Java tutorial
/* * ==================================================================== * 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. * ==================================================================== * * This software consists of voluntary contributions made by many * individuals on behalf of the Apache Software Foundation. For more * information on the Apache Software Foundation, please see * <http://www.apache.org/>. * */ package org.apache.http.nio.protocol; import java.io.IOException; import org.apache.http.HttpEntity; import org.apache.http.HttpException; import org.apache.http.HttpResponse; import org.apache.http.annotation.ThreadSafe; import org.apache.http.entity.ContentType; import org.apache.http.nio.ContentDecoder; import org.apache.http.nio.IOControl; import org.apache.http.protocol.HttpContext; /** * Abstract {@link HttpAsyncResponseConsumer} implementation that relieves its * subclasses form having to synchronize access to internal instance variables * and provides a number of protected methods that they need to implement. * * @since 4.2 */ @ThreadSafe public abstract class AbstractAsyncResponseConsumer<T> implements HttpAsyncResponseConsumer<T> { private volatile boolean completed; private volatile T result; private volatile Exception ex; public AbstractAsyncResponseConsumer() { super(); } /** * Invoked when a HTTP response message is received. Please note * that the {@link #onContentReceived(ContentDecoder, IOControl)} method * will be invoked only if the response messages has a content entity * enclosed. * * @param response HTTP response message. * @throws HttpException in case of HTTP protocol violation * @throws IOException in case of an I/O error */ protected abstract void onResponseReceived(HttpResponse response) throws HttpException, IOException; /** * Invoked to process a chunk of content from the {@link ContentDecoder}. * The {@link IOControl} interface can be used to suspend input events * if the consumer is temporarily unable to consume more content. * <p/> * The consumer can use the {@link ContentDecoder#isCompleted()} method * to find out whether or not the message content has been fully consumed. * * @param decoder content decoder. * @param ioctrl I/O control of the underlying connection. * @throws IOException in case of an I/O error */ protected abstract void onContentReceived(ContentDecoder decoder, IOControl ioctrl) throws IOException; /** * Invoked if the response message encloses a content entity. * * @param entity HTTP entity * @param contentType expected content type. * @throws IOException in case of an I/O error */ protected abstract void onEntityEnclosed(HttpEntity entity, ContentType contentType) throws IOException; /** * Invoked to generate a result object from the received HTTP response * message. * * @param context HTTP context. * @return result of the response processing. * @throws Exception in case of an abnormal termination. */ protected abstract T buildResult(HttpContext context) throws Exception; /** * Invoked to release all system resources currently allocated. */ protected abstract void releaseResources(); /** * Invoked when the consumer is being closed. * @throws IOException may be thrown by subclassses * * @since 4.3 */ protected void onClose() throws IOException { } /** * Use {@link #onResponseReceived(HttpResponse)} instead. */ public final synchronized void responseReceived(final HttpResponse response) throws IOException, HttpException { onResponseReceived(response); final HttpEntity entity = response.getEntity(); if (entity != null) { final ContentType contentType = ContentType.getOrDefault(entity); onEntityEnclosed(entity, contentType); } } /** * Use {@link #onContentReceived(ContentDecoder, IOControl)} instead. */ public final synchronized void consumeContent(final ContentDecoder decoder, final IOControl ioctrl) throws IOException { onContentReceived(decoder, ioctrl); } /** * Use {@link #buildResult(HttpContext)} instead. */ public final synchronized void responseCompleted(final HttpContext context) { if (this.completed) { return; } this.completed = true; try { this.result = buildResult(context); } catch (final Exception ex) { this.ex = ex; } finally { releaseResources(); } } public final synchronized boolean cancel() { if (this.completed) { return false; } this.completed = true; releaseResources(); return true; } public final synchronized void failed(final Exception ex) { if (this.completed) { return; } this.completed = true; this.ex = ex; releaseResources(); } public final synchronized void close() throws IOException { if (this.completed) { return; } this.completed = true; releaseResources(); onClose(); } public Exception getException() { return this.ex; } public T getResult() { return this.result; } public boolean isDone() { return this.completed; } }