Tuesday May 28, 2013

Virtual Developer Day: Java ME, SE, and EE

It's an exciting time in the Java Jungle! There are a lot of things going on "in Java" right now, and as a result, there are several free webinars scheduled to provide introductions to technologies and concepts you might want to know a bit more about. Just recently, I mentioned the upcoming Introducing Java EE 7 webcast, and now there's another one you'll probably be very interested to attend. The best part(s)? You can attend from your home or workplace and it's completely free! The worst part? You may struggle to decide which track to take - they're all that good.

For this four-hour Virtual Developer Day, here are the tracks and their topics:

Separate dates/times are offered for western and eastern hemispheres; please click this link to learn more and register.

Keep the Java flowing,

Wednesday May 22, 2013

Java EE 7: Get Ready!

With the recent approval of the Java EE 7 platform JSR, Java EE 7 is on its way!

There will be two webinars to introduce new features and give you an idea of what all the buzz is about. You can access this feature-packed event from your own desk, jump in when you can and step away when you need to do so. Registering once gets you access to both days, so you can sign up now and nail down your schedule as the time approaches.

What will you see in this online event ?
  • Business Keynote (Hasan Rizvi and Cameron Purdy)
  • Technical Keynote (Linda DeMichiel)
  • Breakout Sessions on different JSRs by specification leads
  • Live Chat
  • Lots of Demos
  • Community, Partner, and Customer video testimonials

Follow this link to sign up, or click on the images above/below. "See" you there!

All the best,

Tuesday Feb 26, 2013

How to "Pretty Up" Your JavaFX TableViews

One day you're a happy JavaFX developer, cranking out applications and blissfully providing your application's users with table after table of rich textual information. The next day it happens: your users approach you and ask if there's a way to include a thumbnail of each part in the inventory list. Or a small photo in the contact list/personnel roster. Or a snapshot/graph of the latest conditions for each monitored sensor or weather camera. So now what?

PropertyValueFactory, a convenience implementation of the Callback interface, is typically used to handle the work involved with populating all cells within a single TableColumn. As long as you provide the name of a valid property to the PropertyValueFactory constructor and set the TableColumn's CellValueFactory to the resulting PropertyValueFactory, the cell is populated, TableView adds an observer to the value, and life moves merrily along.

Adding a graphical element to a TableView isn't much harder, actually. The TableColumn's CellFactory handles rendering of the cell's contents, so if you want to place something other than textual content in the cell, you'll need to also set the TableColumn's CellFactory to one of your liking and override the updateItem() method. Let's take a look at a quick example.

I'd always intended to create some small-but-useful Twitter utilities and hadn't really had the opportunity, but a simple Twitter client provides a perfect demonstration of this capability. Here is an example of what a "feed" interface might look like:

For this TableView example, there are only two columns:

  • one for the user, showing the user's picture, name, and screen name
  • one for the tweet

The tweet's text is simply a string property of each MTweet object, but the user information comes from several properties of the MTweet object's associated MUser object. The MTweet's text is properly assigned to the cell's text property per the discussion above, but what about the user information? Per the JavaFX 2.2 docs,

Because by far the most common use case for cells is to show text to a user, this use case is specially optimized for within Cell. This is done by Cell extending from Labeled. This means that subclasses of Cell need only set the text property, rather than create a separate Label and set that within the Cell. However, for situations where something more than just plain text is called for, it is possible to place any Node in the Cell graphic property. Despite the term, a graphic can be any Node, and will be fully interactive. For example, a ListCell might be configured with a Button as its graphic. The Button text could then be bound to the cells item property. In this way, whenever the item in the Cell changes, the Button text is automatically updated.

To display the tweet's text in the "Text" column of our table, a couple lines of code does all that is necessary:

In order to bundle the user information and place it within a single cell, we set the "User Info" column's CellValueFactory in similar fashion to our text column above:

And then we set that column's CellFactory to something along the order of this:

For each cell in that TableColumn, updateItem is called with that cell's contents as the "item", the first parameter. Within our example above, we create a VBox, populate it with the user's photo (Image, via ImageView), name (String) and screen name (String), do a bit of formatting, and assign the VBox to the cell's graphic property. And with that, we're off and running. :-)

There is much more you can do, and this should get the ideas flowing. Here's to prettier apps (better optics?) and happier users!

All the best,

<<< UPDATE 1 >>>

Jonathan Giles, JavaFX team UI Controls tech lead, made a few suggestions for improving the efficiency of the code used above. The points he made were excellent, and I wanted to provide an update that shows revised code that incorporates them. I did leave the original code above, as I'm hoping it helps make a clearer path for those implementing similar code for the first time.

In order to override the TableCell constructor, we'll extend the particular TableCell<MTweet, MUser> class. Doing so allows us to create the VBox, Labels, and ImageView used in our composite user cell once per cell, rather than each time updateItem() is called. While we're at it, we'll also perform formatting/assignment duties in the constructor and avoid repeating those calls. Here is the new derivative class:

Creating the new UserTableCell class means we can update our setCellFactory() method call for our user info column like so:

Thanks to Jonathan Giles (@JonathanGiles) for the suggestions!

All the best,

<<< UPDATE 2 >>>

One more update! This time using an anonymous inner class for the column's cell factory. Same basic functionality, but this is perhaps the tidiest option.

Options are good, as they say...  :-)

All the best,

Monday Jan 14, 2013

Secure Email from Java

I've been working recently with a client to do some rather useful things with notifications, and one of them involved sending a secure email from within a Java program. We encountered some interesting (translation: weird!) challenges, and in overcoming them, I worked out a reasonably straightforward path through the minefield. If you've been thinking about secure-email-enabling your Java app but aren't sure where to start, hopefully this will serve as a fairly quick and mostly painless primer.  :-)

The Problem

Let me first say that if you only want to send a plain-text email from Java, there are ways to do that without much fuss and without any external players. If you want to sign or encrypt your emails, though, you'll need a couple of extra components:
1. a digital certificate (private/public key pair issued by a recognized Certificate Authority, or "CA") and
2. a means of using the certificate to sign and/or encrypt the email

The goal is to digitally sign an email to assure recipients that the sender of the mail is indeed me (or you, if you're following along at work/home). Let's get started!

Getting Your Tools in Order

Getting a Certificate

First, we have to have a digital certificate. If you already have one, you can skip this step...but if not, StartSSL offers free user/email certificates for personal use. Just point your browser to the StartSSL site and click the large button labeled "Sign-up". You'll need to provide them some information, enter the verification code they email to the address you provide, and they do the rest...including installing your new cert and the certificate chain into your web browser.

Freeing the Certificate from your Browser

Perhaps the easiest way to use a certificate is to store it (keys, certificate chain) in a Java Keystore (jks). Extracting your shiny new certificate from your browser is a relatively easy (albeit drawn-out) process. From your browser, export your certificate, including private key. This will produce a .pfx file, which is a PKCS12 keystore. From Chrome, you simply:
  1. Click on the Wrench (or Lines) icon in the upper-right corner
  2. Select "Settings" from the menu
  3. "Show advanced settings..." at the bottom of the page
  4. Scroll down to the section labeled "HTTPS/SSL"
  5. Click the "Manage certificates..." button to display your certificates.
Then, from the certificates window:
  1. Select the target certificate and click the "Export..." button
  2. Click "Next" from the Export Wizard window
  3. Choose "Yes, export the private key" and click "Next"
  4. Under the "Personal Information Exchange - PKCS #12 (.PFX)" entry, select the options to "Include all certificates in the certification path if possible" and "Export all extended properties" (NOTE: Do NOT choose to "Delete the private key if the export is successful". No no no!) and click "Next"
  5. Enter a password (twice) and click "Next"
  6. Provide a path/filename for the export and click "Next", and finally...
  7. Confirm the export options and click "Finish".
Now that we've liberated your cert from the browser, let's make it usable by our (non-browser) Java program.

Creating a Java Keystore

The fastest, easiest way I've found to convert a .pfx file to a .jks (Java Keystore) file is with the Oracle 11g database client. The database client can be downloaded by following this link, selecting the "See All" link to the right of your listed operating system, and choosing the 11g client from the OS-specific download page. Once it's downloaded and installed, you're ready to proceed.

Like the .pfx file, the Oracle wallet is a PKCS12 keystore, and the orapki utility (and other tools) included with the database client can be used to manipulate it...as long as it thinks it's dealing with an Oracle wallet. To make that happen, simply rename the .pfx file to ewallet.p12. Since we aren't dealing with the Oracle Wallet Manager, we don't have to worry about meeting OWM's password criteria or other niceties. Yes, that really is all there is to it!

Now, to make a Java Keystore. To do that, you'll need to open a command prompt and do the following tasks:
  1. Create an ORACLE_HOME environment variable that points to the install location of the Oracle client
  2. Run the following command, pointing to the orapki utility under %ORACLE_HOME%\bin (in Windows) or $ORACLE_HOME/bin (Mac/Linux/UNIX):
orapki wallet pkcs12_to_jks -wallet <wallet_directory> -pwd <wallet_password> -jksKeyStoreLoc <java_key_store_path_and_filename> -jksKeyStorepwd <jks_password>

You should now have a brand new Java KeyStore! You can verify its contents with the OpenSSL keytool utility:
keytool -list -keystore <java_key_store>

Now that we have our credentials in order, on to the Java side of things!

Building the Solution

There are several Java libraries available that aid in signing and/or encrypting email. Of the non-commercial options I found, all use the Bouncy Castle Crypto API and libraries as their underpinnings. Bouncy Castle (BC) may have a funny name, but it's all business with regard to encryption.

At a very high level, you need to do the following things to create/send a signed email:
  1. Provide the email "essentials": SMTP server host & port, email addresses (sender & receiver), a subject, content, and the sending user's password
  2. Add BC as a new crypto provider
  3. Retrieve the cert from your Java Keystore
  4. Create and sign the email using the BC API/libraries
  5. Send the email
There is much more you can do of course, but these are the "must-haves".

In preparation for developing our secure email module, I created a proof of concept (BCCrypTool) by marrying a Java email program I'd written previously and some BC sample code...code reuse at its lowest level, but still good for the environment. :-) What you see here in my GitHub repo is a bit of streamlined Java code that should be pretty easy to repurpose. Please feel free to take a copy and do just that, and if you make significant changes/improvements and are able and inclined to share them, please feel free to do that as well. Sharing is caring.  :-)

A quick note on libraries. You'll need the following to make this work:
And from Bouncy Castle, the following:
  • The BC provider library (bcprov-jdk15on-147.jar)
  • The BC S/MIME library (bcmail-jdk15on-147.jar)
  • The BC security library (bcpkix-jdk15on-147.jar)
There are other BC libraries available here if you'd like to take things even further.

All the best to you in your Java secure email adventures!


Saturday Nov 10, 2012

Polishing the MonologFX API

Earlier this week, I released "into the wild" a new JavaFX 2.x dialog library, MonologFX, that incorporated some elements of DialogFX and new features I'd been working on over time. While I did try to get the API to a point of reasonable completion (nothing is ever truly "finished", of course!), there was one bit of functionality that I'd included without providing any real "polish": that of the button icons.

Good friend and fellow JFXtras teammate José Pereda Llamas suggested I fix that oversight and provide an update (thanks much, José!), thus this post. If you'd like to take a peek at the new streamlined syntax, I've updated the earlier post; please click here if you'd like to review it. If you want to give MonologFX a try, just point your browser to GitHub to download the updated code and/or .jar.

All the best,


The Java Jungle addresses all things Java (of course!) and any other useful and interesting tools & platforms that help us GET IT DONE. "Artists ship," after all. :)

Your Java Jungle guide is Mark Heckler, a Software Architect/ Engineer and Oracle Developer Evangelist with development experience in numerous environments. Mark's current pursuits and passions all revolve around Java, the Cloud, & the IoT, and leave little time to blog or tweet - but somehow, he finds time to do both anyway.

Mark lives with his very understanding wife in the St. Louis, MO area.

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