在android Application和java之间进行通信
每个身体我是程序世界的新手，我遇到了问题，我的请求与使用JAVA Code的Android平板电脑与台式PC之间的通信有关。
import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class HelloWorldServlet extends HttpServlet { private static final long serialVersionUID = 1L; public HelloWorldServlet() { super(); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { PrintWriter out = response.getWriter(); out.println("Hello Android !!!!"); } } 上面的代码是我的servlet代码，它在我的本地系统服务器（Tomcat 6.0）中运行，我在这里通过println发送消息，我想在我的另一个系统中运行的Android应用程序中显示相同的消息。 现在我要发布我在另一个系统上运行的android代码。
import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.net.HttpURLConnection; import java.net.URL; import java.net.URLConnection; import android.app.Activity; import android.os.AsyncTask; import android.os.Bundle; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.TextView; public class HttpGetServletActivity3 extends Activity implements OnClickListener { Button button; TextView outputText; public static final String URL = "http://192.168.0.2:9999/HttpGetServlet/HelloWorldServlet"; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); findViewsById(); button.setOnClickListener(this); } private void findViewsById() { button = (Button) findViewById(R.id.button); outputText = (TextView) findViewById(R.id.outputTxt); } public void onClick(View view) { GetXMLTask task = new GetXMLTask(); task.execute(new String[] { URL }); } private class GetXMLTask extends AsyncTask { @Override protected String doInBackground(String... urls) { String output = null; for (String url : urls) { output = getOutputFromUrl(url); } return output; } private String getOutputFromUrl(String url) { StringBuffer output = new StringBuffer(""); try { InputStream stream = getHttpConnection(url); BufferedReader buffer = new BufferedReader( new InputStreamReader(stream)); String s = ""; while ((s = buffer.readLine()) != null) output.append(s); } catch (IOException e1) { e1.printStackTrace(); } return output.toString(); } // Makes HttpURLConnection and returns InputStream private InputStream getHttpConnection(String urlString) throws IOException { InputStream stream = null; URL url = new URL(urlString); URLConnection connection = url.openConnection(); try { HttpURLConnection httpConnection = (HttpURLConnection) connection; httpConnection.setRequestMethod("GET"); httpConnection.connect(); if (httpConnection.getResponseCode() == HttpURLConnection.HTTP_OK) { stream = httpConnection.getInputStream(); } } catch (Exception ex) { ex.printStackTrace(); } return stream; } @Override protected void onPostExecute(String output) { outputText.setText(output); } }}
这里192.68.0.2是系统的ip地址，其中servlet代码在我的本地系统中运行（Tomcat6.0服务器，端口号为9999）。但它对我不起作用。系统在同一个wifi网络中任何帮助都是真的非常感激。 在此先感谢所有人
试试这个我会为你工作。 这是android代码
protected Integer doInBackground(String... arg0) { /** According with the new StrictGuard policy, running long tasks on the Main UI thread is not possible So creating new thread to create and execute http operations */ new Thread(new Runnable() { @Override public void run() { ArrayList postParameters = new ArrayList (); postParameters.add(new BasicNameValuePair("username",un.getText().toString())); postParameters.add(new BasicNameValuePair("password",pw.getText().toString())); String response = null; try { response = SimpleHttpClient.executeHttpPost("http://XXX.168.1.X:5555/LoginServlet/loginservlet.do", postParameters); res = response.toString(); System.out.println("response :"+res); } catch (Exception e) { // e.printStackTrace(); errorMsg = e.getMessage(); } } }).start(); /** Inside the new thread we cannot update the main thread So updating the main thread outside the new thread */ try { }catch (Exception e) { error.setText(e.getMessage()); // e.printStackTrace(); } return null; }
现在这是android的另一个类
public class SimpleHttpClient { public static String result=""; /** The time it takes for our client to timeout */ public static final int HTTP_TIMEOUT = 30 * 1000; // milliseconds /** Single instance of our HttpClient */ private static HttpClient mHttpClient; /** * Get our single instance of our HttpClient object. * * @return an HttpClient object with connection parameters set */ private static HttpClient getHttpClient() { if (mHttpClient == null) { mHttpClient = new DefaultHttpClient(); final HttpParams params = mHttpClient.getParams(); HttpConnectionParams.setConnectionTimeout(params, HTTP_TIMEOUT); HttpConnectionParams.setSoTimeout(params, HTTP_TIMEOUT); ConnManagerParams.setTimeout(params, HTTP_TIMEOUT); } return mHttpClient; } /** * Performs an HTTP Post request to the specified url with the * specified parameters. * * @param url The web address to post the request to * @param postParameters The parameters to send via the request * @return The result of the request * @throws Exception */ public static String executeHttpPost(String url, ArrayList postParameters) throws Exception { BufferedReader in = null; try { HttpClient client = getHttpClient(); HttpPost request = new HttpPost(url); UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(postParameters); request.setEntity(formEntity); // String str1= request.setEntity(formEntity); System.out.println("actual request"+formEntity); HttpResponse response = client.execute(request); System.out.println("response in class"+response); in = new BufferedReader(new InputStreamReader(response.getEntity().getContent())); StringBuffer sb = new StringBuffer(""); String line = ""; String NL = System.getProperty("line.separator"); while ((line = in.readLine()) != null) { sb.append(line + NL); } in.close(); result = sb.toString(); }catch(Exception e){ e.printStackTrace(); System.out.println("catch"); } finally { if (in != null) { try { in.close(); } catch (IOException e) { e.printStackTrace(); } } } return result; } /** * Performs an HTTP GET request to the specified url. * * @param url The web address to post the request to * @return The result of the request * @throws Exception */ public static String executeHttpGet(String url) throws Exception { String result=""; BufferedReader in = null; try { HttpClient client = getHttpClient(); HttpGet request = new HttpGet(); request.setURI(new URI(url)); HttpResponse response = client.execute(request); in = new BufferedReader(new InputStreamReader(response.getEntity().getContent())); StringBuffer sb = new StringBuffer(""); String line = ""; String NL = System.getProperty("line.separator"); while ((line = in.readLine()) != null) { sb.append(line + NL); } in.close(); result = sb.toString(); } catch(Exception e){ e.printStackTrace(); System.out.println("catch2"); } finally { if (in != null) { try { in.close(); } catch (IOException e) { e.printStackTrace(); } } } return result; }}
最后这是servlet代码
public class LoginServlet extends HttpServlet { protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); try { String un,pw; un=request.getParameter("username"); pw=request.getParameter("password"); System.out.println("username :"+un); System.out.println("password :"+pw); if(un.equals("") || pw.equals("") ){ out.print("null"); } else if(un.equalsIgnoreCase("hello") && pw.equals("world")) { out.print("success"); } else{ out.print("failed"); } System.out.println("after :"); request.getAttribute("USER"+un); request.getAttribute("PASS"+pw); RequestDispatcher rd=request.getRequestDispatcher("home.jsp"); rd.forward(request, response); }catch(Exception e){ System.out.println("inside exception"); e.printStackTrace(); } finally { out.close(); } } @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { service(request, response); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { service(request, response); } @Override public String getServletInfo() { return "Short description"; }}