Android中使用HttpURLConnection实现GET POST JSON数据与下载图片

Android6.0中把Apache Http Client所有的包与类都标记为deprecated不再建议使用所有跟HTTP相关的数据请求与提交操作都通过HttpURLConnection类实现，现实是很多Android开发者一直都Apache HTTP Client来做andoird客户端与后台HTTP接口数据交互，小编刚刚用HttpURLConnection做了一个android的APP，不小心踩到了几个坑，总结下最常用的就通过HttpURLConnection来POST提交JSON数据与GET请求JSON数据。此外就是下载图片，下载图片分为显示进度与不显示进度两种。其中提交数据的时候涉及中文一定要先把中文转码成utf-8之后在POST提交，否则就会一直遇到HTTP 400的错误。

一、GET请求JSON数据的例子

public UserDto execute(String... params) { 
 InputStream inputStream = null; 
 HttpURLConnection urlConnection = null; 
 try { 
 // read responseURLEncoder.encode(para, "GBK"); 
 String urlWithParams = DOMaiN_ADDRESS + MEMBER_REQUEST_TOKEN_URL + "?userName=" + java.net.URLEncoder.encode(params[0],"utf-8") + "&passWord=" + params[1]; 
 URL url = new URL(urlWithParams); 
 urlConnection = (HttpURLConnection) url.openConnection(); 
  
 urlConnection.setRequestProperty("Content-Type", "application/JSON; charset=UTF-8"); 
  
 urlConnection.setRequestProperty("Accept", "application/json"); 
  
 urlConnection.setRequestMethod("GET"); 
 int statusCode = urlConnection.getResponseCode(); 
  
 if (statusCode == 200) { 
  inputStream = new BufferedInputStream(urlConnection.getInputStream()); 
  String response = HttpUtil.convertInputStreamToString(inputStream); 
  Gson gson = new Gson(); 
  UserDto dto = gson.fromJson(response, UserDto.class); 
  if (dto != null && dto.getToken() != null) { 
  Log.i("token", "find the token = " + dto.getToken()); 
  } 
  return dto; 
 } 
 } catch (Exception e) { 
 e.printStackTrace(); 
 } finally { 
 if (inputStream != null) { 
  try { 
  inputStream.close(); 
  } catch (IOException e) { 
  e.printStackTrace(); 
  } 
 } 
 if (urlConnection != null) { 
  urlConnection.disconnect(); 
 } 
 } 
 return null; 
} 

二、POST提交JSON数据

public Map<String, String> execute(NotificationDto dto) { 
 InputStream inputStream = null; 
 HttpURLConnection urlConnection = null; 
 try { 
 URL url = new URL(getUrl); 
 urlConnection = (HttpURLConnection) url.openConnection(); 
  
 urlConnection.setRequestProperty("Content-Type", "application/json; charset=UTF-8"); 
  
 urlConnection.setRequestProperty("Accept", "application/json"); 
 dto.setCreator(java.net.URLEncoder.encode(dto.getCreator(), "utf-8")); 
 // read response 
  
 urlConnection.setRequestMethod("POST"); 
 urlConnection.setDoOutput(true); 
 DataOutputStream wr = new DataOutputStream(urlConnection.getOutputStream()); 
 Gson gson = new Gson(); 
 String jsonString = gson.toJson(dto); 
 wr.writeBytes(jsonString); 
 wr.flush(); 
 wr.close(); 
 // try to get response 
 int statusCode = urlConnection.getResponseCode(); 
 if (statusCode == 200) { 
  inputStream = new BufferedInputStream(urlConnection.getInputStream()); 
  String response = HttpUtil.convertInputStreamToString(inputStream); 
  Map<String, String> resultMap = gson.fromJson(response, Map.class); 
  if (resultMap != null && resultMap.size() > 0) { 
  Log.i("applyDesigner", "please check the map with key"); 
  } 
  return resultMap; 
 } 
 } 
 catch(Exception e) 
 { 
 e.printStackTrace(); 
 } 
 finally 
 { 
 if (inputStream != null) { 
  try { 
  inputStream.close(); 
  } catch (IOException e) { 
  e.printStackTrace(); 
  } 
 } 
 if (urlConnection != null) { 
  urlConnection.disconnect(); 
 } 
 } 
 return null; 
} 

三、下载图片显示下载进度

package com.example.demo; 
import java.io.ByteArrayInputStream; 
import java.io.ByteArrayOutputStream; 
import java.io.IOException; 
import java.io.InputStream; 
import java.net.HttpURLConnection; 
import java.net.URL; 
import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
import android.os.AsyncTask; 
import android.os.Handler; 
import android.os.Message; 
import android.util.Log; 
public class ImageLoadTask extends AsyncTask<String, Void, Bitmap> { 
 private Handler handler; 
 public ImageLoadTask(Handler handler) { 
 this.handler = handler; 
 } 
 protected void onPostExecute(Bitmap result) { 
 Message msg = new Message(); 
 msg.obj = result; 
 handler.sendMessage(msg); 
 } 
 protected Bitmap doInBackground(String... getUrls) { 
 InputStream inputStream = null; 
 HttpURLConnection urlConnection = null; 
 try { 
  // open connection 
  URL url = new URL(getUrls[0]); 
  urlConnection = (HttpURLConnection) url.openConnection(); 
   
  urlConnection.setRequestMethod("GET"); 
  int fileLength = urlConnection.getContentLength(); 
  int statusCode = urlConnection.getResponseCode(); 
  if (statusCode == 200) { 
  inputStream = urlConnection.getInputStream(); 
  byte data[] = new byte[4096]; 
  long total = 0; 
  int count; 
  ByteArrayOutputStream output = new ByteArrayOutputStream(); 
  while ((count = inputStream.read(data)) != -1) { 
   total += count; 
   // publishing the progress.... 
   if (fileLength > 0 && handler != null) { 
   handler.sendEmptyMessage(((int) (total * 100 / fileLength)) - 1); 
   } 
   output.write(data, 0, count); 
  } 
  ByteArrayInputStream bufferInput = new ByteArrayInputStream(output.toByteArray()); 
  Bitmap bitmap = BitmapFactory.decodeStream(bufferInput); 
  inputStream.close(); 
  bufferInput.close(); 
  output.close(); 
  Log.i("image", "already get the image by uuid : " + getUrls[0]); 
  handler.sendEmptyMessage(100); 
  return bitmap; 
  } 
 } catch (Exception e) { 
  e.printStackTrace(); 
 } finally { 
  if (inputStream != null) { 
  try { 
   inputStream.close(); 
  } catch (IOException e) { 
   e.printStackTrace(); 
  } 
  } 
  if (urlConnection != null) { 
  urlConnection.disconnect(); 
  } 
 } 
 return null; 
 } 
} 

总结：使用HttpURLConnection提交JSON数据的时候编码方式为UTF-8所有中文字符请一定要预先转码为UTF-8，然后在后台服务器对应的api中解码为UTF-8，不然就会报错HTTP 400。

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