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.


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:

To add multiply extractors use:

GWT application code

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:

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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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.

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