[Android]将参数发送到servlet

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块引用

我对Client-Server编程完全陌生，而且我遇到很多问题。 我应该从客户端android应用程序向名为＆＃34; selector＆＃34;的java servlet发送一个参数。 servlet使用getParameter方法，获得名称为＆＃34; selector＆＃34;的变量。并将一系列JSONObjects发送到Android客户端。 不幸的是，我的应用程序一直在崩溃。

这是我的Servlet代码

public class FeedServlet extends HttpServlet {
public URLGetter urlgetter;
public XMLParser xmlparser;
public URL page_url, page_feed;
public String siteName, selector, siteDescription;


protected void processRequest(HttpServletRequest request, HttpServletResponse response, NodeList nList)
        throws ServletException, IOException {
    //do nothing
}

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    selector=request.getParameter("selector");
    setWebSiteParam(request,response);//this method reads the selector and
                                      //chooses what to send back to the client
        try {
        xmlparser=new XMLParser(page_feed);//parses the RSS Feed the client requested
        NodeList nodeList=xmlparser.getNodeList();
        processRequest(request, response, nodeList);
    } catch (ParserConfigurationException | SAXException ex) {
        Logger.getLogger(FeedServlet.class.getName()).log(Level.SEVERE, null, ex);
    }
}
protected void processRequest(HttpServletRequest request, HttpServletResponse response, NodeList nList)
        throws ServletException, IOException {
    response.setContentType("application/json");
    String title,description,link;
    JSONObject dataObj=new JSONObject();
    try (PrintWriter out = response.getWriter()) {
        for (int i = 0; i < nList.getLength(); i++) {
            //Parsing the NodeList
            Node node=nList.item(i);
            Element nodeElement=(Element)node;
            title=nodeElement.getElementsByTagName("title").item(0).getTextContent();
            description=nodeElement.getElementsByTagName("description").item(0).getTextContent();
            link=nodeElement.getElementsByTagName("link").item(0).getTextContent();
            description=lengthCorrector(description);
            dataObj.put("description", description);
            dataObj.put("title", title);
            dataObj.put("link",link);
            out.println(dataObj);
        }
    } catch (JSONException ex) {
        Logger.getLogger(FeedServletMobile.class.getName()).log(Level.SEVERE, null, ex);
    }
 }
}

这是我的Android活动代码

public class ShowNews扩展了AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_show_news);
    String buttonId = this.getIntent().getStringExtra("buttonId");
    String newsType = this.getIntent().getStringExtra("newsType");
    TextView textViewNews = (TextView) findViewById(R.id.textView4);
    if (newsType != null) {
        textViewNews.setText(newsType);
    }
    TextView textViewFullcontent=(TextView) findViewById(R.id.textView5);
    Downloader download = new Downloader();
    download.execute(buttonId);

}
 private class Downloader extends AsyncTask<String, Void, String> {

    @Override
    protected String doInBackground(String... params) {
        String request=params[0];
        String serverAddress = null;
        String myFeed="I failed";
        HttpsURLConnection conn=null;
        try {
            serverAddress = "http://10.0.2.2:8080/FeedServlet/FeedServletMobile?selector="+
                    request;
            URL url;
            url= new URL(serverAddress);
            conn= (HttpsURLConnection) url.openConnection();
            conn.setReadTimeout(10000);
            conn.setConnectTimeout(15000 );
            conn.setRequestMethod("GET");
            conn.setDoInput(true);
            conn.connect();
            int response = conn.getResponseCode();
            String input;
            BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            while ((input = br.readLine()) != null){
                myFeed+=input;
            }
            br.close();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (ProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally{
            conn.disconnect();
        }
        return myFeed;
    }
    protected void onPostExecute(String result){
        TextView textViewFullcontent=(TextView) findViewById(R.id.textView5);
        textViewFullcontent.setText(result);
    }
}

类下载器包含在Android活动类中，一旦打开此活动，应用程序就会在调用HttpsUrlConnection.open（）方法后崩溃。

编辑：URLEncoder.encode方法导致崩溃，但App仍然没有做任何事情。 我将myFeed字符串设置为句子＆＃34;我失败＆＃34;：连接超时并且应用程序打印＆＃34;我失败＆＃34;在我的textView

中