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Java example source code file (ClientGZipContentCompression.java)

This example source code file (ClientGZipContentCompression.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java tags/keywords

accept-encoding, defaulthttpclient, gzipdecompressingentity, headerelement, httpcontext, httpentity, httpexception, httpget, httpresponse, httpresponseinterceptor, inputstream, io, ioexception, override, string, zip

The ClientGZipContentCompression.java example source code

/*
 * ====================================================================
 * 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.examples.client;

import java.io.IOException;
import java.io.InputStream;
import java.util.zip.GZIPInputStream;

import org.apache.http.Header;
import org.apache.http.HeaderElement;
import org.apache.http.HttpEntity;
import org.apache.http.HttpException;
import org.apache.http.HttpRequest;
import org.apache.http.HttpRequestInterceptor;
import org.apache.http.HttpResponse;
import org.apache.http.HttpResponseInterceptor;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.entity.HttpEntityWrapper;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.protocol.HttpContext;
import org.apache.http.util.EntityUtils;

/**
 * Demonstration of the use of protocol interceptors to transparently 
 * modify properties of HTTP messages sent / received by the HTTP client.
 * <p/>
 * In this particular case HTTP client is made capable of transparent content 
 * GZIP compression by adding two protocol interceptors: a request interceptor
 * that adds 'Accept-Encoding: gzip' header to all outgoing requests and
 * a response interceptor that automatically expands compressed response
 * entities by wrapping them with a uncompressing decorator class. The use of
 * protocol interceptors makes content compression completely transparent to 
 * the consumer of the {@link org.apache.http.client.HttpClient HttpClient}
 * interface.
 */
public class ClientGZipContentCompression {

    public final static void main(String[] args) throws Exception {
        DefaultHttpClient httpclient = new DefaultHttpClient();

        httpclient.addRequestInterceptor(new HttpRequestInterceptor() {
           
            public void process(
                    final HttpRequest request, 
                    final HttpContext context) throws HttpException, IOException {
                if (!request.containsHeader("Accept-Encoding")) {
                    request.addHeader("Accept-Encoding", "gzip");
                }
            }

        });
        
        httpclient.addResponseInterceptor(new HttpResponseInterceptor() {
           
            public void process(
                    final HttpResponse response, 
                    final HttpContext context) throws HttpException, IOException {
                HttpEntity entity = response.getEntity();
                Header ceheader = entity.getContentEncoding();
                if (ceheader != null) {
                    HeaderElement[] codecs = ceheader.getElements();
                    for (int i = 0; i < codecs.length; i++) {
                        if (codecs[i].getName().equalsIgnoreCase("gzip")) {
                            response.setEntity(
                                    new GzipDecompressingEntity(response.getEntity())); 
                            return;
                        }
                    }
                }
            }
            
        });
        
        HttpGet httpget = new HttpGet("http://www.apache.org/"); 
        
        // Execute HTTP request
        System.out.println("executing request " + httpget.getURI());
        HttpResponse response = httpclient.execute(httpget);

        System.out.println("----------------------------------------");
        System.out.println(response.getStatusLine());
        System.out.println(response.getLastHeader("Content-Encoding"));
        System.out.println(response.getLastHeader("Content-Length"));
        System.out.println("----------------------------------------");

        HttpEntity entity = response.getEntity();
        
        if (entity != null) {
            String content = EntityUtils.toString(entity);
            System.out.println(content);
            System.out.println("----------------------------------------");
            System.out.println("Uncompressed size: "+content.length());
        }

        // When HttpClient instance is no longer needed, 
        // shut down the connection manager to ensure
        // immediate deallocation of all system resources
        httpclient.getConnectionManager().shutdown();        
    }

    static class GzipDecompressingEntity extends HttpEntityWrapper {

        public GzipDecompressingEntity(final HttpEntity entity) {
            super(entity);
        }
    
        @Override
        public InputStream getContent()
            throws IOException, IllegalStateException {

            // the wrapped entity's getContent() decides about repeatability
            InputStream wrappedin = wrappedEntity.getContent();

            return new GZIPInputStream(wrappedin);
        }

        @Override
        public long getContentLength() {
            // length of ungzipped content is not known
            return -1;
        }

    } 
    
}

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