This session discusses building Domain Specific Languages and DSL-style code in Java, Groovy, and Ruby. It discusses the different types of DSLs, details on how to implement them in Java, Groovy, and Ruby, and example problem domains where DSLs make sense.

You've heard all the hype for the past couple of years: Domain Specific Languages (DSLs) are going to take over the world. This session demystifies this topic in 2 ways: by providing concrete definitions for styles and applicability of DSLs and showing how to implement these different styles. I build up definitions for the different types of DSLs in static (Java) and dynamic (Groovy and Ruby) languages. Then, I discuss building DSLs as internal (i.e., built on top of an underlying language) and external (built using a preprocessor or grammar), with examples of each. Throughout this session, I discuss the applicability of this style of development and show targeted examples. I discuss fluent interfaces and techniques for building them, including problems. Incidentally, I show some cool language features of both Groovy and Ruby that make building DSLs easier in those languages.

Session Topics:

• Why DSLs
• Abstraction
• Internal vs. External DSLs
• Fluent Interfaces
• Building Blocks
• Internal DSLs
• In Java
• In Groovy
• In Ruby
• The Stopping Problem
• Best Practices and Applications