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Gmail Contextual Gadgets with GWT

Today we’ll create Gmail Contextual gadget with the help of GWT.
According to Google definition, Contextual gadget is “a gadget that is triggered by clues in Gmail, such as the contents of Subject lines and email messages. For example, Gmail already provides a YouTube contextual gadget. If the body of an email contains a link to a YouTube video, a clickable thumbnail view of the video appears at the bottom of the email.”

Gmail Contextual gadgets can work only with Google Apps for domain, you can’t set it up with your * account, because gadgets are available via Google Apps Marketplace only.

There are very good specs from Google about creating gadgets with pure JavaScript I recommend to look through it, to understand, what we are doing.
GWT version has some differences with native JavaScript, we will take look at this.


<?xml version="1.0" encoding="UTF-8" ?>
<ApplicationManifest xmlns="">
    <!-- URL explaining how customers get support. -->
        <Link rel="support" href="" />
    <!-- URL that is displayed to admins during the deletion process,
     to specify policies such as data retention, how to claim accounts, etc. -->
        <Link rel="deletion-policy" href="" />

    <!-- Name and description pulled from message bundles -->
    <Name>Demo Contextual Gadget</Name>
    <Description>Simple GWT gadget</Description>

    <!-- EXTRACTOR -->
    <Extension id="body" type="contextExtractor">
        <Name>Email Body</Name>
        <Param name="email_body" value=".*" />
        <Triggers ref="CtxDemoGadget" />
        <Scope ref="bodyScope" />
        <Container name="mail" />

    <!-- GADGET -->
    <Extension id="CtxDemoGadget" type="gadget">
        <Name>Demo Gmail Contextual Gadget</Name>
        <!-- Public path to your main class -->
        <Container name="mail" />

    <!-- SCOPE -->
    <Scope id="bodyScope">

I take only Body Extractor, you can add any other.
Now, we need to define extractors for GWT application, create Extractors.xml in the same folder, where placed your main class with following lines:

<?xml version="1.0" encoding="UTF-8"?>
<Require feature="google.contentmatch">
   <Param name="extractors">

To add multiply extractors use:

<Param name="extractors">,,

GWT application code

package com.mozgoweb.demo.client;


 * Main entry point.
 * @author Denis Lunev <>
 * Twitter functionality based on "Cross-Site Scripting with GWT and Twitter"
 * by Alex Moffat
@ModulePrefs(title = "DemoGadget", author = "Denis Lunev", author_email = "")
@GadgetFeature.FeatureName(value = "google.contentmatch")
@InjectModulePrefs(files = {"Extractors.xml"})

public class CtxGadgetEntryPoint extends Gadget<UserPreferences> {
    public CtxGadgetEntryPoint() {}

     For gadget use init() instead of onModuleLoad 
    protected void init(UserPreferences preferences) {
        final JsArray<JavaScriptObject> matches = jsGetContentMatches();
        if (matches != null) {
            final int numMatches = matches.length();
            result = new JSONObject[numMatches];
            for (int i = 0; i < numMatches; i++) {
                //Do something with email body
	Native JS method to invoke extractors
    native JsArray<JavaScriptObject> jsGetContentMatches() /*-{
        return google.contentmatch.getContentMatches();

Then build the project and open xml file with main class, in my case it’s build/web/com.mozgoweb.demo.gadget/CtxGadgetEntryPoint.gadget.xml
Make sure, that your extractors are presented and add view=”card” to Content tag:

...<Content type="html" view="card">...

Card view is required for Contextual gadgets.
Now you need to upload builded gadgets (all files from folder, where located CtxGadgetEntryPoint.gadget.xml) to FTP or any other web storage, which we specified in Manifest.

Apps Marketplace

Login to Marketplace:
“My Vendor Profile” -> “Create a new listing”;
Check “My product may be directly installed into Google Apps domains”;
Fill “Application Manifest” with content from our Manifest.xml.

So, you’ve created application, now we need to connect it to domain.
Hit “Add it now” button and write your domain, then login with your domain admin credentials and activate application.
Thats all! Open any email and see how it works. Remember, that gadgets have very solid cache and it can take some time for your changes to be accepted, even with ?nogadgetcache=1 parameter.

My sample application searches words, starting with “@” in email body and shows twitter info for these users.

I used Twitter + GWT example by Alex Moffat for this Demo Gadget.
You can find source code here.

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Google App Engine plugin for Netbeans 6.9

I tried to find GAE plugin for netbeans 6.9, but there is only for 6.8. Last Netbeans version doesn’t work with plugin for 6.8, GAE projects just don’t open.
So, I built plugin from source, seems it works, at least project can be opened, built, deployed to App Engine.
You can download it here

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Jar to exe. Tools overview.

Well, you can run java application as: java -jar app.jar in console.
But I’m sure, you agree, that it’s not easy-to-use for users.
So, we can make exe from jar and run it as usual application. I found following tools for this:

This tool costs $75 and has 30-day trial version.
Application converted fine, but when I run the application, there appears message box with thanking for using JEXECreator and suggesting to buy a full version.

Free version works only for console application, Standard Edition costs $14.95. Free trial period is 30 days.
Simple wizard, without many settings. Generated application doesn’t work, a dll is missing, but I didn’t search for it.

Open Source, BSD license. Crossplatform.
It has many settings for all needs. Minimal settings for working application are: exe/jar paths, minimal JRE version, type: console/GUI.
You can make launch4j config and generate exe automatically using ant or maven.

My choice is launche4j! It’s Open Source and allows to automate converting process.

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How to parse mime message using mime4j library

There is example how to use mime4j lib. See comments below.

package com.mozgoweb.mail.test;

import java.util.ArrayList;
import org.apache.james.mime4j.message.BinaryBody;
import org.apache.james.mime4j.message.BodyPart;
import org.apache.james.mime4j.message.Entity;
import org.apache.james.mime4j.message.Message;
import org.apache.james.mime4j.message.Multipart;
import org.apache.james.mime4j.message.TextBody;
import org.apache.james.mime4j.parser.Field;

 * @author Denis Lunev <>

public class TestParser {

    private StringBuffer txtBody;
    private StringBuffer htmlBody;
    private ArrayList<BodyPart> attachments;

     * @param fileName
    public void parseMessage(String fileName) {
        FileInputStream fis = null;

        txtBody = new StringBuffer();
        htmlBody = new StringBuffer();
        attachments<BodyPart> = new ArrayList();

        try {
            //Get stream from file
            fis = new FileInputStream(fileName);
            //Create message with stream from file
            //If you want to parse String, you can use:
            //Message mimeMsg = new Message(new ByteArrayInputStream(mimeSource.getBytes()));
            Message mimeMsg = new Message(fis);

            //Get some standard headers
            System.out.println("To: " + mimeMsg.getTo().toString());
            System.out.println("From: " + mimeMsg.getFrom().toString());
            System.out.println("Subject: " + mimeMsg.getSubject());

            //Get custom header by name
            Field priorityFld = mimeMsg.getHeader().getField("X-Priority");
            //If header doesn't found it returns null
            if (priorityFld != null) {
                //Print header value
                System.out.println("Priority: " + priorityFld.getBody());

            //If message contains many parts - parse all parts
            if (mimeMsg.isMultipart()) {
                Multipart multipart = (Multipart) mimeMsg.getBody();
            } else {
                //If it's single part message, just get text body
                String text = getTxtPart(mimeMsg);

            //Print text and HTML bodies
            System.out.println("Text body: " + txtBody.toString());
            System.out.println("Html body: " + htmlBody.toString());

            for (BodyPart attach : attachments) {
                String attName = attach.getFilename();
                //Create file with specified name
                FileOutputStream fos = new FileOutputStream(attName);
                try {
                    //Get attach stream, write it to file
                    BinaryBody bb = (BinaryBody) attach.getBody();
                } finally {

        } catch (IOException ex) {
        } finally {
            if (fis != null) {
                try {
                } catch (IOException ex) {

     * This method classifies bodyPart as text, html or attached file
     * @param multipart
     * @throws IOException
    private void parseBodyParts(Multipart multipart) throws IOException {
        for (BodyPart part : multipart.getBodyParts()) {
            if (part.isMimeType("text/plain")) {
                String txt = getTxtPart(part);
            } else if (part.isMimeType("text/html")) {
                String html = getTxtPart(part);
            } else if (part.getDispositionType() != null && !part.getDispositionType().equals("")) {
                //If DispositionType is null or empty, it means that it's multipart, not attached file

            //If current part contains other, parse it again by recursion
            if (part.isMultipart()) {
                parseBodyParts((Multipart) part.getBody());

     * @param part
     * @return
     * @throws IOException
    private String getTxtPart(Entity part) throws IOException {
        //Get content from body
        TextBody tb = (TextBody) part.getBody();
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        return new String(baos.toByteArray());

     * @param args
    public static void main(String[] args) {

        String eml = "message.eml";

        TestParser parser = new TestParser();

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How to fix GWT-ext: java.lang.OutOfMemoryError: Java heap space

If you try to run application with gwt-ext on Netbeans, you can face memory problem: GWT-ext: java.lang.OutOfMemoryError: Java heap space
We need to increase java heap for the project.
Simple to fix it:
in %project_home/nbproject/build-gwt.xml after this line:

<arg value="${gwt.module}"/>

just put following (you can put more, then 512mb):

<jvmarg value="-Xmx512m"/>


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How to switch off axis logging?

If you working with axis, you know, that it generates huge batch of debug/logging information into console or log file.

You can switch it off just putting into


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