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Android開發18——獲取網絡資源之json數據
一、項目背景
在Android開發中有一項非常廣泛的應用：Android項目獲取另一個web項目的資源或者返回的數據。
本文獲取web項目返回的JSON數據。Android應用解析JSON比XML性能要好，但有許多項目仍然采用的是XML。
二、實例代碼
Web項目
/**
* 新聞業務類
*
* @author 徐越
*
*/
public class VideoNewsServiceImpl implements VideoNewsService
{
public List<VideoNews> readNews()
{
List<VideoNews> lst = new ArrayList<VideoNews>();
lst.add(new VideoNews(1, "喜洋洋", 20));
lst.add(new VideoNews(2, "變形金剛", 10));
lst.add(new VideoNews(3, "功夫熊貓", 20));
return lst;
}
}
/**
* 新聞Servlet
*
* @author 徐越
*
*/
public class ListServlet extends HttpServlet
{
private static final long serialVersionUID = 1L;
private VideoNewsService vs = new VideoNewsServiceImpl();
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
doPost(request, response);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
List<VideoNews> news = vs.readNews();
JSONArray jsonarr = JSONArray.fromObject(news);
response.setCharacterEncoding("UTF-8");
response.setContentType("text/plain;charset=UTF-8");
response.setHeader("Pragma", "No-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);
response.getWriter().print(jsonarr);
}
}
Android項目
public class VideoNewsServiceImpl implements VideoNewsService
{
/**
* 獲取最新視頻資訊，從JSON文件中，解析效率高
*
* @return
* @throws Exception
*/
public List<VideoNews> getNewsFromJson() throws Exception
{
List<VideoNews> lst = new ArrayList<VideoNews>();
String path = "https://xxx.xxx.xxx.xxx:8080/web/ListServlet";
URL url = new URL(path);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setReadTimeout(5000);
conn.setRequestMethod("GET");
if (200 == conn.getResponseCode())
{
InputStream instream = conn.getInputStream();
lst = parseJSON(instream);
}
return lst;
}
/**
* 解析JSON
*/
private List<VideoNews> parseJSON(InputStream instream) throws Exception
{
List<VideoNews> lst = new ArrayList<VideoNews>();
byte[] data = IOUtils.read(instream);
String jsonStr = new String(data);
JSONArray array = new JSONArray(jsonStr);
for (int i = 0; i < array.length(); i++)
{
JSONObject jsonObj = (JSONObject) array.getJSONObject(i);
VideoNews v = new VideoNews(jsonObj.getInt("id"),
jsonObj.getString("title"), jsonObj.getInt("timeLength"));
lst.add(v);
}
return lst;
}
}
/**
* IO操作工具類
*
* @author 徐越
*
*/
public class IOUtils
{
/**
* 讀取輸入流為byte[]數組
*/
public static byte[] read(InputStream instream) throws IOException
{
ByteArrayOutputStream bos = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int len = 0;
while ((len = instream.read(buffer)) != -1)
{
bos.write(buffer, 0, len);
}
return bos.toByteArray();
}
}
需要指出的是
在web項目中我采用的是net.sf.json下的類對JSON進行解析，而Android項目中默認自帶的JSON包是org.json。API有所不同，隻要熟悉一下即可。
最後更新：2017-04-03 05:40:20