I'm trying to understand Java 11 more, so I'm writing some test code. Right now I'm trying to understand if there is a right way to cast Method to any of the java.util.function interfaces, for example to Consumer.
The way I found is to create a lambda adapter around the Method#invoke
method:
public void registerCallbacks(final Object annotated) {
Class clazz = annotated.getClass();
for (Method method : clazz.getDeclaredMethods()) {
if (method.isAnnotationPresent(Callback.class)) {
Callback registration = method.getAnnotation(Callback.class);
List<String> warnings = new ArrayList<>(3);
if (!Modifier.isPublic(method.getModifiers()))
warnings.add(String.format("Method %s must be public", method));
if (method.getParameterCount() != 1)
warnings.add(String.format("Method %s must consume only one argument", method));
if (method.getParameterCount() == 1 && !method.getParameterTypes()[0].equals(Integer.class))
warnings.add(String.format("Method %s must consume %s", method, Integer.class));
if (!warnings.isEmpty()) {
warnings.forEach(log::warn);
continue;
}
CALLBACKS_MAPPER.registerCallback((param) -> {
try {
method.invoke(annotated, param);
} catch (IllegalAccessException | InvocationTargetException e) {
// Should not happen due to checks before.
log.warn(String.format("Could not invoke %s on %s with %s", method, annotated, param), e);
}
});
log.info("Registered {} as a callback", method);
}
}
}
However I want to avoid writing
CALLBACKS_MAPPER.registerCallback((param) -> {
try {
method.invoke(annotated, param);
} catch (IllegalAccessException | InvocationTargetException e) {
// Should not happen due to checks before.
log.warn(String.format("Could not invoke %s on %s with %s", method, annotated, param), e);
}
});
in favor of something simpler, like
CALLBACKS_MAPPER.registerCallback(SomeApacheLib.methodToFunction(annotated, method));
➥ So, is there a way to map old Java 1.1 reflection library to newer Java 8 functional interfaces, or it is me being stupid and the abovementioned solution with lambda is fine as it is?
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