如何将数据从java servlet发送到Android客户端

Question

我正在做一个简单的android应用程序。 Android应用程序有一个简单的表单，当我从Android客户端单击提交按钮时，表单值将转到servlet。现在我有一个问题，从servlet获取字符串值到Android客户端。

如何从servlet发送字符串数据？我怎样才能在Android客户端接收字符串数据？

Answer 1

您需要对您的servlet页面进行URLConnection并执行此操作。举例吧：http://www.helloandroid.com/tutorials/how-download-fileimage-url-your-device

Answer 2

另存为以下CustomHttpClient.java

import java.io.BufferedReader; 
import java.io.IOException; 
import java.io.InputStreamReader; 
import java.net.URI; 
import java.util.ArrayList; 

import org.apache.http.HttpResponse; 
import org.apache.http.NameValuePair; 
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.conn.params.ConnManagerParams; 
import org.apache.http.impl.client.DefaultHttpClient; 
import org.apache.http.params.HttpConnectionParams; 
import org.apache.http.params.HttpParams; 

public class CustomHttpClient { 
    /** 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); 
      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(); 

      String result = sb.toString(); 
      return result; 
     } finally { 
      if (in != null) { 
       try { 
        in.close(); 
       } catch (IOException e) { 
        e.printStackTrace(); 
       } 
      } 
     } 
    } 

    /** 
    * 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 { 
     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(); 

      String result = sb.toString(); 
      return result; 
     } finally { 
      if (in != null) { 
       try { 
        in.close(); 
       } catch (IOException e) { 
        e.printStackTrace(); 
       } 
      } 
     } 
    } 
} 

现在要使客户端服务器通信的代码添加代码

ArrayList<NameValuePair> postParameters = new ArrayList<NameValuePair>(); 
      postParameters.add(new BasicNameValuePair("username",str2)); 

//here we are passing a variable str2 to the server. 
      String response = null; 
try { 

//address should be the http address of the server side code. 
        response = CustomHttpClient.executeHttpPost("http://www.xxx.xx/xxx.java", postParameters); 
         String res=response.toString(); 
         res= res.replaceAll("\\s+",""); 


        //res will be the string that you get from the server.