One Reason to Use EGL: External Types

Whew! I just finished working on a major software feature for my ultra-conservative corporate customer. It provides me with one great reason to use EGL, and specifically, the EGL Development Toolkit (EDT).

I was asked to do the (seemingly) impossible: Duplicate an existing process to create form letters. A few thousand different forms needed to be converted to the new process. While BIRT might have been a general solution to the problem of producing PDFs, there wasn't enough time. I've used BIRT successfully. Generally, I would recommend it. But, designing a few thousand BIRT reports didn't seem to be the right answer.

I used EGL to prototype the PDF generation process. While the development environment was strictly Rational Business Developer, I chose EDT as the tool to build the prototype. And, I'm really glad I did. EDT provides a New | External Type feature, to generate external types from an existing Java library. I imported the iTextPdf library (at www.itextpdf.com). I bought the electronic book: iText in Action.

Within a few minutes, I generated my first PDF. It wasn't much. Writing the code in EGL made it easy to think about the problem in high-level, business-logic terms. I was able to change my mind several times while exploring different designs without the complexity of refactoring Java source code. And yet, external types enable me to use the off-the-shelf iTextPdf library, with all of its power to read and write PDFs.

I connected my PDF generator to a frame library (Framing Software, XVCL) to store key-value pairs in an SQL database. In this specific case, an analysis of a few thousand forms showed a very distinctive pattern and consistency of purpose for the form letters. Knowing exactly what needed to be produced, I was able to create a custom form letter editor. The letter editor provides a mechanism for variable substitution (lifted directly from Apache Ant).

And then, it hit me. The original form letters were composed with Microsoft Word and stored in an open document format. Tapping again into the power of EGL and external types, I imported the text (but not formatting) of the existing form letters into the frame table, using an EGL business logic library. With the text of the form letter in the editor, it was (relatively) quick and easy to add formatting to recreate the original form.

Importing from Microsoft Word to a BIRT report is beyond my technical skill at the moment. This turned out to be the right answer to the specific problem facing the customer. They needed a new way of generating form letters in their production system and, with demands from their customers, they only had thirty days to do it.

Working with EGL alone, I wouldn't be able to finish the project. And working with Java alone, I wouldn't be able to quickly build a succession of prototypes, trying and working through different design ideas.

The best design was selected and imported into Rational Business Developer. While the syntax is similar, EGL written with EDT did not simply drop into the customer's version of RBD. It had to be reworked, especially lack of support for a question mark (?) at the end to indicate a nullable type. At the end of thirty days, end-users were generating customizable PDFs using production web application.

Now, that's a good reason to use EGL. What do you think?

Essential EGL+Batch - Companion Book

The 2013-05-23 draft of a companion book for the Essential EGL+Batch video series is now available in PDF format. It includes instructions for installing EGL Development Tools on Linux, OS X and Windows. It includes the source code for lessons 1 thru 22. It includes additional information on EGL not presented in the video series.

Essential EGL+Batch - Introduction to Eclipse

Introduction to Eclipse is the first session of our Essential EGL+Batch training course. It features EGL Development Tools version 0.8.

This session describes the essential features of Eclipse, such as workspace, perspectives and views. It is based upon the following three documents:

1. Presentation. For on-site, an instructor uses a presentation called 1 Introduction to Eclipse. 
2. Self-study guide. For our on-line students, this 1.0 Introduction to Eclipse self-study guide provides the instructor's notes for the presentation.
3. Exercise. The exercise is 1.1 Introduction to Eclipse.

Thanks,

Essential EGL+Batch - Source Code 1 thru 22

Source code for lessons 1 through 22 is now available in an archive file. This includes both the EGL and Java source code.

eglprogram-22.zip

For more information on importing the source code, see also Essential EGL+Batch - Archive File.

Essential EGL+Batch - Archive File

Backup your EGL project by exporting it to an archive file. In a new workspace, restore your EGL project by importing an archive file.

Essential EGL+Batch - Lesson 22 Connection Properties

Get properties from an open connection to a JDBC-compatible database. Configure a database connection for (1) your Eclipse workbench, (2) your EGL project and (3) your EGL program. Use the Database Development perspective to create a new database connection. Edit the EGL Deployment Descriptor (.egldd) file to add a database (SQL/JDBC) resource. Create a library called ConnectionLib to connect to a database. This lesson does not describe how to install database software or create a database.

Essential EGL+Batch - Lesson 21 Arguments

Essential EGL+Batch - Lesson 21 Arguments is now available on my YouTube channel. Use a Java class and external type to get command-line arguments. Pass arguments from a command-line to an EGL batch program.

Essential EGL+Batch - Lesson 20 Delegate Field

Essential EGL+Batch - Lesson 20 Delegate Field is now available on my YouTube channel. A delegate can be a field in a record. Use demo functions from lessons 4 thru 19.

Essential EGL+Batch - Lesson 19 External Type is now available on my YouTube channel. Define and use an external type in an EGL program. Create a Java class called JavaSystem to get a complete list of property names for Java system properties.

Essential EGL+Batch - Lesson 18 Custom Property

Essential EGL+Batch - Lesson 18 Custom Property is now available on my YouTube channel. Define a custom property on the command line and get a custom property in an EGL program. Essential EGL+Batch is a video series featuring EGL Development Tools (EDT) version 0.8.

Essential EGL+Batch - Lesson 17 System Property

Essential EGL+Batch - Lesson 17 System Property is now available on my YouTube channel. When EGL generates to Java, the standard Java system properties, such as “os.name” and “user.name”, are available to your EGL program. Essential EGL+Batch is a video series featuring EGL Development Tools (EDT) version 0.8.

Essential EGL+Batch - Lesson 16 Log Exception

Essential EGL+Batch - Lesson 16 Log Exception is now available on my YouTube channel. When it is thrown, log an exception on the console. Essential EGL+Batch is a video series featuring EGL Development Tools (EDT) version 0.8.

Essential EGL+Batch - Java Control Panel

Essential EGL+Batch - Java Control Panel is now available on my YouTube channel. Which version of Java is installed? Explore the Java Control Panel. This video is part of the Essential EGL+Batch series. Featuring Java 6 on Windows.

Essential EGL+Batch - Installing EGL Development Tools on Mac OS X

Essential EGL+Batch - Installing EGL Development Tools on Mac OS X is now available on my YouTube channel. Download and install Eclipse Indigo (3.7) on Mac OS X (Lion). Install EGL Development Tools (EDT) with the Install New Software feature of Eclipse. Essential EGL+Batch is a video series featuring EGL Development Tools (EDT) version 0.8.

Essential EGL+Batch - Installing EGL Development Tools on Windows

Essential EGL+Batch - Installing EGL Development Tools on Windows is now available on my YouTube channel. Download and install EGL Development Tools (EDT) version 0.8.1 on Microsoft Windows XP (32-bit). Essential EGL+Batch is a video series featuring EGL Development Tools (EDT) version 0.8.

Essential EGL+Batch - Lesson 15 Exception

Essential EGL+Batch - Lesson 15 Exception is now available on my YouTube channel. Handle an exception with try/onException. Throw an exception with throw. Essential EGL+Batch is a video series featuring EGL Development Tools (EDT) version 0.8.

Essential EGL+Batch - Lesson 14 Record Array

Essential EGL+Batch - Lesson 14 Record Array is now available on my YouTube channel. Work with an array of records. Use a fixed-length record to generate a report. Essential EGL+Batch is a video series featuring EGL Development Tools (EDT) version 0.8.

Essential EGL+Batch - Lesson 13 Nested Record

Essential EGL+Batch - Lesson 13 Nested Record is now available on my YouTube channel. Create and use a nested record, a record within a record. Essential EGL+Batch is a video series featuring EGL Development Tools (EDT) version 0.8.

Essential EGL+Batch - Lesson 12 Fixed-Length Record

Essential EGL+Batch - Lesson 12 Fixed-Length Record is now available on my YouTube channel. Convert a simple fixed-length record to a normal EGL record. Essential EGL+Batch is a video series featuring EGL Development Tools (EDT) version 0.8.

Essential EGL+Batch - Lesson 11 Record

Essential EGL+Batch - Lesson 11 Record is now available on my YouTube channel. Create and use a simple record. Essential EGL+Batch is a video series featuring EGL Development Tools (EDT) version 0.8.