com.hazelcast.org.apache.calcite.util.DelegatingInvocationHandler Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to you under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.hazelcast.org.apache.calcite.util;
import com.hazelcast.org.checkerframework.checker.nullness.qual.Nullable;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
/**
* A class derived from DelegatingInvocationHandler
handles a
* method call by looking for a method in itself with identical parameters. If
* no such method is found, it forwards the call to a fallback object, which
* must implement all of the interfaces which this proxy implements.
*
* It is useful in creating a wrapper class around an interface which may
* change over time.
*
* Example:
*
*
* import java.sql.Connection;
* Connection connection = ...;
* Connection tracingConnection = (Connection) Proxy.newProxyInstance(
* null,
* new Class[] {Connection.class},
* new DelegatingInvocationHandler() {
* protected Object getTarget() {
* return connection;
* }
* Statement createStatement() {
* System.out.println("statement created");
* return connection.createStatement();
* }
* });
*
*/
public abstract class DelegatingInvocationHandler implements InvocationHandler {
//~ Methods ----------------------------------------------------------------
@Override public @Nullable Object invoke(
Object proxy,
Method method,
@Nullable Object[] args) throws Throwable {
Class clazz = getClass();
Method matchingMethod;
try {
matchingMethod =
clazz.getMethod(
method.getName(),
method.getParameterTypes());
} catch (NoSuchMethodException | SecurityException e) {
matchingMethod = null;
}
try {
if (matchingMethod != null) {
// Invoke the method in the derived class.
return matchingMethod.invoke(this, args);
} else {
// Invoke the method on the proxy.
return method.invoke(
getTarget(),
args);
}
} catch (InvocationTargetException e) {
throw Util.first(e.getCause(), e);
}
}
/**
* Returns the object to forward method calls to, should the derived class
* not implement the method. Generally, this object will be a member of the
* derived class, supplied as a parameter to its constructor.
*/
protected abstract Object getTarget();
}
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