Java - getting the signature of a method in an interface and the same for its Proxy implementation
I am looking for a way to extract a signature entity in Java. The reason is because I want to use the signature as a unique key in the Map for my java.lang.reflect.Proxies.
With this code:
public interface MyInterface {
public int compute(String s);
}
...
public static void main (String... args) throws Exception {
InvocationHandler handler = ...;
MyInterface i = (MyInterface) Proxy.newProxyInstance(
Beans.class.getClassLoader(),
new Class<?>[] { MyInterface.class },
handler);
Method m1 = MyInterface.class.getMethod("compute", String.class);
Method m2 = i.getClass().getMethod("compute", String.class);
System.out.printf("%b%f", m1.equals(m2));
}
The result is obviously wrong.
This code is not the code I will be using because I need it inside the InvocationHandler, but I am wondering if, regarding the implementation of the proxy and interface, is getting method.getName()
and method.getParameterTypes()
enough or should I use method.getTypeParameters()
and method.getParameterAnnotations()
?
In short: how to get a method signature that is the same for the interface and its java.lang.reflect.Proxy implementations?
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I think you want to Method
go to InvocationHandler
.
package playtest;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.HashMap;
import java.util.Map;
import org.junit.Test;
import static junit.framework.Assert.*;
interface MyInterface {
void run();
void about();
void run(String j);
}
public class TestProxyClass {
@Test
public void testDeclaringClass() throws Exception {
final Map<Method, Runnable> actions = new HashMap<Method, Runnable>();
actions.put(MyInterface.class.getMethod("run"), new Runnable() {
@Override
public void run() {
System.out.println("run");
}
} );
actions.put(MyInterface.class.getMethod("run", String.class), new Runnable() {
@Override
public void run() {
System.out.println("run string");
}
} );
actions.put(MyInterface.class.getMethod("about"), new Runnable() {
@Override
public void run() {
System.out.println("about");
}
} );
MyInterface face = (MyInterface) Proxy.newProxyInstance(getClass().getClassLoader(),
new Class<?>[] { MyInterface.class }, new InvocationHandler() {
@Override
public Object invoke(Object proxy, Method method,
Object[] args) throws Throwable {
actions.get(method).run();
return null;
}
} );
face.run();
face.about();
face.run("Hello");
}
}
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How to use the result Method.toGenericString
as a key? As far as I know, the returned string includes all the details of the signature.
Another useful thing Method m2 = i.getClass().getMethod("compute", String.class).getDeclaringClass().getMethod("compute", String.class);
. This can cause it to m1.equals(m2)
return true.
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I just had an error with the code doing this, I took the name, genericReturnType and genericParameterTypes, and I had problems working with the proxy because I lost general information.
I switched to using name, returnType and parameterTypes and it works great ...
I also considered using declaringClass, but I removed it and don't remember exactly how I did it ...
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