Android之网络接口篇(一)

1.发送请求，并处理返回的响应：

HttpClient  httpClient = new DefaultHttpClient(); //创建HttpClient对象

HttpGet httpGet = new HttpGet("url");//使用Get方法（post--->HttpPost）

HttpResponse res = httpClient .execute(httpGet);//调用execute()方法发送请求并返回响应

HttpEntity entity = res.getEntity();//HttpClient将响应的内容封装为HttpEntity

if(entity!=null) {

       InputStream instream = entity.getContent();

      //.......后续处理

}

2处理响应 从服务器端返回的响应封装为HttpResponse接口。HttpResponse提供了很多方法来读取和设置响应的内容，包括状态吗、HTTP头、和HTTP内容体。HttpClient推荐使用RensponseHandler来处理返回的响应，这样做的最大的好处是框架负责处理HTTP链接，无论请求是否成功，HTTP链接都会释放并返回给连接管理。使用ResponseHandler处理响应的代码如下所示。

HttpClient httpClient = new DefaultHttpClient();

HttpGet httpGet = new HttpGet("url");

ResponseHandler<byte[]> handler = new ResponseHandler<byte[]>() {

      public byte[] handleResponse(HttpResponse res)  throws ClientProtocolException,IOException {

HttpEntity entity = res.getEntity();

if(entity!=null){

return EntityUtils.toByteArray(entity);

else {

teturn null;

       }

                      }

                                                                                                                                                               } ;

byte[] response = httpClient.execute(httpGet,handler);

  }

3.设置代理 应用程序有时可能需要通过代理访问网络。

DefaultHttpClient httpClient = new DefaultHttpClient();

HttpPost proxy = new HttpPost("url");

httpClient.getPrams().setParameter(ConnRoutePNames.DERAULT_PROXY,proxy);

4.请求重发。在HttpClient框架中提供了HttpRequestRetryHandler接口处理重连的问题，开发者需要实现接口中定义的retryRequest()方法即可。

DefaultHttpClient httpClient = new DefaultHttpClient();

HttpRequestRetryHandler handler = new HttpClientRetyHandler(){

public boolean retryRequest(IOException exception,int executionCount,HttpContext context){

if(executionCount>=5){

return false;

}

if(exception instanceof NoHttpResponseException){

return true;

}

if(exception instanceof SSLHandshakeException){

return false;}

HttpRequest request =(HttpRequest) context.getAttribute(ExecuptionContext.HTTP_REQUEST);

boolean idenpotent =!(request instanceif HttpEntityEnclosingRequest);

if(idempotent) {

return true;

}

return false;

}

};

httpClient.setHttpRequestRetryHandler(handler);

}