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Java example source code file (ClientPreemptiveBasicAuthentication.java)

This example source code file (ClientPreemptiveBasicAuthentication.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

authscheme, authscope, authstate, basichttpcontext, basicscheme, credentialsprovider, defaulthttpclient, httpexception, httpget, httphost, httprequestinterceptor, io, ioexception, no, preemptiveauth

The ClientPreemptiveBasicAuthentication.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 org.apache.http.HttpEntity;
import org.apache.http.HttpException;
import org.apache.http.HttpHost;
import org.apache.http.HttpRequest;
import org.apache.http.HttpRequestInterceptor;
import org.apache.http.HttpResponse;
import org.apache.http.auth.AuthScheme;
import org.apache.http.auth.AuthScope;
import org.apache.http.auth.AuthState;
import org.apache.http.auth.Credentials;
import org.apache.http.auth.UsernamePasswordCredentials;
import org.apache.http.client.CredentialsProvider;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.protocol.ClientContext;
import org.apache.http.impl.auth.BasicScheme;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.protocol.BasicHttpContext;
import org.apache.http.protocol.ExecutionContext;
import org.apache.http.protocol.HttpContext;

 * An example of HttpClient can be customized to authenticate 
 * preemptively using BASIC scheme.
 * <b/>
 * Generally, preemptive authentication can be considered less
 * secure than a response to an authentication challenge
 * and therefore discouraged.
 * <b/>
 * This code is NOT officially supported! Use at your risk.
public class ClientPreemptiveBasicAuthentication {

    public static void main(String[] args) throws Exception {

        DefaultHttpClient httpclient = new DefaultHttpClient();

                new AuthScope("localhost", 80), 
                new UsernamePasswordCredentials("username", "password"));

        BasicHttpContext localcontext = new BasicHttpContext();

        // Generate BASIC scheme object and stick it to the local 
        // execution context
        BasicScheme basicAuth = new BasicScheme();
        localcontext.setAttribute("preemptive-auth", basicAuth);
        // Add as the first request interceptor
        httpclient.addRequestInterceptor(new PreemptiveAuth(), 0);
        HttpHost targetHost = new HttpHost("localhost", 80, "http"); 

        HttpGet httpget = new HttpGet("/");

        System.out.println("executing request: " + httpget.getRequestLine());
        System.out.println("to target: " + targetHost);
        for (int i = 0; i < 3; i++) {
            HttpResponse response = httpclient.execute(targetHost, httpget, localcontext);
            HttpEntity entity = response.getEntity();

            if (entity != null) {
                System.out.println("Response content length: " + entity.getContentLength());
        // When HttpClient instance is no longer needed, 
        // shut down the connection manager to ensure
        // immediate deallocation of all system resources
    static class PreemptiveAuth implements HttpRequestInterceptor {

        public void process(
                final HttpRequest request, 
                final HttpContext context) throws HttpException, IOException {
            AuthState authState = (AuthState) context.getAttribute(
            // If no auth scheme avaialble yet, try to initialize it preemptively
            if (authState.getAuthScheme() == null) {
                AuthScheme authScheme = (AuthScheme) context.getAttribute(
                CredentialsProvider credsProvider = (CredentialsProvider) context.getAttribute(
                HttpHost targetHost = (HttpHost) context.getAttribute(
                if (authScheme != null) {
                    Credentials creds = credsProvider.getCredentials(
                            new AuthScope(
                    if (creds == null) {
                        throw new HttpException("No credentials for preemptive authentication");

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