java - 从 Android 应用程序到动态 Web Servlet 的通信

Question

你好，我正在尝试让一个在模拟器上运行的简单应用程序将数据发送到在同一台 PC 上运行的 servlet，使用 (http://10.0.2.2:8080/...) 作为 ip 连接到主机

补充阅读:这是一个 princable 测试，它有望让我在手机上运行一个应用程序并连接到家里运行的 servlet，最终将用于连接到 mysql 数据库。我有一些代码似乎可以做我想做的事，但我不确定它是否是固定的，或者我是否正确地实现了它

/** 安卓端 **/

import java.io.DataOutputStream; 
import java.io.OutputStream; 
import java.net.URL; 
import java.net.URLConnection; 

import android.app.Activity; 
import android.os.Bundle; 
import android.util.Log; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 
import android.widget.EditText; 
import android.widget.TextView;
import android.widget.Toast;

/**adapted code from online**/
public class Test extends Activity { 
     static final String TAG = "Test"; 
    // Called when the activity is first created.  

    protected static EditText username; 
    protected static EditText password;
    TextView tview;
    String uname ="";

    @Override 
    public void onCreate(Bundle icicle) { 
        super.onCreate(icicle); 
        setContentView(R.layout.testlogin); 

        username = (EditText)findViewById(R.id.username); 
        password = (EditText)findViewById(R.id.password);
        tview = (TextView)findViewById(R.id.view);
        Toast.makeText(this, "started",1).show();
        tview.append("\nstarted\n"); 
    } 

    public void login(View v) { //in testlogin.xml//android:onClick="login"
        Toast.makeText(this, "button pressed",1).show();
        Log.v(TAG, "button pressed");
        //tview.append("clicked\n");
        uname=username.getText().toString(); 
        networkthread ob = new networkthread(uname); 
    } 
}

class networkthread implements Runnable { 
        private static final String TAG = "Test"; 
        String uname; 
        public networkthread(String uname) { 
                this.uname =  uname; 
                Thread t = new Thread(this); 
                t.start(); 
        } 
        public void run(){


                Log.v(TAG, "inside sub thread"); 

                try { 
                    URL ob = new URL("http://10.0.2.2:8080/Server/test"); 
                    URLConnection           conn = ob.openConnection(); 
                    conn.setDoInput(true); 
                    conn.setDoOutput(true); 
                    OutputStream out = conn.getOutputStream(); 
                    DataOutputStream dos =  new DataOutputStream(out); 
                    dos.writeInt(uname.getBytes().length); 
                    dos.write(uname.getBytes(),0,uname.getBytes().length); 
                    dos.flush(); 
                    dos.close(); 
                    conn = null; 
                }catch(Exception e){ 
                        Log.v(TAG, "Exception:" +e); 
                        e.printStackTrace(); 
                } 
        } 
} 

/** 动态web项目中的Servlet端**/

import java.io.*; 
import java.net.*; 
import javax.servlet.*; 
import javax.servlet.http.*; 

public class test extends HttpServlet { 
    private InputStream is = null; 
    private OutputStream os = null; 
    private DataInputStream dis = null; 
    private DataOutputStream dos = null; 
    boolean isValid = false; 

    protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
        try{ 
            is = request.getInputStream(); 
            dis = new DataInputStream(is); 
            int  len = dis.readInt(); 
            byte data[] = new byte[len]; 
            dis.read(data,0,len); 
            String userName = new String(data); 
            System.out.println("username:" +userName); 
            is.close(); dis.close(); 
        } catch(Exception e){ 
            System.out.println(e); 
        } 
    } 

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
        processRequest(request, response); 
    } 


    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
        processRequest(request, response); 
    } 


    public String getServletInfo() { 
        return "Short description"; 
    } 

}

我对 android 和 servlet 都有一些经验当我运行它时没有错误，但是消息没有在 servlet 端恢复。我想我可能与应用程序不等待 servlet 的响应或 servlet 未在应用程序请求连接或类似内容的同时运行有关

是否有明显的原因导致它无法正常工作？我该如何解决这个问题，以便我可以继续使用手机上的测试应用程序连接到 servlet任何帮助将不胜感激，我希望在我解决问题之前积极参与这篇文章

Answer 1

应用

package com.test;

import java.io.BufferedReader;
import java.io.DataOutputStream; 
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream; 
import java.net.HttpURLConnection;
import java.net.URL; 
import java.net.URLConnection; 


import java.util.HashMap;
import java.util.logging.Logger;

import javax.net.ssl.HttpsURLConnection;

import org.apache.http.Header;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicHeader;
import org.apache.http.protocol.HTTP;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.app.Activity; 
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.os.AsyncTask;
import android.os.Bundle; 
import android.util.Log; 
import android.view.Menu;
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 
import android.widget.EditText; 
import android.widget.TextView;
import android.widget.Toast;


public class Test extends Activity { 
    static final String TAG = "Test"; 
    // Called when the activity is first created.  

    protected static EditText username; 
    protected static EditText password;
    TextView tview;
    String uname ="";
    JSONObject json;
    URL url;

    @Override 
    public void onCreate(Bundle icicle) { 
        super.onCreate(icicle); 
        setContentView(R.layout.testlogin); 

        username = (EditText)findViewById(R.id.username); 
        password = (EditText)findViewById(R.id.password);
        tview = (TextView)findViewById(R.id.view);
        Toast.makeText(this, "Started",1).show();
        Log.v(TAG,"\nStarted\n"); 
    } 

    public void login(View v) { //in testlogin.xml//android:onClick="login"
        Toast.makeText(this, "button pressed",1).show();
        Log.v(TAG, "button pressed");
        //tview.append("clicked\n");

        HashMap<String, String> hasmap=new HashMap<String, String>();
        hasmap.put("user",username.getText().toString());
        hasmap.put("pass",password.getText().toString());
        json = new JSONObject(hasmap);
        String sJSON = json.toString();
        new toServlet().execute(sJSON);//sends the jsonString to a aSync task
    }

    private class toServlet extends AsyncTask<String, Void, String> {
        @Override

        protected String doInBackground(String... urls) {

            // params comes from the execute() call: params[0] is the url.
            try {
                Log.v(TAG,"In background");
                return connection(urls[0]);//could send message to multible uls
            } catch (IOException e) {
                Log.v(TAG,"Error: "+e);
                return "Unable to retrieve web page. URL may be invalid.";
            }
        }
    }
    private String connection (String sJSON)throws IOException{//creates new connection each time
        Log.v(TAG, "Connection");
        Log.v(TAG,"In connection "+sJSON);
        URL url;
        InputStream is = null;
        HttpURLConnection conServlet;

        url = new URL("http://10.0.2.2:8080/CheckmateServerSuport/servlet?TAG="+sJSON);
        conServlet = (HttpURLConnection) url.openConnection();
        conServlet.setDoInput(true);
        //con.setDoInput(true);
        conServlet.setRequestMethod("POST");//can be get

        conServlet.connect();//makes the connection and send


        //Response
        is = conServlet.getInputStream();
        BufferedReader br = new BufferedReader(new InputStreamReader(is));
        Log.v(TAG,"Sent String ");

        String back = br.readLine();
        Log.v(TAG,""+back);

        return back;

    }
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }
}

小服务程序

package com.coreservlets;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.ObjectInputStream;
import java.io.PrintWriter;
import java.net.URLDecoder;
import java.util.HashMap;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.swing.text.AbstractDocument.BranchElement;

import org.json.JSONException;
import org.json.JSONObject;

@WebServlet("/servlet")
public class JSONServlet extends HttpServlet{

    public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {

        String user ="";
        String pass = "";

        System.out.println("In do Get");
        response.setContentType("application/json");

        try {
            JSONObject jsonRequest = new JSONObject(request.getParameter("TAG"));//from url in app
            System.out.println(jsonRequest);
            user = jsonRequest.getString("user");
            pass = jsonRequest.getString("pass");

            System.out.println("UserName: "+user+" Password: "+pass);

            //send back to app
            HashMap<String, String> map = new HashMap<String, String>();
            map.put("ok","ok");

            JSONObject replyJSON = new JSONObject(map);

            PrintWriter printW = response.getWriter();
            printW.println(replyJSON);

        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//essentioall dummy
        doGet(request, response);
    }
}