Simple scripting langauge based on ANTLR4 that compiles into Java

Language Reference

• Variable assignment

  • @name = <value>
    • @stringVariable = "hello world"
    • @daysInWeek = 7
    • @boolVal = True

• Conditionals

  • IF @boolVal
       <Do stuff>
    END
    
    

• Loops

  • FOREACH @item IN @array
      <statements>   
    END
    
    

• Function call

  • fnName{namedArg1=@variable1, namedArg3=@variable3}

• Lambda expr

  • @param1 = "text"
    @param2 = 456789
    @fn = FUNCTION @param1, @param2 
      <statements>
    END
    
    
    

API

The compiler will generate only method bodies from the script. annotate method that you wish to generate

    public abstract class Test {
        @ScriptMeta.ScriptTarget
        public abstract Result test();
    }

To call java method from the script first define an annotated proxy

    @ScriptMeta.Function("print")
    public class PrintFn {
        @ScriptMeta.Handler
        public void print(@ScriptMeta.NamedParam("val") Object o, @ScriptMeta.NamedParam("int") int i) {
            System.out.println(o);
            System.out.println(i);
        }
    }

and provide its instanceto the context via add the builder

        NTScript context = new NTScript.Builder()
                .package_("cz.neumimto.test")
                .debugOutput("/tmp/test")
                .implementingType(Test.class)
                .withEnum(Result.class)
                .add(List.of(new PrintFn()))
                .setClassNamePattern("aaa")
                .build();

    Class aClass = script.parseScript("""
        @textVariable = "abcd"
        print{val=@textVariable}  
        RETURN Result.OK
    """);

The compiler will generate class as follows:

public class aaa0 extends Test {
     
      public PrintFn PrintFn;

      public Result test() {
            String var1 = "abcd";
            PrintFn.print(var1, null) ;
           return Result.OK
      }
}

• After calling constructor you should inject the PrintFn field.
• If you are using some sort of DI such as Guice you can use Builder methods classAnnotations and fieldAnnotations for simpler initialization.