CODEWITHSUNDEEP
javaparsingantlr4visitor-pattern
MSS
MSS

Reputation: 3633

Accessing sub context of a rule context in Antlr4 using visitor

I am trying to parse Java class files using Java.g4 grammar and Antlr4. There is a particular parser rule as follows:

classOrInterfaceType
:   Identifier typeArguments? ('.' Identifier typeArguments? )*
;

I am parsing it in my visitor class in this way:

public String visitClassOrInterfaceType(JavaParser.ClassOrInterfaceTypeContext ctx) {
    StringBuilder clsIntr = new StringBuilder("");
    int n = ctx.getChildCount();
    for(int i = 0; i < n; i++){
        TerminalNode id = ctx.Identifier(i);
        if(id!=null){
            clsIntr.append(id.getText()).append(" ");
        }
        TypeArgumentsContext typArgCtx =ctx.typeArguments(i);
        if(typArgCtx!=null){
            String val = this.visitTypeArguments(typArgCtx);
            clsIntr.append(val);
        }
    }
    return clsIntr.toString();
}

Is this correct or there is some other way to do this?

Upvotes: 2

Views: 1339

Answers (1)

Mike Lischke
Mike Lischke

Reputation: 53357

Your approach looks ok, even though that ultimately depends on what you are actually trying to do. My crystal ball tells me you try to reconstruct the original query text by walking the parse tree. However, you can get that much simpler. Each parse context has start and stop members that hold tokens for the parsed text range this context stands for. You could use those to directly get the original text exactly like it was entered (via the token stream and the token's positions).

Upvotes: 1

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