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Java example source code file (HttpClient.java)

This example source code file (HttpClient.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

clientconnectionmanager, clientprotocolexception, httpclient, httpcontext, httphost, httpparams, httprequest, httpresponse, httpurirequest, io, ioexception, responsehandler, t

The HttpClient.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.client;

import java.io.IOException;

import org.apache.http.HttpHost;
import org.apache.http.HttpRequest;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpUriRequest;
import org.apache.http.conn.ClientConnectionManager;
import org.apache.http.params.HttpParams;
import org.apache.http.protocol.HttpContext;

/**
 * This interface represents only the most basic contract for HTTP request 
 * execution. It imposes no restrictions or particular details on the request 
 * execution process and leaves the specifics of state management, 
 * authentication and redirect handling up to individual implementations. 
 * This should make it easier to decorate the interface with additional 
 * functionality such as response content caching.  
 * <p/>
 * The usual execution flow can be demonstrated by the code snippet below:
 * <PRE>
 * HttpClient httpclient = new DefaultHttpClient();
 * 
 * // Prepare a request object
 * HttpGet httpget = new HttpGet("http://www.apache.org/"); 
 * 
 * // Execute the request
 * HttpResponse response = httpclient.execute(httpget);
 * 
 * // Examine the response status
 * System.out.println(response.getStatusLine());
 * 
 * // Get hold of the response entity
 * HttpEntity entity = response.getEntity();
 * 
 * // If the response does not enclose an entity, there is no need
 * // to worry about connection release
 * if (entity != null) {
 *     InputStream instream = entity.getContent();
 *     try {
 *         
 *         BufferedReader reader = new BufferedReader(
 *                 new InputStreamReader(instream));
 *         // do something useful with the response
 *         System.out.println(reader.readLine());
 *         
 *     } catch (IOException ex) {
 * 
 *         // In case of an IOException the connection will be released
 *         // back to the connection manager automatically
 *         throw ex;
 *         
 *     } catch (RuntimeException ex) {
 * 
 *         // In case of an unexpected exception you may want to abort
 *         // the HTTP request in order to shut down the underlying 
 *         // connection and release it back to the connection manager.
 *         httpget.abort();
 *         throw ex;
 *         
 *     } finally {
 * 
 *         // Closing the input stream will trigger connection release
 *         instream.close();
 *         
 *     }
 *     
 *     // When HttpClient instance is no longer needed, 
 *     // shut down the connection manager to ensure
 *     // immediate deallocation of all system resources
 *     httpclient.getConnectionManager().shutdown();        
 * }
 * </PRE>
 *
 * @since 4.0
 */
public interface HttpClient {


    /**
     * Obtains the parameters for this client.
     * These parameters will become defaults for all requests being
     * executed with this client, and for the parameters of
     * dependent objects in this client.
     *
     * @return  the default parameters
     */
    HttpParams getParams();

    /**
     * Obtains the connection manager used by this client.
     *
     * @return  the connection manager
     */
    ClientConnectionManager getConnectionManager();

    /**
     * Executes a request using the default context.
     *
     * @param request   the request to execute
     *
     * @return  the response to the request. This is always a final response,
     *          never an intermediate response with an 1xx status code.
     *          Whether redirects or authentication challenges will be returned
     *          or handled automatically depends on the implementation and
     *          configuration of this client.
     * @throws IOException in case of a problem or the connection was aborted
     * @throws ClientProtocolException in case of an http protocol error
     */
    HttpResponse execute(HttpUriRequest request)
        throws IOException, ClientProtocolException;

    /**
     * Executes a request using the given context.
     * The route to the target will be determined by the HTTP client.
     *
     * @param request   the request to execute
     * @param context   the context to use for the execution, or
     *                  <code>null to use the default context
     *
     * @return  the response to the request. This is always a final response,
     *          never an intermediate response with an 1xx status code.
     *          Whether redirects or authentication challenges will be returned
     *          or handled automatically depends on the implementation and
     *          configuration of this client.
     * @throws IOException in case of a problem or the connection was aborted
     * @throws ClientProtocolException in case of an http protocol error
     */
    HttpResponse execute(HttpUriRequest request, HttpContext context)
        throws IOException, ClientProtocolException;

    /**
     * Executes a request to the target using the default context.
     *
     * @param target    the target host for the request.
     *                  Implementations may accept <code>null
     *                  if they can still determine a route, for example
     *                  to a default target or by inspecting the request.
     * @param request   the request to execute
     *
     * @return  the response to the request. This is always a final response,
     *          never an intermediate response with an 1xx status code.
     *          Whether redirects or authentication challenges will be returned
     *          or handled automatically depends on the implementation and
     *          configuration of this client.
     * @throws IOException in case of a problem or the connection was aborted
     * @throws ClientProtocolException in case of an http protocol error
     */
    HttpResponse execute(HttpHost target, HttpRequest request)
        throws IOException, ClientProtocolException;

    /**
     * Executes a request to the target using the given context.
     *
     * @param target    the target host for the request.
     *                  Implementations may accept <code>null
     *                  if they can still determine a route, for example
     *                  to a default target or by inspecting the request.
     * @param request   the request to execute
     * @param context   the context to use for the execution, or
     *                  <code>null to use the default context
     *
     * @return  the response to the request. This is always a final response,
     *          never an intermediate response with an 1xx status code.
     *          Whether redirects or authentication challenges will be returned
     *          or handled automatically depends on the implementation and
     *          configuration of this client.
     * @throws IOException in case of a problem or the connection was aborted
     * @throws ClientProtocolException in case of an http protocol error
     */
    HttpResponse execute(HttpHost target, HttpRequest request,
                         HttpContext context)
        throws IOException, ClientProtocolException;

    /**
     * Executes a request using the default context and processes the
     * response using the given response handler.
     *
     * @param request   the request to execute
     * @param responseHandler the response handler
     *
     * @return  the response object as generated by the response handler.
     * @throws IOException in case of a problem or the connection was aborted
     * @throws ClientProtocolException in case of an http protocol error
     */
    <T> T execute(
            HttpUriRequest request, 
            ResponseHandler<? extends T> responseHandler)
        throws IOException, ClientProtocolException;

    /**
     * Executes a request using the given context and processes the
     * response using the given response handler.
     *
     * @param request   the request to execute
     * @param responseHandler the response handler
     *
     * @return  the response object as generated by the response handler.
     * @throws IOException in case of a problem or the connection was aborted
     * @throws ClientProtocolException in case of an http protocol error
     */
    <T> T execute(
            HttpUriRequest request, 
            ResponseHandler<? extends T> responseHandler,
            HttpContext context)
        throws IOException, ClientProtocolException;

    /**
     * Executes a request to the target using the default context and 
     * processes the response using the given response handler.
     *
     * @param target    the target host for the request.
     *                  Implementations may accept <code>null
     *                  if they can still determine a route, for example
     *                  to a default target or by inspecting the request.
     * @param request   the request to execute
     * @param responseHandler the response handler
     *
     * @return  the response object as generated by the response handler.
     * @throws IOException in case of a problem or the connection was aborted
     * @throws ClientProtocolException in case of an http protocol error
     */
    <T> T execute(
            HttpHost target, 
            HttpRequest request,
            ResponseHandler<? extends T> responseHandler)
        throws IOException, ClientProtocolException;
    
    /**
     * Executes a request to the target using the given context and 
     * processes the response using the given response handler.
     *
     * @param target    the target host for the request.
     *                  Implementations may accept <code>null
     *                  if they can still determine a route, for example
     *                  to a default target or by inspecting the request.
     * @param request   the request to execute
     * @param responseHandler the response handler
     * @param context   the context to use for the execution, or
     *                  <code>null to use the default context
     *
     * @return  the response object as generated by the response handler.
     * @throws IOException in case of a problem or the connection was aborted
     * @throws ClientProtocolException in case of an http protocol error
     */
    <T> T execute(
            HttpHost target, 
            HttpRequest request,
            ResponseHandler<? extends T> responseHandler, 
            HttpContext context)
        throws IOException, ClientProtocolException;
    
}

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