HttpClient与HttpURLConnection分析

1.HttpClient
　　Android SDK中包含了HttpClient，在Android6.0版本直接删除了HttpClient类库，如果想使用解决方法
是在android studio相应的module下的build.gradle中加入

android {
    useLibrary 'org.apache.http.legacy'
     }

HttpClient的GET请求

先用DefaultHttpClient类来实例化一个HttpClient，并配置好默认的请求参数：

 //创建HttpClient
   private HttpClient createHttpClient() {
       HttpParams mDefaultHttpParams = new BasicHttpParams();
       //设置连接超时
       HttpConnectionParams.setConnectionTimeout(mDefaultHttpParams, 10000);
       //设置请求超时
       HttpConnectionParams.setSoTimeout(mDefaultHttpParams, 10000);
       HttpConnectionParams.setTcpNoDelay(mDefaultHttpParams, true);
       HttpProtocolParams.setVersion(mDefaultHttpParams, HttpVersion.HTTP_1_1);
       HttpProtocolParams.setContentCharset(mDefaultHttpParams, HTTP.UTF_8);
       //持续握手
       HttpProtocolParams.setUseExpectContinue(mDefaultHttpParams, true);
       HttpClient mHttpClient = new DefaultHttpClient(mDefaultHttpParams);
       return mHttpClient;
   }

然后创建HttpGet和HttpClient，请求网络并得到HttpResponse，并对HttpResponse进行处理：

 private void useHttpClientGet(String url) {
      HttpGet mHttpGet = new HttpGet(url);
      mHttpGet.addHeader("Connection", "Keep-Alive");
      try {
          HttpClient mHttpClient = createHttpClient();
          HttpResponse mHttpResponse = mHttpClient.execute(mHttpGet);
          HttpEntity mHttpEntity = mHttpResponse.getEntity();
          int code = mHttpResponse.getStatusLine().getStatusCode();
          if (null != mHttpEntity) {
              InputStream mInputStream = mHttpEntity.getContent();
              String respose = converStreamToString(mInputStream);
              Log.i("wangshu", "请求状态码:" + code + "\n请求结果:\n" + respose);
              mInputStream.close();
          }
      } catch (IOException e) {
          e.printStackTrace();
      }
  }

converStreamToString方法将请求结果转换成String类型：

 private String converStreamToString(InputStream is) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(is));
        StringBuffer sb = new StringBuffer();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "\n");
        }
        String respose = sb.toString();
        return respose;
    }

最后我们开启线程访问百度：

 new Thread(new Runnable() {
          @Override
          public void run() {
              useHttpClientGet("http://www.baidu.com");
          }
      }).start();

请求的返回结果，请求状态码为200，结果就是个html页。
GET请求的参数暴露在URL中，这有些不大妥当，而且URL的长度也有限制：长度在2048字符之内，在HTTP 1.1后URL长度才没有限制。一般情况下POST可以替代GET，接下来我们来看看HttpClient的POST请求。

HttpClient的POST请求

post请求和get类似就是需要配置要传递的参数：

 private void useHttpClientPost(String url) {
    HttpPost mHttpPost = new HttpPost(url);
    mHttpPost.addHeader("Connection", "Keep-Alive");
    try {
        HttpClient mHttpClient = createHttpClient();
        List<NameValuePair> postParams = new ArrayList<>();
        //要传递的参数
        postParams.add(new BasicNameValuePair("username", "moon"));
        postParams.add(new BasicNameValuePair("password", "999"));
        mHttpPost.setEntity(new UrlEncodedFormEntity(postParams));
        HttpResponse mHttpResponse = mHttpClient.execute(mHttpPost);
        HttpEntity mHttpEntity = mHttpResponse.getEntity();
        int code = mHttpResponse.getStatusLine().getStatusCode();
        if (null != mHttpEntity) {
            InputStream mInputStream = mHttpEntity.getContent();
            String respose = converStreamToString(mInputStream);
            Log.i("wangshu", "请求状态码:" + code + "\n请求结果:\n" + respose);
            mInputStream.close();
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

2.HttpURLConnection

Android 2.2版本之前，HttpURLConnection一直存在着一些令人厌烦的bug。比如说对一个可读的InputStream调用close()方法时，就有可能会导致连接池失效了。那么我们通常的解决办法就是直接禁用掉连接池的功能：

 private void disableConnectionReuseIfNecessary() {
      // 这是一个2.2版本之前的bug
      if (Integer.parseInt(Build.VERSION.SDK) < Build.VERSION_CODES.FROYO) {
            System.setProperty("http.keepAlive", "false");
      }
}

所以在Android 2.2版本以及之前的版本使用HttpClient是较好的选择，而在Android 2.3版本及以后，HttpURLConnection则是最佳的选择，它的API简单，体积较小，因而非常适用于Android项目。压缩和缓存机制可以有效地减少网络访问的流量，在提升速度和省电方面也起到了较大的作用。另外在Android 6.0版本中，HttpClient库被移除了，HttpURLConnection则是以后我们唯一的选择。

HttpURLConnection的POST请求

因为会了HttpURLConnection的POST请求那GET请求也就会了，所以我这里只举出POST的例子
首先我们创建一个UrlConnManager类，然后里面提供getHttpURLConnection()方法用于配置默认的参数并返回HttpURLConnection：

 public static HttpURLConnection getHttpURLConnection(String url){
     HttpURLConnection mHttpURLConnection=null;
     try {
         URL mUrl=new URL(url);
         mHttpURLConnection=(HttpURLConnection)mUrl.openConnection();
         //设置链接超时时间
         mHttpURLConnection.setConnectTimeout(15000);
         //设置读取超时时间
         mHttpURLConnection.setReadTimeout(15000);
         //设置请求参数
         mHttpURLConnection.setRequestMethod("POST");
         //添加Header
         mHttpURLConnection.setRequestProperty("Connection","Keep-Alive");
         //接收输入流
         mHttpURLConnection.setDoInput(true);
         //传递参数时需要开启
         mHttpURLConnection.setDoOutput(true);
     } catch (IOException e) {
         e.printStackTrace();
     }
     return mHttpURLConnection ;
 }

因为我们要发送POST请求，所以在UrlConnManager类中再写一个postParams()方法用来组织一下请求参数并将请求参数写入到输出流中：

 public static void postParams(OutputStream output,List<NameValuePair>paramsList) throws IOException{
      StringBuilder mStringBuilder=new StringBuilder();
      for (NameValuePair pair:paramsList){
          if(!TextUtils.isEmpty(mStringBuilder)){
              mStringBuilder.append("&");
          }
          mStringBuilder.append(URLEncoder.encode(pair.getName(),"UTF-8"));
          mStringBuilder.append("=");
          mStringBuilder.append(URLEncoder.encode(pair.getValue(),"UTF-8"));
      }
      BufferedWriter writer=new BufferedWriter(new OutputStreamWriter(output,"UTF-8"));
      writer.write(mStringBuilder.toString());
      writer.flush();
      writer.close();
  }

接下来我们添加请求参数，调用postParams()方法将请求的参数组织好传给HttpURLConnection的输出流，请求连接并处理返回的结果：

 private void useHttpUrlConnectionPost(String url) {
     InputStream mInputStream = null;
     HttpURLConnection mHttpURLConnection = UrlConnManager.getHttpURLConnection(url);
     try {
         List<NameValuePair> postParams = new ArrayList<>();
         //要传递的参数
         postParams.add(new BasicNameValuePair("username", "moon"));
         postParams.add(new BasicNameValuePair("password", "123"));
         UrlConnManager.postParams(mHttpURLConnection.getOutputStream(), postParams);
         mHttpURLConnection.connect();
         mInputStream = mHttpURLConnection.getInputStream();
         int code = mHttpURLConnection.getResponseCode();
         String respose = converStreamToString(mInputStream);
         Log.i("wangshu", "请求状态码:" + code + "\n请求结果:\n" + respose);
         mInputStream.close();
     } catch (IOException e) {
         e.printStackTrace();
     }
 }

最后开启线程请求网络：

 private void useHttpUrlConnectionGetThread() {
       new Thread(new Runnable() {
           @Override
           public void run() {
               useHttpUrlConnectionPost("http://www.baidu.com");
           }
       }).start();
   }

Fiddler和HTTP协议分析的请查看HTTP协议分析。