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The AWS SDK for Java - Core module holds the classes that are used by the individual service clients to interact with Amazon Web Services. Users need to depend on aws-java-sdk artifact for accessing individual client classes.
/*
* Copyright 2010-2024 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License").
* You may not use this file except in compliance with the License.
* A copy of the License is located at
*
* http://aws.amazon.com/apache2.0
*
* or in the "license" file accompanying this file. This file 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.amazonaws.handlers;
import com.amazonaws.AmazonClientException;
import com.amazonaws.util.ClassLoaderHelper;
import com.amazonaws.util.StringUtils;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.List;
/**
* Factory for creating request/response handler chains.
*/
public class HandlerChainFactory {
private static final String GLOBAL_HANDLER_PATH = "com/amazonaws/global/handlers/request.handler2s";
/**
* For backward compatibility, constructs a new request handler chain adapted to {@link RequestHandler2} by analyzing the
* specified classpath resource.
*
* @param resource The resource to load from the classpath containing the list of request handlers to instantiate.
* @return A list of request handlers based on the handlers referenced in the specified resource.
*/
public List newRequestHandlerChain(String resource) {
return createRequestHandlerChain(resource, RequestHandler.class);
}
/**
* Constructs a new request handler (v2) chain by analyzing the specified classpath resource.
*
* @param resource The resource to load from the classpath containing the list of request handlers to instantiate.
* @return A list of request handlers based on the handlers referenced in the specified resource.
*/
public List newRequestHandler2Chain(String resource) {
return createRequestHandlerChain(resource, RequestHandler2.class);
}
public List getGlobalHandlers() {
List handlers = new ArrayList();
BufferedReader fileReader = null;
try {
List globalHandlerListLocations = Collections
.list(getGlobalHandlerResources());
for (URL url : globalHandlerListLocations) {
fileReader = new BufferedReader(new InputStreamReader(url.openStream(), StringUtils.UTF8));
while (true) {
String requestHandlerClassName = fileReader.readLine();
if (requestHandlerClassName == null) {
break;
}
RequestHandler2 requestHandler = createRequestHandler(requestHandlerClassName, RequestHandler2.class);
if (requestHandler == null) {
continue;
}
handlers.add(requestHandler);
}
}
} catch (Exception e) {
throw new AmazonClientException("Unable to instantiate request handler chain for client: "
+ e.getMessage(), e);
} finally {
try {
if (fileReader != null) {
fileReader.close();
}
} catch (IOException e) {
}
}
return handlers;
}
private Enumeration getGlobalHandlerResources() throws IOException {
// Classloader may be null if loaded by bootstrap classloader.
if (HandlerChainFactory.class.getClassLoader() == null) {
return ClassLoader.getSystemResources(GLOBAL_HANDLER_PATH);
}
return HandlerChainFactory.class.getClassLoader().getResources(GLOBAL_HANDLER_PATH);
}
private RequestHandler2 createRequestHandler(String handlerClassName, Class handlerApiClass)
throws ClassNotFoundException, InstantiationException, IllegalAccessException {
handlerClassName = handlerClassName.trim();
if (handlerClassName.equals("")) {
return null;
}
Class requestHandlerClass = ClassLoaderHelper.loadClass(
handlerClassName,
handlerApiClass, getClass());
Object requestHandlerObject = requestHandlerClass.newInstance();
if (handlerApiClass.isInstance(requestHandlerObject)) {
if (handlerApiClass == RequestHandler2.class) {
return (RequestHandler2) requestHandlerObject;
} else if (handlerApiClass == RequestHandler.class) {
return RequestHandler2.adapt((RequestHandler) requestHandlerObject);
} else {
throw new IllegalStateException();
}
} else {
throw new AmazonClientException(
"Unable to instantiate request handler chain for client. "
+ "Listed request handler ('"
+ handlerClassName + "') "
+ "does not implement the "
+ handlerApiClass + " API.");
}
}
private List createRequestHandlerChain(String resource, Class handlerApiClass) {
List handlers = new ArrayList();
BufferedReader reader = null;
try {
InputStream input = getClass().getResourceAsStream(resource);
if (input == null) {
return handlers;
}
reader = new BufferedReader(new InputStreamReader(input, StringUtils.UTF8));
while (true) {
String requestHandlerClassName = reader.readLine();
if (requestHandlerClassName == null) {
break;
}
RequestHandler2 requestHandler = createRequestHandler(requestHandlerClassName, handlerApiClass);
if (requestHandler == null) {
continue;
}
handlers.add(requestHandler);
}
} catch (Exception e) {
throw new AmazonClientException("Unable to instantiate request handler chain for client: "
+ e.getMessage(), e);
} finally {
try {
if (reader != null) {
reader.close();
}
} catch (IOException e) {
}
}
return handlers;
}
}