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，本人刚刚用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(); /* optional request header */ urlConnection.setRequestProperty("Content-Type", "application/json; charset=UTF-8"); /* optional request header */ urlConnection.setRequestProperty("Accept", "application/json"); /* for Get request */ urlConnection.setRequestMethod("GET"); int statusCode = urlConnection.getResponseCode(); /* 200 represents HTTP OK */ 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(); /* optional request header */ urlConnection.setRequestProperty("Content-Type", "application/json; charset=UTF-8"); /* optional request header */ urlConnection.setRequestProperty("Accept", "application/json"); dto.setCreator(java.net.URLEncoder.encode(dto.getCreator(), "utf-8")); // read response /* for Get request */ 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(); /* for Get request */ 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。
