issuecomment-50670878
Simple type extraction from Lambdas (limited to non-generic parameters):
```java
public static Class<?>[] getLambdaParameters(Object lambda) {
for (Class<?> clazz = lambda.getClass(); clazz != null; clazz =
clazz.getSuperclass()) {
try {
Method replaceMethod =
clazz.getDeclaredMethod("writeReplace");
replaceMethod.setAccessible(true);
Object serializedForm =
replaceMethod.invoke(lambda);
if (serializedForm instanceof SerializedLambda)
{
SerializedLambda sl =
(SerializedLambda) serializedForm;
return getTypesFromSerializedLambda(sl);
}
}
catch (NoSuchMethodException e) {
// fall through the loop and try the next class
}
catch (Throwable t) {
throw new RuntimeException(t);
}
}
throw new IllegalArgumentException("Not a serialized Lambda");
}
public static Class<?>[] getTypesFromSerializedLambda(SerializedLambda
sl) throws Exception {
String sig = sl.getImplMethodSignature();
if (!sig.startsWith("(")) {
throw new Exception("Parse Error");
}
String parameters = sig.substring(1, sig.indexOf(')'));
String[] params = parameters.split(";");
List<Class<?>> classes = new ArrayList<>();
for (String p : params) {
if (!p.startsWith("L")) {
throw new Exception("Parse Error");
}
p = p.substring(1);
p = p.replace('/', '.');
classes.add(Class.forName(p));
}
return (Class<?>[]) classes.toArray(new
Class<?>[classes.size()]);
}
```
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