New Country, New Job!

I got to know about a job in Malaysia in the month of March while I was working at Virtusa. At that point I didn't know in which company I would be working in, but I wanted to work in a foreign country so applied. Days later I got a call from an agent in Sri Lanka that some people would be coming down from Malaysia for the interview and I would be called within 2 weeks time. To be honest I wasn't sure of what he said but kept my fingers crossed.

Right after two weeks I did get a call from the agent saying I have an interview on 4th of April at Galadari Hotel Colombo. I went there and there were three people from Malaysia from the company MIMOS including the CTO.

MIMOS is Malaysia's National Research and Development Institute for ICT. It comes directly under the purview of MOSTI, Ministry of Science, Technology and Innovation. It seemed a really good offer for me and I did quite well in the interview due to my preparedness. The CTO was impressed of my little Arduino Projects and during the interview I knew that I had at least 70% chance of getting in.

After two more weeks I got the news that I have been selected out of 14 interviewees as one of the potential employees. I was over the moon and started preparing to come to Malaysia. After more than one month of preparing I finally landed in Malaysia on 02nd of June 2013 at 7:15 a.m.

Now I am temporarily residing at Bukit Jalil which is closed to Technology Park Malaysia which is where MIMOS is located.

All thanks to god for giving me such a wonderful opportunity. 

RC Car Tear Down and Control Using Arduino

In a previous post I showed the RC Car I bought and the internals of it. As I mentioned, there was a RX 2 Chip inside the Car but the pin layout was not exactly same as it is mentioned in the datasheet. So I had to ask my wife for help in controlling the car from the remote control and used a multimeter to find out which pins are being activated for each command. The datasheet mentioned that;

1. Pin No 11 = Forward
2. Pin No 12 = Backward
3. Pin No 6 = Right
4. Pin No 7 = Left

But as it turns out 

Pin No 6 is Left and Pin No 7 is Right. So after finding those out I soldered required wires to the Circuit and hoping to work more on that. 

The video of the testing is below

Best Practice in Web Services Usage

Web Services are everywhere and so widely used today. There are several types of Web Services but most widely used ones are SOAP based, REST based web services. I am not going to defferentiate the two here but SOAP based Web Services are much more widely used than REST based mainly because of their reliability and security.

I am not going to implement a fully fledged web service here but just to provide some additional security measures that can be implemented to secure your web services. Nope this not about Authentication and Authorization. Those needs to be implemented anyhow.

According to the famous US based Internet Application security vulnerability testing company Veracode, web services must only expose their WSDL, XSD only to their intended and authorized consumers. This enables the information web services expose to be really limited to people who are intended to use those. But by default web services allow to see the WSDL and XSD by calling the below url.

http://<host>:<port>/MyApplication/services/MyService?wsdl

or

http://<host>:<port>/MyApplication/services/MyService?xsd

This can be restricted by writing a Servlet Filter similar to the below one which Expects Query Strings to be Base64 Encoded and have the format like below

ServiceDefinition#1234567890

1234567890 can be replaced with a timestamp in milli seconds so that the Encoded string will be different each time.

When encoded it will look like the following

U2VydmljZURlZmluaXRpb24jMTIzNDU2Nzg5MA==

The implementation of the Filter is as follows

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.util.HashMap;
import java.util.Map;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.axiom.om.util.Base64;
import org.apache.commons.io.FilenameUtils;

public class InvalidUrlFilter implements Filter {
    
    private Map<String, byte[]> wsdlMap = new HashMap<String, byte[]>();    
    
    private Map<String, byte[]> secureWsdlMap = new HashMap<String, byte[]>();

    @Override
    public void destroy() {
        wsdlMap.clear();
        wsdlMap = null;
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain filterChain) throws IOException, ServletException {
        doFilter((HttpServletRequest) request, (HttpServletResponse) response, filterChain);        
    }
    
    public void doFilter(HttpServletRequest request, HttpServletResponse response,
            FilterChain filterChain) throws IOException, ServletException {
        String queryString = request.getQueryString();
        boolean isError = false;
        boolean isWsdlProcessed = false;
        if(queryString != null) {
            queryString = queryString.toUpperCase();            
            if(queryString.endsWith("WSDL") || queryString.endsWith("XSD")) {
                response.sendError(HttpServletResponse.SC_NOT_FOUND);
                return;
            }
            if(isValidWSDLRequest(request.getQueryString())) {
                String serviceName = FilenameUtils.getBaseName(request.getRequestURI().toString());
                
                byte[] wsdlbytes = secureWsdlMap.get(serviceName);
                if(wsdlbytes == null) {
                    wsdlbytes = wsdlMap.get(serviceName);
                    if(request.isSecure()) {                    
                        String wsdl = new String(wsdlbytes, "UTF-8");
                        wsdl = wsdl.replaceAll("location=\"http\"", "location=\"https\"");
                        wsdlbytes = wsdl.getBytes();
                        secureWsdlMap.put(serviceName, wsdlbytes);
                    } 
                }        
                
                try {                
                    response.setContentType("text/xml");            
                    response.getOutputStream().write(wsdlbytes);
                    isWsdlProcessed = true;
                } catch(Exception e) {
                    isError = true;
                } finally {
                    if(!isError && isWsdlProcessed) {
                        response.getOutputStream().flush();
                        response.getOutputStream().close();
                    }
                }
            } 
        }
        
        if(!isWsdlProcessed) {
            filterChain.doFilter(request, response);
        }
                
    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        ServletContext servletContext = filterConfig.getServletContext();
        File servicesDir = new File(servletContext.getRealPath("/WEB-INF/services"));
        
        loadWsdl(servicesDir);
        
    }
    
    private String decoder(String value) {
        String result = "";
        try {
            if(value != null && !value.equals("")) {
                String tmpResult = new String(new Base64().decode(value), "UTF-8");
                
                String[] vals = tmpResult.split("#");
                if(vals.length > 1) {
                    result = vals[0];
                }                
            } 
        } catch (UnsupportedEncodingException e) {
            // Must be Logged
        }
        return result;
    }
    
    private void loadWsdl(File servicesDir) {
        for(File directory:servicesDir.listFiles()) {
            if(directory.isDirectory()) {
                String serviceName = FilenameUtils.getBaseName(directory.getName());
                InputStream is = null;
                ByteArrayOutputStream os = null;
                try {
                    is = new FileInputStream(directory.getAbsolutePath()+"/META-INF/"+serviceName+".wsdl");
                    os = new ByteArrayOutputStream();
                    
                    byte[] data = new byte[1024];
                    int read = 0;
                    while((read = is.read(data)) > 0) {
                        os.write(data, 0, read);
                    }
                    os.flush();                
                    
                    wsdlMap.put(serviceName, os.toByteArray());
                    
                } catch (Exception e) {
                    // Must log                    
                } finally {
                    if(os != null) {
                        try {
                            os.close();
                        } catch (IOException e) {
                            
                        }
                    }
                    
                    if(is != null) {
                        try {
                            is.close();
                        } catch(IOException e) {
                            
                        }
                    }
                }
                
            }
        }
    }
    
    private boolean isValidWSDLRequest(String queryString) {
        boolean result = false;
        String[] values = queryString.split("&");
        for(String value:values) {
            if(decoder(value).equals("ServiceDefinition")) {
                result = true;
                break;
            }
        }
        return result;
    }
    
    
    
    
}

And web.xml will have the following

    <filter>
        <filter-name>InvalidUrlFilter</filter-name>
        <filter-class>com.shazin.filters.InvalidUrlFilter</filter-class>
    </filter>
    
    <filter-mapping>
        <filter-name>InvalidUrlFilter</filter-name>
        <servlet-name>AxisServlet</servlet-name>
    </filter-mapping>

Now the WSDL can be accessed by using a URL similar to

http://<host>:<port>/MyApplication/services/MyService?U2VydmljZURlZmluaXRpb24jMTIzNDU2Nzg5MA==

Restricts the exposure of the Web Service WSDL to intended consumers only. But for this to work the web services must use HTTPS. If not just Base64 encoding wouldn't suffice. Then it needs to be encrypted before Base64 encoded.

My New RC Car

This may sound really childish but yes I bought myself a Brand New Ferrari Model RC Car. It is a Red color car which you can see in the below image.

The RC Car uses Radio Frequency 27 Mhz to receive control from the Remote. This is how the under the hood of the car looks like.

Some more closer looks

The IC in RC Car is RX - 2 which is the common IC in Chinese RC Cars.

The under the hood of the Remote Control looks like this.

The IC of the Remote Control is TX - 2. This is the datasheet for TX - 2 and RX - 2 

Android 4.1.2 Jelly Bean and Arduino Mega 2560 with USB Host Shield Communication

Few  weeks ago I wrote my first Android Jelly Bean App named ColorChanger. Since then I wanted to integrate it with Arduino and Control a physical RGB LED Light from the ColorChanger Android App. I finally managed to get it done using the following Items.

1. Arduino Mega 2560 Rev 3
2. DFRobot USB Host Shield 
3. Arduino IDE 0023
4. ADK Library
5. 1 RGB LED
6. 1 1k Resistor
7. Few Jumper Cables
8. One USB to Micro USB Cable

Few things changed from the original ColorChanger App starting from the AndroidManifest.xml where I had to allow my MainActivity to listen for USB_ACCESSORY_ATTACHED intent action and when my Accessory connects open the ColorChanger App.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.shazin.colorchanger"
    android:versionCode="1"
    android:versionName="1.0" >
    
    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="17" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.shazin.colorchanger.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <action android:name="android.hardware.usb.action.USB_ACCESSORY_ATTACHED" />
                
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
            
            <meta-data android:name="android.hardware.usb.action.USB_ACCESSORY_ATTACHED"
                android:resource="@xml/accessory_filter" /> 
        </activity>
    </application>

</manifest>

The filtering criteria is placed in res/xml/accessory_filter.xml file which is as follows

<?xml version="1.0" encoding="utf-8"?>

<resources>
    <usb-accessory model="ColorChangerApp" manufacturer="Shazin Sadakath" version="1.0"/>
</resources>

Then my MainActivity class changed as follows

package com.shazin.colorchanger;

import java.io.FileDescriptor;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.graphics.Color;
import android.hardware.usb.UsbAccessory;
import android.hardware.usb.UsbManager;
import android.os.Bundle;
import android.os.ParcelFileDescriptor;
import android.view.Menu;
import android.widget.LinearLayout;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;
import android.widget.TextView;
import android.widget.Toast;


public class MainActivity extends Activity implements OnSeekBarChangeListener, Runnable {

    private TextView textViewColor;
    
    private SeekBar seekBarRed;
    
    private SeekBar seekBarGreen;
    
    private SeekBar seekBarBlue;
    
    private byte red, green, blue;
    
    private LinearLayout linearLayout;
    
    private UsbAccessory mAccessory;
    
    private ParcelFileDescriptor mFileDescriptor;
    
    private FileInputStream mInputStream;
    
    private FileOutputStream mOutputStream;
    
    private UsbManager mUsbManager;
    
    private static final String ACTION_USB_PERMISSION = "com.android.example.USB_PERMISSION";
        private final BroadcastReceiver mUsbReceiver = new BroadcastReceiver() {
         
            public void onReceive(Context context, Intent intent) {
                String action = intent.getAction();
                if (ACTION_USB_PERMISSION.equals(action)) {
                    synchronized (this) {
                        UsbAccessory accessory = (UsbAccessory) intent.getParcelableExtra(UsbManager.EXTRA_ACCESSORY);

                        if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)) {
                            if(accessory != null){
                                //call method to set up accessory communication
                                openAccessory();
                            }
                        }
                        else {
                            //Log.d(TAG, "permission denied for accessory " + accessory);
                            Toast.makeText(context, "permission denied for accessory "+accessory, 2).show();
                        }
                    }
                    unregisterReceiver(mUsbReceiver);
                }    
                
            }
        };
    
        public final BroadcastReceiver mUsbDetachReciever = new BroadcastReceiver() {

            @Override
            public void onReceive(Context context, Intent intent) {
                String action = intent.getAction();
                if (UsbManager.ACTION_USB_ACCESSORY_DETACHED.equals(action)) {
                    UsbAccessory accessory = (UsbAccessory)intent.getParcelableExtra(UsbManager.EXTRA_ACCESSORY);
                    if (accessory != null) {
                        cleanUp();                
                    }
                    unregisterReceiver(mUsbDetachReciever);
                }
                
            }
            
        };
        


        private boolean mPermissionRequestPending;        
        
        private void cleanUp() {
            try {
                if(mFileDescriptor != null)
                    mFileDescriptor.close();
                
                if(mInputStream != null) 
                    mInputStream.close();
                
                if(mOutputStream != null)
                    mOutputStream.close();
                mAccessory = null;
                mUsbManager = null;
                Toast.makeText(this, "Closed all resources", 2).show();
            } catch (IOException e) {
                Toast.makeText(this, "Error occured "+e, 2).show();
            }
        }
        
            
    @SuppressLint("NewApi")
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        linearLayout = (LinearLayout) findViewById(R.id.linearLayout);
        
        textViewColor = (TextView) findViewById(R.id.textViewColor);
                
        seekBarRed = (SeekBar) findViewById(R.id.seekBarRed);
        seekBarGreen = (SeekBar) findViewById(R.id.seekBarGreen);
        seekBarBlue = (SeekBar) findViewById(R.id.seekBarBlue);
        
        seekBarBlue.setOnSeekBarChangeListener(this);
        seekBarGreen.setOnSeekBarChangeListener(this);
        seekBarRed.setOnSeekBarChangeListener(this);
        
        textViewColor.setText(String.format("(%d, %d, %d)", red, green, blue));
        linearLayout.setBackgroundColor(Color.rgb(red, green, blue));
        
        
        mAccessory = (UsbAccessory) getIntent().getParcelableExtra(UsbManager.EXTRA_ACCESSORY);
        Toast.makeText(this, "USB Accessory = "+mAccessory, 2).show();
        
        mUsbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
        Toast.makeText(this, "USB Manager = "+mUsbManager, 2).show();
        
        PendingIntent mPermissionIntent = PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), 0);
        IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
        registerReceiver(mUsbReceiver, filter);
        Toast.makeText(this, "Intent Registered", 2).show();
        
        if(mUsbManager.hasPermission(mAccessory)) {
            Toast.makeText(this, "Accessory has permission", 2).show();
            unregisterReceiver(mUsbReceiver);
            openAccessory();
        } else {            
            Toast.makeText(this, "Accessory has no permission", 2).show();
            synchronized (mUsbReceiver) {                
                if (!mPermissionRequestPending) {
                    mUsbManager.requestPermission(mAccessory, mPermissionIntent);
                    Toast.makeText(this, "Permission Request Sent", 2).show();
                    mPermissionRequestPending = true;
                }
            }
        }
        
        IntentFilter filter2 = new IntentFilter(ACTION_USB_PERMISSION);
        filter2.addAction(UsbManager.ACTION_USB_ACCESSORY_DETACHED);
        registerReceiver(mUsbDetachReciever, filter2);        
        
    }
    
    public void onDestroy() {
        super.onDestroy();
        cleanUp();
    }
    
    @SuppressLint("NewApi")
    private void openAccessory() {
        //Log.d(TAG, "openAccessory: " + accessory);
        mFileDescriptor = mUsbManager.openAccessory(mAccessory);
        Toast.makeText(this, "Accessory Opened", 2).show();
        if (mFileDescriptor != null) {
            FileDescriptor fd = mFileDescriptor.getFileDescriptor();
            Toast.makeText(this, "File Desc "+fd, 2).show();
            mInputStream = new FileInputStream(fd);
            mOutputStream = new FileOutputStream(fd);
            
        }
    }

    @Override
    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;
    }

    @Override
    public void onProgressChanged(SeekBar seekBar, int value, boolean flag) {
        if(seekBar == seekBarRed) {
            red = (byte) value;
        } else if(seekBar == seekBarGreen) {
            green = (byte) value;
        } else if(seekBar == seekBarBlue) {
            blue = (byte) value;
        }
        linearLayout.setBackgroundColor(Color.rgb(red & 0xFF, green & 0xFF, blue & 0xFF));
        textViewColor.setText(String.format("(%d, %d, %d)", red & 0xFF, green & 0xFF, blue & 0xFF));
        if(mOutputStream != null) {
            try {
                byte[] data = new byte[4];
                data[0] = 0x2;
                data[1] = red;
                data[2] = green;
                data[3] = blue;
                mOutputStream.write(data);
                mOutputStream.flush();
            } catch (IOException e) {
                Toast.makeText(this, "Error "+e, 2).show();
            }
        }    
    }

    @Override
    public void onStartTrackingTouch(SeekBar arg0) {
        // TODO Auto-generated method stub
        
    }

    @Override
    public void onStopTrackingTouch(SeekBar arg0) {
        // TODO Auto-generated method stub
        
    }

    @Override
    public void run() {
    
    }

}

And the Arduino Sketch is as follows

#include <avrpins.h>
#include <max3421e.h>
#include <usbhost.h>
#include <usb_ch9.h>
#include <Usb.h>
#include <usbhub.h>
#include <avr/pgmspace.h>
#include <address.h>

#include <adk.h>

#include <printhex.h>
#include <message.h>
#include <hexdump.h>
#include <parsetools.h>

// For Arduino IDE 1.0.x Only following two is needed

#include <adk.h>
#include &ltusbhub.h>

USB Usb;
USBHub hub0(&Usb);
USBHub hub1(&Usb);
ADK adk(&Usb,"Shazin Sadakath",
            "ColorChangerApp", // This name Should match with xml/res/accessory_filter.xml name
            "Color Changer App",
            "1.0",
            "http://shazsterblog.blogspot.com",
            "0000000012345678");

#define  LED1_RED       5
#define  LED1_GREEN       4
#define  LED1_BLUE       3

void setup();
void loop();

void init_leds()
{
    digitalWrite(LED1_RED, 0);
    digitalWrite(LED1_GREEN, 0);
    digitalWrite(LED1_BLUE, 0);

    pinMode(LED1_RED, OUTPUT);
    pinMode(LED1_GREEN, OUTPUT);
    pinMode(LED1_BLUE, OUTPUT);
}

void setup()
{
    Serial.begin(115200);
    Serial.println("\r\nADK demo start");
        
        if (Usb.Init() == -1) {
          Serial.println("OSCOKIRQ failed to assert");
        while(1); //halt
        }//if (Usb.Init() == -1...


    init_leds();
}

void loop()
{
  uint8_t rcode;
  uint8_t msg[4] = { 0x00 };
   Usb.Task();
   
   if( adk.isReady() == false ) {
     analogWrite(LED1_RED, 255);
     return;
   }
   uint16_t len = sizeof(msg);
   
   rcode = adk.RcvData(&len, msg);
   if( rcode ) {
     USBTRACE2("Data rcv. :", rcode );
   } 
   if(len > 0) {
     if(msg[0] == 0x2) {
         USBTRACE("\r\nData Packet.");
         uint8_t r = (msg[1]) & 0xFF;
         uint8_t g = (msg[2]) & 0xFF;
         uint8_t b = (msg[3]) & 0xFF;
         analogWrite(LED1_RED, 255 - r);
         analogWrite(LED1_GREEN, 255 - g);
         analogWrite(LED1_BLUE, 255 - b);
     }
     

   }
   
   msg[0] = 0x1;
   
      delay( 10 );       
}

The video of the whole thing working together is available below.

 

References 

• http://www.circuitsathome.com/mcu/google-open-accessory-interface-for-usb-host-shield-library-2-0-released
• http://developer.android.com/tools/adk/adk2.html
• https://docs.google.com/file/d/0B9L9ONCpLAwGbU5Hd0pIVUlmMTQ/edit?usp=sharing

How to use jqgrid with Struts2 JSON result

jqgrid plugin is one of the most famous jquery plugins to display tables in web pages which enables searching, sorting and filtering etc.

I wanted to integrate jqgrid with Struts2 but there was little to no proper documentation on how to do it. I wanted to use JSON format and no website has clearly mentioned (or atleast I didn't find any) the format of the JSON and how it needs to be created using Struts2. So after some trial and error I managed to get this to work.



struts.xml will look like the following

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
"http://struts.apache.org/dtds/struts-2.0.dtd">
 
<struts>    

     <constant name="struts.devMode" value="true" />     
    <package name="user" namespace="/User" extends="struts-default">
        <result-types>
            <result-type name="json" class="com.googlecode.jsonplugin.JSONResult"/>
        </result-types>    
        <action name="getUsersList" class="com.shazin.struts2hello.action.GetUsersListAction">
               <result type="json" />
          </action>        
          <action name="ListUsers" class="com.shazin.struts2hello.action.ListUsersAction">
            <result name="SUCCESS">../pages/list_users.jsp</result>            
        </action>
    <package>

There are two Actions getUserList which will return the JSON result and ListUsers which will render the JSON into the jqgrid. Following is the source code for GetUsersListAction and since this object is directly used to serialize the result into JSON it needs to have the instance variable names as it is with getters and setters.

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

import com.opensymphony.xwork2.Action;
import com.shazin.struts2hello.model.User;
import com.shazin.struts2hello.service.UserService;
import com.shazin.struts2hello.service.impl.UserServiceImpl;

public class GetUsersListAction {
    
    private String page;  
    private Double total;  
    private String records;  
    private List rows; 
    
    public String execute() {
        page = "1";
        total = 1.0;        
        UserService userService = new UserServiceImpl(); 
        List<User> usersList = userService.getAllUsers(); // Retrieves users from database
        records = usersList.size()+"";
        rows = new ArrayList();
        int id = 1;
        for(User u:usersList) {
            rows.add(new Row(String.valueOf(id), 
                    new String[] { String.valueOf(id), u.getFirstName() , u.getLastName(), u.getUsername(), u.getEmail() }));
            id++;
        }
        
        return Action.SUCCESS;
    }

    public String getPage() {
        return page;
    }

    public void setPage(String page) {
        this.page = page;
    }

    public Double getTotal() {
        return total;
    }

    public void setTotal(Double total) {
        this.total = total;
    }

    public String getRecords() {
        return records;
    }

    public void setRecords(String records) {
        this.records = records;
    }

    public List getRows() {
        return rows;
    }

    public void setRows(List rows) {
        this.rows = rows;
    }

    public class Row implements Serializable {
        private String id;
        
        private String[] cell;
        
        public Row() {
            
        }
        
        public Row(String id, String[] cell) {
            setId(id);
            setCell(cell);
        }

        public String getId() {
            return id;
        }

        public void setId(String id) {
            this.id = id;
        }

        public String[] getCell() {
            return cell;
        }

        public void setCell(String[] cell) {
            this.cell = cell;
        }        
        
    }    
}

The JSON output will be like this and it should be in this format to work with jqgrid.

{"page":"1","records":"1","rows":[{"cell":["1","Shazin","Sadakath","ssadakath","shazin.sadakath@gmail.com"],"id":"1"}],"total":1.0}

ListUsers action source code is really simple

public class ListUsersAction {
    public String execute() {
        return "SUCCESS";
    }
}

Finally the source code for list_users.jsp page

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<link rel="stylesheet" type="text/css" media="screen" href="../css/jquery-ui-1.10.2.custom.css" />
<link rel="stylesheet" type="text/css" media="screen" href="../css/ui.jqgrid.css" />
<script src="../js/jquery-1.7.2.min.js" type="text/javascript"></script>
<script src="../js/jquery-ui-1.10.2.custom.min.js" type="text/javascript"></script>
<script src="../js/i18n/grid.locale-en.js" type="text/javascript"></script>
<script src="../js/jquery.jqGrid.min.js" type="text/javascript"></script>
<title>List Users</title>
<script type="text/javascript"> 
jQuery().ready(function (){
    //alert('Hi');
    jQuery("#list1").jqGrid({
           url:'/Struts2Hello/User/getUsersList.action',
        datatype: "json",
           colNames:['User Id','First Name', 'Last Name', 'Username','Email'],
           colModel:[
               {name:'id',index:'id', width:75},
               {name:'firstName',index:'firstName', width:90},
               {name:'lastName',index:'lastName', width:100},
               {name:'username',index:'username', width:80},
               {name:'email',index:'username', width:80}                   
           ],
           rowNum:10,
           autowidth: true,
           rowList:[10,20,30],
           pager: jQuery('#pager1'),
           sortname: 'id',
        viewrecords: true,
        sortorder: "desc",
        caption:"Users"
    }).navGrid('#pager1',{edit:false,add:false,del:false});    
});                
</script>
</head>
<body>
    <table id="list1"></table>
    <div id="pager1"></div>
</body>
</html>

Fixing "name" is not translated in locales in Android

If you develop Android applications which has multiple locales, you might face an error similar to the below one

"<Value Name>" is not translated in <Locales> ...

This is because some names which you don't want to be translated are also taken as translatable names. The easiest fix for this is to mark the error cause name tag as

<string name="myname" translatable="false">

<string-array name="myname" translatable="false">

in string, string-array element. Or you can define all your non-translatable strings in a resource file called donottranslate.xml. Or, you can ignore the issue with a tools:ignore="MissingTranslation" attribute.