从 Android 调用 Java servlet
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【中文标题】从 Android 调用 Java servlet【英文标题】：Call Java servlet from Android 【发布时间】：2011-03-16 10:42:30 【问题描述】：我正在尝试从 android 手机上的 servlet 获取输出。
这是我的 servlet：
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package main;
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;
/**
*
* @author Bert Verhelst <verhelst_bert@hotmail.com>
*/
public class servlet1 extends HttpServlet
/**
* Processes requests for both HTTP <code>GET</code> and <code>POST</code> methods.
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
out.println("<html>");
out.println("<head>");
out.println("<title>Servlet servlet1</title>");
out.println("</head>");
out.println("<body>");
out.println("<h1>processing...</h1>");
out.println("</body>");
out.println("</html>");
// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
/**
* Handles the HTTP <code>GET</code> method.
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
processRequest(request, response);
PrintWriter out = response.getWriter();
out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.0 "
+ "Transitional//EN\">\n"
+ "<html>\n"
+ "<head><title>Hello WWW</title></head>\n"
+ "<body>\n"
+ "<h1>doget...</h1>\n"
+ "</body></html>");
/**
* Handles the HTTP <code>POST</code> method.
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
processRequest(request, response);
PrintWriter out = response.getWriter();
out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.0 "
+ "Transitional//EN\">\n"
+ "<html>\n"
+ "<head><title>Hello WWW</title></head>\n"
+ "<body>\n"
+ "<h1>dopost...</h1>\n"
+ "</body></html>");
/**
* Returns a short description of the servlet.
* @return a String containing servlet description
*/
@Override
public String getServletInfo()
return "Short description";
// </editor-fold>
这是我的 Android 主页：
package be.smarttelecom.MyTest;
import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;
public class Main extends Activity
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
TextView output = (TextView) findViewById(R.id.output);
try
output.append("starting\n");
RestClient client = new RestClient("http://10.0.0.188:8084/Servlet_1/servlet1");
try
client.Execute(RequestMethod.GET);
catch (Exception e)
e.printStackTrace();
output.append("after execute\n");
String response = client.getResponse();
output.append("class - " + response + "\n" );
output.append(response);
output.append("done\n");
catch (Exception ex)
output.append("error: " + ex.getMessage() + "\n" + ex.toString() + "\n");
最后我们有了 RestClient：
package be.smarttelecom.MyTest;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.methods.HttpUriRequest;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.protocol.HTTP;
public class RestClient
private ArrayList <NameValuePair> params;
private ArrayList <NameValuePair> headers;
private String url;
private int responseCode;
private String message;
private String response;
public String getResponse()
return response;
public String getErrorMessage()
return message;
public int getResponseCode()
return responseCode;
public RestClient(String url)
this.url = url;
params = new ArrayList<NameValuePair>();
headers = new ArrayList<NameValuePair>();
public void AddParam(String name, String value)
params.add(new BasicNameValuePair(name, value));
public void AddHeader(String name, String value)
headers.add(new BasicNameValuePair(name, value));
public void Execute(RequestMethod method) throws Exception
switch(method)
case GET:
//add parameters
String combinedParams = "";
if(!params.isEmpty())
combinedParams += "?";
for(NameValuePair p : params)
String paramString = p.getName() + "=" + p.getValue();
if(combinedParams.length() > 1)
combinedParams += "&" + paramString;
else
combinedParams += paramString;
HttpGet request = new HttpGet(url + combinedParams);
//add headers
for(NameValuePair h : headers)
request.addHeader(h.getName(), h.getValue());
executeRequest(request, url);
break;
case POST:
HttpPost request = new HttpPost(url);
//add headers
for(NameValuePair h : headers)
request.addHeader(h.getName(), h.getValue());
if(!params.isEmpty())
request.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));
executeRequest(request, url);
break;
private void executeRequest(HttpUriRequest request, String url)
HttpClient client = new DefaultHttpClient();
HttpResponse httpResponse;
try
httpResponse = client.execute(request);
responseCode = httpResponse.getStatusLine().getStatusCode();
message = httpResponse.getStatusLine().getReasonPhrase();
HttpEntity entity = httpResponse.getEntity();
if (entity != null)
InputStream instream = entity.getContent();
response = convertStreamToString(instream);
// Closing the input stream will trigger connection release
instream.close();
catch (ClientProtocolException e)
client.getConnectionManager().shutdown();
e.printStackTrace();
catch (IOException e)
client.getConnectionManager().shutdown();
e.printStackTrace();
private static String convertStreamToString(InputStream is)
BufferedReader reader = new BufferedReader(new InputStreamReader(is));
StringBuilder sb = new StringBuilder();
String line = null;
try
while ((line = reader.readLine()) != null)
sb.append(line + "\n");
catch (IOException e)
e.printStackTrace();
finally
try
is.close();
catch (IOException e)
e.printStackTrace();
return sb.toString();
不幸的是，这不起作用。这是我得到的输出（null），
我做错了什么？
我请求我的 servlet 的 DoGet 方法并将输出转换为字符串，但它似乎是空的。
我在应用程序右括号之后的清单文件中允许互联网连接，
<uses-permission android:name="android.permission.INTERNET" />
【问题讨论】：
如果您从浏览器访问 servlet，您会得到预期的结果吗？此外，您的 doGet() 调用 processRequest，它执行 out.close()，而 doGet 尝试在关闭的流上写入更多 HTML（从不关闭 servlet 中的输出流）。 调用是否到达了 Servlet ？服务器看到正在发送什么？服务器发回什么？ 【参考方案1】：Romain Hippeau 在评论中写道：
调用是否会到达 servlet？服务器看到正在发送什么？服务器发回什么？
这就是问题所在！我禁用了我的防火墙，现在它可以工作了:)
【讨论】：
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