grule-rule-engine is heavily using ANTLR4 lexer/parser to parse GRL rules. The parser
.go
files were generated by ANTLR4 tools program.
The version currently used can be downloaded here (antlr-4.13.1-complete.jar). Or you can always go to ANTLR4 download page.
Download the .jar
file and place it somewhere a directory.
Yes, you need Java for this. You can download java from Oracle's Java Download Page. Install java and you're ready to work with ANTLR4.
alias antlr='java -jar /path/to/downloaded/antlr-4.13.1-complete.jar'
To build ANTLR4's golang listener or visitor, go to the directory where you
have your antlr4 grammar .g4
file. And then execute the following command.
antlr -Dlanguage=Go -o parser -package grulev3 -lib . -listener -visitor grulev3.g4
With GNU Make installed, it is also possible to use the Makefile in the antlr
directory.
The command make clean
can be used to remove the generated content of the
antlr/parser/grulev3
directory.
Then, it is possible to generate the parser code with:
make ANTLR="java -jar /path/to/downloaded/antlr-4.13.1-complete.jar"