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Android应用程序中显示相同的消息，该应用程序在另一个系统中运行。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<String, Void, String> {
@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网络中帮助真的非常感激。在此先感谢所有
答案 0 :(得分：2)
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<NameValuePair> postParameters = new ArrayList<NameValuePair>();
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<NameValuePair> 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;
}}
最后这是你的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";
}}