DefaultHttpClient进行BasicAuth重复请求的问题【转】

其实一般的只要设置一个?BasicScheme?加在?DefaultHttpClient?上面即可进行?BasicAuth?认证, 但是这个简单的方法会出现一些问题, 就是需要进行认证的请求, httpClient都不会在第一次请求服务器的时候携带认证信息, 而是在请求一次被服务器拒绝后再重新发一次请求重新进行认证. 从而导致了重复请求的问题.

通过抓包显示,?DefaultHttpClient?里面的是储存了?auth?信息(用户名/密码)的, 但是所有HTTP请求都几乎会做了两遍, 第一次返回?401 unauthorized?, 然后?defaultHttpClient?马上进行第二次重复请求, 添加了?auth?信息, 才返回200, 而使用?curl?进行对同样网址进行认证请求时抓包, 结果都是只进行一个请求, 直接返回200, 由此得到了?DefaultHttpClient?在进行?BasicAuth?的这个问题.

唯一的原因只有是?HttpClient?的配置问题, 在查找了大量的关于?org.apache.http.impl.client.DefaultHttpClient?相关资料后才发现正确的配置方法, 可以说是较为复杂的.

先贴代码片段, 注意这里的代码未经过删减, 是我参与的?安能饭否?项目中的实际代码:

   /**     * Setup DefaultHttpClient     *     * <p>     * Use ThreadSafeClientConnManager.     * </p>     *     */    private void prepareHttpClient() {        // Create and initialize HTTP parameters        HttpParams params = new BasicHttpParams();        ConnManagerParams.setMaxTotalConnections(params, 10);        HttpProtocolParams.setVersion(params, HttpVersion.HTTP_1_1);        // Create and initialize scheme registry        SchemeRegistry schemeRegistry = new SchemeRegistry();        schemeRegistry.register(new Scheme("http", PlainSocketFactory                .getSocketFactory(), 80));        schemeRegistry.register(new Scheme("https", SSLSocketFactory                .getSocketFactory(), 443));        // Create an HttpClient with the ThreadSafeClientConnManager.        ClientConnectionManager cm = new ThreadSafeClientConnManager(params,                schemeRegistry);        mClient = new DefaultHttpClient(cm, params);        // TODO: need to release this connection in httpRequest()        // cm.releaseConnection(conn, validDuration, timeUnit);        // Setup BasicAuth        BasicScheme basicScheme = new BasicScheme();        mAuthScope = new AuthScope(SERVER_HOST, AuthScope.ANY_PORT);        // mClient.setAuthSchemes(authRegistry);        mClient.setCredentialsProvider(new BasicCredentialsProvider());        // Generate BASIC scheme object and stick it to the local        // execution context        localcontext = new BasicHttpContext();        localcontext.setAttribute("preemptive-auth", basicScheme);        // first request interceptor        mClient.addRequestInterceptor(preemptiveAuth, 0);    }    /**     * HttpRequestInterceptor for DefaultHttpClient     */    private HttpRequestInterceptor preemptiveAuth = new HttpRequestInterceptor() {        @Override        public void process(final HttpRequest request, final HttpContext context) {            AuthState authState = (AuthState) context                    .getAttribute(ClientContext.TARGET_AUTH_STATE);            CredentialsProvider credsProvider = (CredentialsProvider) context                    .getAttribute(ClientContext.CREDS_PROVIDER);            HttpHost targetHost = (HttpHost) context                    .getAttribute(ExecutionContext.HTTP_TARGET_HOST);            if (authState.getAuthScheme() == null) {                AuthScope authScope = new AuthScope(targetHost.getHostName(),                        targetHost.getPort());                Credentials creds = credsProvider.getCredentials(authScope);                if (creds != null) {                    authState.setAuthScheme(new BasicScheme());                    authState.setCredentials(creds);                }            }        }    };    /**     * Setup Credentials for HTTP Basic Auth     *     * @param username     * @param password     */    public void setCredentials(String username, String password) {        mUserId = username;        mPassword = password;        mClient.getCredentialsProvider().setCredentials(mAuthScope,                new UsernamePasswordCredentials(username, password));        isAuthenticationEnabled = true;    }

这里并没有太多可以解释的, 目前看来是进行?BasicAuth?的基本配置, 直接搬去用就可以了. 如果说流量和请求对你的项目来说是一种负担的话.

其实关键的地方在于:

// first request interceptormClient.addRequestInterceptor(preemptiveAuth, 0);

这里会在?httpClient?发出第一次请求前把anth信息强行添加到请求中去, 从而避免了重复请求.