Android一般通过http协议向服务端接口发送请求，常用有POST和GET传输方式。这种请求通常借助于HttpClient，HttpClient 是 Apache Jakarta Common 下的子项目，可以用来提供高效的、最新的、功能丰富的支持 HTTP 协议的客户端编程工具包。通过HttpClient可以不借助浏览器，从而简化了客户端与服务器端之间的交互。
HttpPost httpPost=new HttpPost(reqUrl);
HttpResponsehttpResponse=new DefaultHttpClient().execute(httpPost);
DefaultHttpClient是HttpClient接口的默认实现，new DefaultHttpClient().execute(httpPost);则是使用一个匿名内部类来处理请求。该匿名内部类继承自DefaultHttpClient，而DefaultHttpClient实现了HttpClient接口，所有可以重写HttpClient接口下execute的方法来处理请求。
AndroidPost请求的两种方式
(1)、HttpPost
HttpPost httpRequest =new HttpPost(url);List <NameValuePair> params=new ArrayList<NameValuePair>();//Post方式用NameValuePair[]阵列储存params.add(new BasicNameValuePair("name","name"));try{ //设置请求参数httpRequest.setEntity(new UrlEncodedFormEntity(params,HTTP.UTF_8));//创建HttpClient实例HttpClient client = new DefaultHttpClient();//请求超时client.getParams().setParameter(CoreConnectionPNames.CONNECTION_TIMEOUT, 20000);//读取超时client.getParams().setParameter(CoreConnectionPNames.SO_TIMEOUT, 20000 );//取得HTTP responseHttpResponse httpResponse = client.execute(httpRequest);//若状态码为200 ok if(httpResponse.getStatusLine().getStatusCode()==200){//取出回应字串String strResult=EntityUtils.toString(httpResponse.getEntity());}else{;}}catch(ClientProtocolException e){Toast.makeText(getApplicationContext(), e.getMessage().toString(),Toast.LENGTH_SHORT).show();e.printStackTrace();} catch (UnsupportedEncodingException e) {Toast.makeText(getApplicationContext(), e.getMessage().toString(),Toast.LENGTH_SHORT).show();e.printStackTrace();} catch (IOException e) {Toast.makeText(getApplicationContext(), e.getMessage().toString(),Toast.LENGTH_SHORT).show();e.printStackTrace();}
(2)、HttpURLConnection
try{
//建立连接
URL url=new URL(url);
HttpURLConnection httpConn=(HttpURLConnection)url.openConnection();
设置连接属性
httpConn.setDoOutput(true);//使用 URL 连接进行输出
httpConn.setDoInput(true);//使用 URL 连接进行输入
httpConn.setUseCaches(false);//忽略缓存
httpConn.setRequestMethod("POST");//设置URL请求方法
String requestString = "客服端要以以流方式发送到服务端的数据...";
//设置请求属性
//获得数据字节数据，请求数据流的编码，必须和下面服务器端处理请求流的编码一致
byte[] requestStringBytes = requestString.getBytes("utf-8");
httpConn.setRequestProperty("Content-length", "" + requestStringBytes.length);
httpConn.setRequestProperty("Content-Type", "application/octet-stream");
httpConn.setRequestProperty("Connection", "Keep-Alive");// 维持长连接
httpConn.setRequestProperty("Charset", "UTF-8");
//
String name=URLEncoder.encode("张三","utf-8");
httpConn.setRequestProperty("name", name);
//建立输出流，并写入数据
OutputStream outputStream = httpConn.getOutputStream();
outputStream.write(requestStringBytes);
outputStream.close();
//获得响应状态
int responseCode = httpConn.getResponseCode();
if(HttpURLConnection.HTTP_OK == responseCode){//连接成功
//当正确响应时处理数据
StringBuffer sb = new StringBuffer();
String readLine;
BufferedReader responseReader;
//处理响应流，必须与服务器响应流输出的编码一致
responseReader = new BufferedReader(new InputStreamReader(httpConn.getInputStream(), ENCODING_UTF_8));
while ((readLine = responseReader.readLine()) != null) {
sb.append(readLine).append("\n");
}
responseReader.close();
}
}catch(Exception ex){
ex.printStackTrace();
}
HttpClient和HttpURLConnection是访问HTTP的两种方式，
HttpURLConnection是一个抽象类，继承自URLConnection抽象类，基于标准Java接口()，可以实现简单的基于URL请求、响应功能；HttpClient基于Apache接口(org.appache.http)，使用起来更方面更强大。一般来说，使用这种接口比较多。运用这两种方式，android可以访问网页、下载图片或文件、上传文件，甚至参数配置适当时，可以抓取服务器的很多数据。如用android做多图上传到服务器。
首先我们先解析目标url请求时的一些参数
如提请求的url地址Request URL，提交的方式Request Method，服务器端的IP地址及端口Remote Address，请求头RequestHeaders，请求负载（表单参数）Request Payload,进而我们就可以在代码里面进行设置，然后发送请求
/*** 解析multipart/form-data方式提交的请求，并以同样的方式再提交*/@SuppressWarnings("unchecked")public static HttpURLConnection doPostMultipartFormData(.URL url,MultipartHttpServletRequest request){//分割字符串String BOUNDARY = UUIDTool.getUUID().toUpperCase();String BOUNDARYSP = "--";String BOUNDARYSTR = BOUNDARYSP + BOUNDARY;String LINESP = "\r\n";HttpURLConnection conn = null;try{conn = (HttpURLConnection) url.openConnection();conn.setUseCaches(false);conn.setDoOutput(true);// 是否输入参数conn.setConnectTimeout(3000);conn.setRequestMethod("POST");conn.setRequestProperty("Accept","text/html, application/xhtml+xml, */*");conn.setRequestProperty("Accept-Language", "zh-CN");conn.setRequestProperty("User-Agent","Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.2; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)");conn.setRequestProperty("Connection", "Keep-Alive");conn.setRequestProperty("Accept-Charset", "UTF-8");//conn.setRequestProperty("contentType", "UTF-8");conn.setRequestProperty("Content-Type","multipart/form-data; boundary=" + BOUNDARY+"; charset=UTF-8");OutputStream out = new DataOutputStream(conn.getOutputStream()); //byte[] end_data = ("\r\n--" + BOUNDARY + "--\r\n").getBytes();// 定义最后数据分隔线 StringBuffer multiParamsData = new StringBuffer();//组装普通参数Map params = request.getParameterMap();for(Object key : params.keySet()){Object paramvalue = params.get(key);if(paramvalue!=null){if(paramvalue instanceof String[]){for(String param : (String[])paramvalue){multiParamsData.append(BOUNDARYSTR);multiParamsData.append(LINESP);multiParamsData.append("Content-Disposition: form-data; name=\""+key+"\"");multiParamsData.append(LINESP);multiParamsData.append("Content-Type: text/plain; charset=UTF-8");multiParamsData.append(LINESP);multiParamsData.append(LINESP);multiParamsData.append(param);multiParamsData.append(LINESP);}}else{multiParamsData.append(BOUNDARYSTR);multiParamsData.append(LINESP);multiParamsData.append("Content-Disposition: form-data; name=\""+key+"\"");multiParamsData.append(LINESP);multiParamsData.append("Content-Type: text/plain; charset=UTF-8");multiParamsData.append(LINESP);multiParamsData.append(LINESP);multiParamsData.append(paramvalue);multiParamsData.append(LINESP);}}}//System.out.println(multiParamsData.toString());out.write(multiParamsData.toString().getBytes("UTF-8"));//组装文件Map<String, MultipartFile> files = request.getFileMap();int i = 1;for(String key : files.keySet()){StringBuffer multiFilesData = new StringBuffer();MultipartFile multipartFile = files.get(key);multiFilesData.append(BOUNDARYSTR);multiFilesData.append(LINESP);multiFilesData.append("Content-Disposition: form-data; name=\""+key+"\"; filename=\""+multipartFile.getOriginalFilename()+"\"");multiFilesData.append(LINESP);multiFilesData.append("Content-Type:application/octet-stream");multiFilesData.append(LINESP);multiFilesData.append(LINESP);//multiData.append(paramvalue);out.write(multiFilesData.toString().getBytes("UTF-8"));DataInputStream in = new DataInputStream(multipartFile.getInputStream()); int bytes = 0; byte[] bufferOut = new byte[1024]; while ((bytes = in.read(bufferOut)) != -1) { out.write(bufferOut, 0, bytes); } out.write(LINESP.getBytes("UTF-8"));in.close();// System.out.println(multiFilesData.toString()+"<file content; length:"+readStream(multipartFile.getInputStream()).length+">");}//System.out.println(BOUNDARYSTR+BOUNDARYSP);out.write((BOUNDARYSTR+BOUNDARYSP+LINESP).getBytes("UTF-8")); out.flush(); out.close(); //byte[] bypes = params.getBytes("UTF-8");//System.out.println("2>>>>>>"+new String(params,"UTF-8"));//conn.getOutputStream().write(params);}catch(ConnectException e){}catch(Exception e){logger.error("HttpRequest Error:",e);}return conn;}
HttpPsot结合Handle
new Thread(new Runnable() {@Overridepublic void run() {// TODO Auto-generated method stubMessage message=new Message();HttpPost httpPost=new HttpPost(reqUrl);try{httpPost.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));HttpResponse httpResponse;try{httpResponse=new DefaultHttpClient().execute(httpPost);if(httpResponse.getStatusLine().getStatusCode()==200){String result = EntityUtils.toString(httpResponse.getEntity());if(!result.isEmpty()){message.what=0;message.obj=result;myHandler.sendMessage(message);}else{message.what=1;myHandler.sendMessage(message);}}else{message.what=1;myHandler.sendMessage(message);}}catch(Exception e){e.printStackTrace();}}catch(Exception e){e.printStackTrace();}}}).start();
static Handler myHandler=new Handler(){@Overridepublic void handleMessage(android.os.Message msg) {if(msg.what==1){resultCallback.getReslt("1");}else if(msg.what==0){String result=(String) msg.obj;}};};
涉及到网络数据传输，AndroidManifest.xml中要设置相应的权限。
<uses-permission android:name="android.permission.INTERNET" />
同时可以对网络状态做一些相应的处理。
/** * 检测网络是否连接* @return */ private boolean isNetConnected() { ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE); if (cm != null) { NetworkInfo[] infos = cm.getAllNetworkInfo(); if (infos != null) { for (NetworkInfo ni : infos) { if (ni.isConnected()) { return true; } } } } return false; } /*** 设置网络* @param context*/private void isNetworkAvailable(Context context) {new AlertDialog.Builder(LoginActivity.this).setTitle("网络设置提示").setMessage("网络不可用，是否现在设置网络？").setPositiveButton("设置",new DialogInterface.OnClickListener() {@Overridepublic void onClick(DialogInterface dialog,int which) {if(android.os.Build.VERSION.SDK_INT > 10 ){//3.0以上打开设置界面，也可以直接用ACTION_WIRELESS_SETTINGS打开到wifi界面startActivity(new Intent(android.provider.Settings.ACTION_SETTINGS));} else {startActivity(new Intent(android.provider.Settings.ACTION_WIRELESS_SETTINGS));}overridePendingTransition(R.anim.push_left_in, R.anim.push_left_out);}}).setNegativeButton("取消", null).show();
