Browser extension sample – Chrome/Edge – HttpRequestViewer

Browser Extensions

The Evolution of Browser Extensions: From Web Customization to Advanced Development Tools – Part 2
We discussed about The evolution of the Browser extensions in the previous post. Lets quick learn how to create a Chrome/Edge/Firefox extension. I have mentioned “Advanced development tools” in the title, but never got chance to explore those capabilities earlier. We will create a simple extension to explore the power of it.

Creating a browser extension has never been easier, thanks to the comprehensive documentation and support provided by browser vendors. Below, we’ll walk through the steps to create a simple extension for both Chrome and Microsoft Edge using Manifest V3. We will use this tool to print the list of HTTP requests that are fired in a given browser and list it in the page.

Basics of extensions:

Manifests – A manifest is a JSON file that contains metadata about a browser extension, such as its name, version, permissions, and the files it uses. It serves as the blueprint for the extension, informing the browser about the extension’s capabilities and how it should be loaded.

Key Components of a Manifest File:

Here are the key components typically found in a Manifest V3 file:

1. Manifest Version: There are different versions of the manifest file, with Manifest V3 being the latest and most widely adopted version. Manifest V3 introduces several changes aimed at improving security, privacy, and performance with lot of controversies around it. Read more about the controversies at Ghostery.
2. Name and Version: These fields define the name and version of the extension. Choose a unique name and version. An excellent guide of version semantics is available here.
3. Description: A short description of the extension’s functionality.
4. Action: Defines the default popup and icon for the browser action (e.g., toolbar button).
5. Background: Specifies the background script that runs in the background and can handle events like network requests and alarms.
6. Content Scripts: Defines scripts and stylesheets to be injected into matching web pages.
7. Permissions: Lists the permissions the extension needs to operate, such as access to tabs, storage, and specific websites.
8. Icons: Specifies the icons for the extension in different sizes. For this post I created a simple icon using Microsoft Designer. I gave a simple prompt with the description above and I got the below image. Extension requires different sizes for showing it in different places. I used Chrome Extension Icon Generator and generated different sizes as needed.


9. Web Accessible Resources: Defines which resources can be accessed by web pages.

Create a project structure as follows:

|-- manifest.json
|-- popup.html
|-- popup.js
|-- background.js
|-- history.html
|-- history.js
|-- popup.css
|-- styles.css
|-- icons/
    |-- icon.png
    |-- icon16.png
    |-- icon32.png
    |-- icon48.png
    |-- icon128.png


  "name": "API Request Recorder",
  "description": "Extension to record all the HTTP request from a webpage.",
  "version": "0.0.1",
  "manifest_version": 3,
  "host_permissions": [""],
  "permissions": ["activeTab", "webRequest", "storage"],
  "action": {
    "default_popup": "popup.html",
    "default_icon": "icons/icon.png"
  "background": {
    "service_worker": "background.js"
  "icons": {
    "16": "icons/icon16.png",
    "32": "icons/icon32.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  "content_security_policy": {
    "extension_pages": "script-src 'self'; object-src 'self';"
  "web_accessible_resources": [{ "resources": ["images/*.png"], "matches": ["https://*/*"] }]

We have two options with the extension.

1. A button with record option to start recording all the HTTP requests
2. Link to view the history of HTTP Requests recorded

<!DOCTYPE html>
    <title>API Request Recorder</title>

    <link rel="stylesheet" href="popup.css" />
    <div class="heading">
      <img class="logo" src="icons/icon48.png" />
      <h1>API Request Recorder</h1>
    <button id="startStopRecord">Record</button>

    <div class="button-group">
      <a href="#" id="history">View Requests</a>

    <script src="popup.js"></script>

Two event listeners are registered for recording (with start / stop) and viewing history.
First event is used to send a message to the background.js, while the second one instructs chrome to open the history page in new tab.

document.getElementById("startStopRecord").addEventListener("click", () => {
  chrome.runtime.sendMessage({ action: "startStopRecord" });

document.getElementById("history").addEventListener("click", () => {
  chrome.tabs.create({ url: chrome.runtime.getURL("/history.html") });


<!DOCTYPE html>
    <link rel="stylesheet" href="styles.css" />
    <h1>History Page</h1>
      <tbody id="recorded-data-body">
        <!-- Data will be populated here -->
    <script src="history.js"></script>

Requests background.js to “getRecordedData” and renders the result in the html format.

document.addEventListener("DOMContentLoaded", () => {
  chrome.runtime.sendMessage({ action: "getRecordedData" }, (response) => {
    const tableBody = document.getElementById("recorded-data-body");
    response.forEach((record) => {
      const row = document.createElement("tr");
      const urlCell = document.createElement("td");
      const methodCell = document.createElement("td");
      const bodyCell = document.createElement("td");

      urlCell.textContent = record.url;
      methodCell.textContent = record.method;
      bodyCell.textContent = record.body;


Background JS works as a service worker for this extension, listening and handling events.
The background script does not have access to directly manipulate the user page content, but can post results back for the popup/history script to handle the cosmetic changes.

let isRecording = false;
let recordedDataList = [];

chrome.runtime.onMessage.addListener((message, sender, sendResponse) => {
  console.log("Obtined message: ", message);
  if (message.action === "startStopRecord") {
    if (isRecording) {
      isRecording = false;
      console.log("Recording stopped...");
      sendResponse({ recorder: { status: "stopped" } });
    } else {
      isRecording = true;
      console.log("Recording started...");
      sendResponse({ recorder: { status: "started" } });
  } else if (message.action === "getRecordedData") {
  } else {
    console.log("Unhandled action ...");

  (details) => {
    if (isRecording) {
      let requestBody = "";
      if (details.requestBody) {
        if (details.requestBody.formData) {
          requestBody = JSON.stringify(details.requestBody.formData);
        } else if (details.requestBody.raw) {
          requestBody = new TextDecoder().decode(new Uint8Array(details.requestBody.raw[0].bytes));
        url: details.url,
        method: details.method,
        body: requestBody,
      console.log("Recorded Request:", {
        url: details.url,
        method: details.method,
        body: requestBody,
  { urls: [""] },

Lets load the Extension

All set, now lets load the extension and test it.

  • Open Chrome/Edge and go to chrome://extensions/ or edge://extensions/ based on your browser.
  • Enable “Developer mode” using the toggle in the top right corner.
  • Click “Load unpacked” and select the directory of your extension.

Load extensionupload extension

  • Your extension should now be loaded, and you can interact with it using the popup.
  • When you click the “Record” button, it will start logging API requests to the console.

  • Click the “Record” button again and hit the “View requests” link in the popup to view the history of APIs.

I have a sample page ( with 4 API calls, which also loads images based on the API responses. You could see all the API requests that is fired from the page including the JS, CSS, Images and API calls.

Now its up to the developers imagination to build the extension to handle these APIs request and response data and give different experience.

Code is available in GitHub at HttpRequestViewer

The Evolution of Browser Extensions: From Web Customization to Advanced Development Tools

Browser Extensions

It’s been a while that I published a post. A week before, I created a new Chrome extension and shared with my team and noticed the new developers didn’t have knowledge on how powerful the browser extensions can be. It pushed me to write a short post about the history and power of browser extensions.

A Brief History

Browser extensions have dramatically transformed how users interact with the internet, offering a plethora of customization options and functionalities that enhance productivity, security, streamline workflows and user experience. These small software modules, integrated into web browsers like Chrome, Edge, Firefox etc., enable users and developers to tailor their browsing experience, automate tasks, and access additional features not available in standard browser installations. The evolution of browser extensions has marked a significant milestone in web development, fostering a community of developers who continuously innovate and simplify complex tasks.

The Early Days

Browser extensions trace their origins back to the early days of web browsers. The first notable implementation was by Internet Explorer in the late 1990s, which allowed for basic plugins to extend browser capabilities. Early days of these extensions allowed developers to add custom menu bars(also known as Browser Bands and Communication Bands), context menu options for seamless integration with extensions. CricInfo cricket score ticker was a popular toolbar that I have used in the early days. Internet download manager extension is one another toolbar which allowed the download of audios and videos, changed the life of lot of Dial-up connection users.

The Rise of Firefox

However, it was Mozilla Firefox that popularized the concept of extensions by providing a dedicated platform for the developers to create and submit the add-ons. Themes and skins are a fun part of extensions world. Greasemonkey,one of the early add-ons, allowed users to write custom code on top of extensions was a boon for customization. I used my first AdBlocker script from installed using Greasemonkey. This Add-on allowed me to create customize my own scripts without taking the hassle of publishing. Firefox’s various components like Add-ons, Extensions, and Plugins (Flash, Java, SilverLight, etc.) eventually evolved into standardized extensions.

The Chrome Era

Then came the days of Chrome. Google Chrome, introduced in 2008, revolutionized the extension landscape by offering streamlined APIs and a dedicated web store for its extensions. This facilitated easier development and distribution of extensions, leading to a surge in their popularity. The Chrome Web Store, launched in 2010, became a central hub for users to discover and install extensions, further solidifying their importance in the web ecosystem.

Extensions like Web Developer and React Developer Tools provide essential utilities for debugging, testing, and optimizing web applications. By leveraging browser APIs, developers can create tools that integrate seamlessly into their development environment, automating repetitive tasks and offering real-time insights into application performance.

Essential Extensions for Users

Some of the most used extensions include:
AdBlock / AdBlock Plus / uBlock Origin: Blocks ads on websites, improving load times and reducing clutter.
Microsoft Editor / Grammarly: Enhances writing by checking grammar, spelling, and style.
Honey: Automatically finds and applies coupon codes at checkout.
Bitwarden / LastPass: A password manager that stores and auto-fills passwords securely.
Momentum: Replaces the new tab page with a personal dashboard featuring a to-do list, weather, and inspirational quotes.
Dark Reader: Applies a dark theme to websites, reducing eye strain.

Must-Have Extensions for Developers

From a developer’s perspective, extensions are a boon. Some popular developer-friendly extensions are:
TamperMonkey – Modify website layouts, add/remove features, or automate actions – Alternative to Greasemonkey supporting userscripts.
React Developer Tools / Vue.js / – Provides debugging and inspection tools for React and Vue.js applications.
Redux DevTools – Allows developers to inspect every state and action payload for Redux applications.
Postman – A powerful tool for testing APIs by making HTTP requests.
JSON Viewer – Formats JSON data to make it more readable.
XPath Helper – Helps to find XPath expressions for elements on a webpage.
ColorZilla – Advanced color picker and gradient generator.
WhatFont – Identifies fonts used on a webpage.

We will see how to create a simple browser extension in the next post –Browser extension sample – Chrome/Edge – HttpRequestViewer

Installing OpenStack on AWS

1. Prerequisites – Minimal requirements for hosting in AWS, but not limited to:

  • Ubuntu Server 14.04.3 LTS – 64bit
  • Minimum 2VCPU – Cores
  • Minimum 8 GB RAM for just OpenStack (m4.large), Minimum 16 GB RAM for Sahara and clustering (m4.xlarge)
  • Atleast 40 GB of diskspace

2. Install Ubuntu if you dont have one

3. Verify installed version using

lsb_release -d
free -m
df -h

4. Update to the latest binaries

sudo apt-get update

5. Create a SUDO user – alternatively you can use the /devstack/tools/ to create a user after step 8

sudo -i
adduser stack			
	Enter new UNIX password:
	Retype new UNIX password:
	passwd: password updated successfully
	Changing the user information for username
	Enter the new value, or press ENTER for the default
	Full Name []:stack
	Room Number []:
	Work Phone []:
	Home Phone []:
	Other []:
	Is the information correct? [Y/n] Y

6. Add user to SUDOERs group

usermod -aG sudo stack 
echo "stack ALL=(ALL) NOPASSWD: ALL" >> /etc/sudoers

7. Switch to the new stack user

su - stack
check if the user can do sudo operations without password prompts
sudo ls -la /root

8. Switch to user home and install GIT and checkout devstack

cd ~
sudo apt-get install git
git clone

9. Configure devstack – update local.config and move to /devstack

cd /devstack
cp sample/local.conf .

* Update the passwords for the accounts


* If you are running on a physical machine with a static IP you can update the following property. On AWS its better to leave it commented as the local IP will be changed on each restart, unless the Elastic IP is assigned to the instance


* And add the following line at the end of the file. These entries will add the Sahara plugin (Data Processing) in OpenStack UI

echo "enable_plugin sahara git://" >> local.conf
echo "enable_plugin sahara-dashboard git://" >> local.conf
echo "enable_plugin ceilometer git://" >> local.conf

10. Start the stack services


* This takes up sometime and logs will be available at /opt/stack/logs. On successful completion you will find details something similar as below.

DevStack Component Timing
Total runtime         1169
run_process            57
test_with_retry         3
apt-get-update          3
pip_install           299
restart_apache_server  10
wait_for_service       11
git_timed             244
apt-get                69

This is your host IP address:
This is your host IPv6 address: ::1
Horizon is now available at
Keystone is serving at
The default users are: admin and demo
The password: St@ckNewPwd1

11. To access the dashboard hit in browser (with the ip as displayed in the above step). If you are running in local PC you can directly access with the above url. But if you are running on AWS, this is the internal IP and will not be available to the outside world. In this case, allow HTTP access on 80 port for the outside world and access the service with the Public IP or DNS hostname allocated to your instance. This in my case

Enable Registration in WordPress

In WordPress custom installations, the option for Registration of new users is disabled by default. To enable the registrations and allow logins for public you can follow the below steps.

Single site installation:

As soon as the installation is completed go to the WordPress Dashboard -> Settings

You will find an option Allow new registrations, you may need to select the Default Role for the newly registered members.


Multi-site/Network installation:

In case if you have installed WordPress in Multi site mode go to the Network Admin -> Settings and select the options under Allow new registrations section.


Once the registration is enabled it may be needed to add login options at places to find it easily. Follow these methods to do the same.

Method 1:

Add Meta widget in the sidebars or in footers. Select Appearance -> Widgets and select the Meta Widget.  Note that the menu will be available in Individual Site Dashboard, not in the Network Admin dashboard in case of Multi-site installation.



Method 2:

Add the login link in your Posts/Pages and it should be in the pattern, http(s)://HOSTNAME(:PORT)/(SUBDOMAINS)/wp-login.php.


  1. – MultiSite installation
  2. – SingleSite installation

Errors running builder ‘JavaScript Validator’ on project

I got this annoying exception on every auto build of my Dynamic Web Project.

“Errors occurred during the build.
Errors running builder ‘JavaScript Validator’ on project ‘GenieAlert’.

I was trying to stop the validation of Javascript in the Eclipse properties with the following options,

Windows -> Preferences -> Validation -> Client-side JavaScript Validator -> Checked Manual & Unchecked Build.

This option didn’t work out, then I realized that it happens only on the Build time. The following option came in handy to do that.

Project -> Properties -> Builders -> Unchecked ‘Javascript Validator’

Sometimes when you try to run the Web projects from eclipse on servers these JavaScript validation stops the deployment of the project on servers stating “JavaScript Validation Exception found”. I hope the above solutions will help in those situations too.

Famous Short URL services

URL shortening is a technique used to make the URLs substantially shorter in length and still direct to the required page. This is achieved by using an HTTP Redirect on a domain name that is very short in length, which links to the web page that has a long URL.

URL shortening is also used for beautify a link, track the url activity, in some cases to used to disguise the underlying address for legitimate purposes.

Some of the famous URL shortening services are follows:


Create Web Services using Axis Java2WSDL, WSDL2Java and Eclipse for all Servers manually – Part 2

With all the basic configurations done as specified in the last Article we continue to develop the Business logic.

  1. Create a class named, place four public methods add, subtract, multiply and delete and place the appropriate logics in it.
    public class Calculator {
    	public int add(int a, int b) {
    		return a+b  ;
    	public int subtract(int a, int b) {
    		return a-b ;
    	public int multiply(int a, int b) {
    		return a * b ;
    	public int divide(int a, int b) throws ArithmeticException {
    		return a /b ;
  2. This is the class that has to be exposed as the Web Service and we write the funky class to do all out operations like creating WSDL file, creating stub file etc.
  3. Generate WSDL file using Java2WSDL: Axis has a tool called Java2WSDL, which generates a WSDL file for a web service using a Java class. Java2WSDL file takes the following arguments.
    1. o – name for WSDL file -> calculator.wsdl
    2. n – target namespace ->
    3. l – url of web service -> http://<host:port>/<Project-Name>/services/calculator

    Summing up the above arguments the following command line arguments is created.

    String java2wsdlArgs[] = {"-ocalculator.wsdl", "", "-v", "-lhttp://localhost:8080/axis/services/calculator", ""} ;

    Read this Article on how to run the command line java tools from Eclipse.
    You can run the Java2WSDL as follows in the TestRunner class. Naah, don’t ask how, just put the following lines the main method and press CTRL + F11.

    try {
    	Java2WSDL.main(java2wsdlArgs) ;
    } catch (Exception e) {
    	e.printStackTrace() ;

    The Java2WSDL class has the System.exit(0); method called from inside. So lines after the Java2WSDL will not be executed. To get the other arguments supported you can just run Java2WSDL.main(new String[0]) ;. This will display all the arguments supported by Java2WSDL Utility and this works for other utilities also.
    After running this Utility you will find the calculator.wsdl file created in the root folder of the Project.

  4. Generate Server side and Client side codes using WSDL2Java: WSDL2Java is another tools provided by the AXIS, which can generate server side and client side Java classes using a WSDL file. These classes are needed for deploying the web service and also for accessing the web service using a Java client. This tool expects the following argument which includes the WSDL file generated in the last step.
    1. o – output folder -> src
    2. p – package for generated classes -> generated
    3. s – generate server side classes as well
    4. *.wsdl – WSDL file of any web service

    Summing up the above arguments the following command line arguments is created.

    String wsdl2javaArgs[] = {"-osrc", "-pcom.itechgenie.generated.service", "-s", "calculator.wsdl", "-v"} ;

    Read this Article on how to run the command line java tools from Eclipse.
    Now run the WSDL2Java utility as follows.

    try {
    	WSDL2Java.main(wsdl2javaArgs) ;
    } catch (Exception e) {
    	e.printStackTrace() ;

    Once the above command is run, Just refresh the project in eclipse, you will find the following files created inside the “com.itechgenie.generated.service” package.

    6. deploy.wsdd
    7. undeploy.wsdd

    The above files can be used in both Server and Clients side as Skeleton ( and the Stub ( respectively.

  5. Binding the business logic with the Skeleton: Take the Skeleton file and you will find the exact methods that were available in our Business logic class (
    Create a instance of the Business class and invoke the appropriate method from the skeleton as follows (Find the lines highlighted in yellow.).

    package com.itechgenie.generated.service;
    public class CalculatorSoapBindingImpl implements com.itechgenie.generated.service.Calculator{
    	Calculator calculatorImpl = new Calculator() ;
        public int add(int in0, int in1) throws java.rmi.RemoteException {
        	return calculatorImpl.add(in0, in1) ;
        public int subtract(int in0, int in1) throws java.rmi.RemoteException {
        	return calculatorImpl.subtract(in0, in1) ;
        public int divide(int in0, int in1) throws java.rmi.RemoteException {
        	return calculatorImpl.divide(in0, in1) ;
        public int multiply(int in0, int in1) throws java.rmi.RemoteException {
        	return calculatorImpl.multiply(in0, in1) ;

    That’s it; we are now done with the development part of the Web Service. All we have to do is to configure to make the service up and running.

  6. Last configurations to make our service available: Open the server-config.wsdd file inside the WEB-INF folder. You will find the following lines.
      <!--  Your Service from the deploy.wsdd file - Starts here -->
      <!--  Your Service from the deploy.wsdd file - Ends here -->

    Keep the file aside and open the deploy.wsdd from the WSDL2Java generated files. Copy the <service> … </service> tag completely and paste in between the comments said above.

  7. Conclusion: You can follow the steps 6 to 11 and create as many services as you want and paste them in the server-config.wsdd.
    With this the configurations for the Web Service is over. Export the Project as a War and deploy it in Web Server and point to the URL http://<host:port>/<Project-Name>/services
  8. This URL should display all the services generated from steps 6 to 11 with the links the WSDL files for the above.

    Click here to download the sample project.

Create Web Services using Axis Java2WSDL, WSDL2Java and Eclipse for all Servers manually – Part 1

There a lot of Web Service implementations available in market. The most widely used among them is the Axis way of implementation. There are a lot of Examples available in the web to create expose, consume the Web services using the Axis packages. But it is not feasible to work get the Axis complete packages inside corporate offices all of a sudden and yes I faced the same situation.

After some investment of time I found some funky stuff in web to create a Web Service with just a couple of jars in hand and off-course with the help of Eclipse.


  1. Eclipse, any version should be ok, but I was using the Eclipse Indigo with Ant installed in it.
  2. The set of jars needed. Jars are included in the Project sample.
    1. axis.jar
    2. commons-discovery-0.2.jar
    3. commons-logging.jar
    4. jaxrpc.jar
    5. log4j-1.2.15.jar
    6. saaj.jar
    7. wsdl4j.jar
    8. The sample web.xml, server-config.wsdd (These will be used later in the development steps).

Steps to develop Web Services:

  1. Create a Dynamic Web Project “SampleWebService” in Eclipse.
  2. Place the above said jars in the WEB-INF/jars folder.
  3. Open the Web.xml file and copy the following contents into it somewhere between tags. These contents are available in the sample attached.
        <display-name>Apache-Axis Servlet</display-name>
        <display-name>Axis Admin Servlet</display-name>
  4. Copy the server-config.wsdd next to web.xml file. We will reuse this file once again after complete the business logic of the server.
  5. Now the basic configurations are complete, we have to develop the business logic for the Web Service. In my example I have taken the Old school Calculator sample.
    Click here to go to the next Part of this article.

Simple methods to Create, Read and Delete Cookies using JavaScript


1. createCookie(name,value,days) – Void function.

name – Name for the cookie to be created
value – Value of the cookie
days(INT – Non Madatory) – Number of days to keep the cookie in browser. If not specified the cookie will expire as soon as soon the browser is closed.

2. readCookie(name) – Returns the value of the cookie.

name – Name given at the time of creation

3. eraseCookie(name) – Void function.

Dependency – createCookie method should be in place.

function createCookie(name,value,days) {
if (days) {
var date = new Date();
var expires = "; expires="+date.toGMTString();
else var expires = "";
document.cookie = name+"="+value+expires+"; path=/";
function readCookie(name) {
var nameEQ = name + "=";
var ca = document.cookie.split(';');
for(var i=0;i &lt; ca.length;i++) {
var c = ca[i];
while (c.charAt(0)==' ') c = c.substring(1,c.length);
if (c.indexOf(nameEQ) == 0)
return c.substring(nameEQ.length,c.length);
return null;
function eraseCookie(name) {

Printing Complex Layouts in Adobe Flex – FlexPrintJob

I have come across a basic need for printing a complex layout in the Adobe Flex. After a long search i thought the following will be helpful to all if shared.


1. My layout has the following. Header (Fixed, to be shown in all page.), First Page Header (Displayed only in single page), DataGrid with data rolling out to more than one page, Fixed footer following the DataGrid and a Footer that come only in last page of the Printed output.
2. I am given only the outer most component object and list of all ids of the following components.
3. No server side support is available.


1. My DataGrid is not accessible directly.
2. Complex layout and needed Paginationrn3. Fixed, floating header and footers.


With reference to the Adobe Live docs, the solutions is almost near except to the complex structure.
rnI have created a Template that holds all the data to be iterated in the report. I contains the sections like Fixed Header, Floating Header, DataGrid, Fixed Footer, Floating Footer as follows.

1. PrintTemplate.mxml

<s:VGroup id="allPageHeader" width="100%" />
< s:VGroup id="firstPageHeader" width="100%" />
< mx:PrintDataGrid id="printDataGrid" width="100%" />
< s:VGroup id="allPageFooter" width="100%" />
< s:VGroup id="lastPagefooter" width="100%" />

2. PrintSample.mxml

protected function doPrint(outerGroup:DisplayObjectContainer, fixedHeaderIDs:ArrayCollection, floatHeaderIDs:ArrayCollection, dataGridId:String, floatFooterIDs:ArrayCollection , fixedFooterIDs:ArrayCollection):void{...}

Here we have to pass the list of IDs of the sections as we need to the doPrint method as follows.

doPrint(outerGroup, fixedHeaderIDs, floatHeaderIDs, dataGridId, fixedFooterIDs, floatFooterIDs);Completing the rendering the print object will be sent to printer and a popup will be shown.

Source Code: Printing in Adobe Flex


In the above example, if the Printout is taken with the printAsBitmap set to false, then there will be thick line under the header of the DataGrid ie, the PrintDataGrid. To solve this problem you have to use a Header Renderer and set a background color or Image for the header as follows.

<?xml version="1.0" encoding="utf-8"?>
< s:SparkSkin xmlns:fx="http:/" xmlns:s="library:/" xmlns:mx="library:/" > < s:Rect left="0" right="0" top="0"> < s:fill> < s:BitmapFill source="@Embed(''header.png'')"/> 
< /s:fill> < s:stroke> < s:SolidColorStroke color="grey" /> 
< /s:stroke> < /s:Rect>< /s:SparkSkin>

Save the file as SampleSkin and add this skin to the headerBackroundSkin property of PrintDataGrid in the PrintTemplate as follows.

<mx:PrintDataGrid id="printDataGrid" width="100%" headerBackgroundSkin="SampleSkin" />

This will resolve the issue and set a neat header to the DataGrid in the print.