Android应用层（网络编程）二（HttpClient、HttpURLConnection）

HttpClient与HttpURLConnection

1.HttpClient

Android SDK中包含了HttpClient，在Android6.0版本直接删除了HttpClient类库，如果仍想使用则解决方法是：
- 如果使用的是eclipse则在libs中加入org.apache.http.legacy.jar这个jar包在：**sdk\platforms\android-23\optional目录中（需要下载android
6.0的SDK）
- 如果使用的是android studio则 在相应的module下的build.gradle中加入：

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

1.1 HttpClient的GET请求

Step 1 : 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, 15000);       //设置请求超时       HttpConnectionParams.setSoTimeout(mDefaultHttpParams, 15000);       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;   }

Step 2 : 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();

1.2 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", "123"));        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

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。

2.1 HttpURLConnection的POST请求

Step 1 : 创建一个UrlConnManager类，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 ; } ```#### Step 2 : 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();  }

Step 3 : 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();     } }

Step 4 : 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();   }

报504错误，读取响应的数据报错，对于我们这次请求服务端不能返回完整的响应，返回的数据为0 bytes，所以mHttpURLConnection.getInputStream() 也读不到服务端响应的输入流。当然这次错误是正常的，百度没理由处理我们的这次POST请求。