Interface InvocationHandler

public Object invoke(Object proxy,
                     Method method,
                     Object[] args)
            throws Throwable

When a method is invoked on a proxy instance, it is wrapped and this method is called instead, so that you may decide at runtime how the original method should behave.

Parameters:

proxy - the instance that the wrapped method should be invoked on. When this method is called by a Proxy object, `proxy' will be an instance of Proxy, and oddly enough, Proxy.getInvocationHandler(proxy) will return this!

method - the reflected method to invoke on the proxy. When this method is called by a Proxy object, 'method' will be the reflection object owned by the declaring class or interface, which may be a supertype of the interfaces the proxy directly implements.

args - the arguments passed to the original method, or null if the method takes no arguments. (But also be prepared to handle a 0-length array). Arguments of primitive type, such as boolean or int, are wrapped in the appropriate class such as Boolean or Integer.

Returns:

whatever is necessary to return from the wrapped method. If the wrapped method is void, the proxy instance will ignore it. If the wrapped method returns a primitive, this must be the correct wrapper type whose value is exactly assignable to the appropriate type (no widening will be performed); a null object in this case causes a NullPointerException. In all remaining cases, if the returned object is not assignment compatible to the declared type of the original method, the proxy instance will generate a ClassCastException.

Throws:

Throwable - this interface is listed as throwing anything, but the implementation should only throw unchecked exceptions and exceptions listed in the throws clause of all methods being overridden by the proxy instance. If something is thrown that is not compatible with the throws clause of all overridden methods, the proxy instance will wrap the exception in an UndeclaredThrowableException. Note that an exception listed in the throws clause of the `method' parameter might not be declared in additional interfaces also implemented by the proxy object.

See Also:

Proxy, UndeclaredThrowableException