Many times I've seen the necessity for parser creation. There are many examples where we need a parser for automation of analysis, diagram creation, etc.
Most common libraries for it :
- antlr
- javaparser
- eclipse jdt
- custom
Own example: https://github.com/devwebcl/eclipse-cdt-poc
Examples :
- Documenting your architecture: Wireshark, PlantUML and a REPL to glue them all
- Your Program as a Transpiler
- Federico Tomassetti has several DSL examples.