Generate AST in the form of a dot file

The answer i was looking for is answered here by Bart Kiers but for people who want to generate DOT files without modifying the grammar can print a intended syntax tree by taking help from this repository. Since i did not find much documentation on dot generation in ANTLR4 and no other option other than to modify ANTLR3 grammar file, i used Federico Tomassetti example and modified it a little to generate our own DOT file.

You can print a Dot file output by:

import java.io.File; import java.io.IOException; import java.util.ArrayList; import java.nio.charset.Charset; import java.nio.file.Files; import org.antlr.v4.runtime.ANTLRInputStream; import org.antlr.v4.runtime.CommonTokenStream; import org.antlr.v4.runtime.ParserRuleContext; import org.antlr.v4.runtime.RuleContext; import org.antlr.v4.runtime.tree.ParseTree; public class ASTGenerator { static ArrayList<String> LineNum = new ArrayList<String>(); static ArrayList<String> Type = new ArrayList<String>(); static ArrayList<String> Content = new ArrayList<String>(); private static String readFile() throws IOException { File file = new File("resource/java/Blabla.java"); byte[] encoded = Files.readAllBytes(file.toPath()); return new String(encoded, Charset.forName("UTF-8")); } public static void main(String args[]) throws IOException{ String inputString = readFile(); ANTLRInputStream input = new ANTLRInputStream(inputString); Java8Lexer lexer = new Java8Lexer(input); CommonTokenStream tokens = new CommonTokenStream(lexer); Java8Parser parser = new Java8Parser(tokens); ParserRuleContext ctx = parser.compilationUnit(); generateAST(ctx, false, 0); System.out.println("digraph G {"); printDOT(); System.out.println("}"); } private static void generateAST(RuleContext ctx, boolean verbose, int indentation) { boolean toBeIgnored = !verbose && ctx.getChildCount() == 1 && ctx.getChild(0) instanceof ParserRuleContext; if (!toBeIgnored) { String ruleName = Java8Parser.ruleNames[ctx.getRuleIndex()]; LineNum.add(Integer.toString(indentation)); Type.add(ruleName); Content.add(ctx.getText()); } for (int i = 0; i < ctx.getChildCount(); i++) { ParseTree element = ctx.getChild(i); if (element instanceof RuleContext) { generateAST((RuleContext) element, verbose, indentation + (toBeIgnored ? 0 : 1)); } } } private static void printDOT(){ printLabel(); int pos = 0; for(int i=1; i<LineNum.size();i++){ pos=getPos(Integer.parseInt(LineNum.get(i))-1, i); System.out.println((Integer.parseInt(LineNum.get(i))-1)+Integer.toString(pos)+"->"+LineNum.get(i)+i); } } private static void printLabel(){ for(int i =0; i<LineNum.size(); i++){ System.out.println(LineNum.get(i)+i+"[label=\""+Type.get(i)+"\\n "+Content.get(i)+" \"]"); } } private static int getPos(int n, int limit){ int pos = 0; for(int i=0; i<limit;i++){ if(Integer.parseInt(LineNum.get(i))==n){ pos = i; } } return pos; } } 

For a source code like this:

class example{ public static void main(){ int a; a = 5; } } 

Output will be:

digraph G { 00[label="compilationUnit\n classexample{publicstaticvoidmain(){inta;a=5;}}<EOF> "] 11[label="normalClassDeclaration\n classexample{publicstaticvoidmain(){inta;a=5;}} "] 22[label="classBody\n {publicstaticvoidmain(){inta;a=5;}} "] 33[label="methodDeclaration\n publicstaticvoidmain(){inta;a=5;} "] 44[label="methodModifier\n public "] 45[label="methodModifier\n static "] 46[label="methodHeader\n voidmain() "] 57[label="result\n void "] 58[label="methodDeclarator\n main() "] 49[label="block\n {inta;a=5;} "] 510[label="blockStatements\n inta;a=5; "] 611[label="localVariableDeclarationStatement\n inta; "] 712[label="localVariableDeclaration\n inta "] 813[label="integralType\n int "] 814[label="variableDeclaratorId\n a "] 615[label="expressionStatement\n a=5; "] 716[label="assignment\n a=5 "] 817[label="expressionName\n a "] 818[label="assignmentOperator\n = "] 819[label="literal\n 5 "] 00->11 11->22 22->33 33->44 33->45 33->46 46->57 46->58 33->49 49->510 510->611 611->712 712->813 712->814 510->615 615->716 716->817 716->818 716->819 } 

Insert this piece of output in http://viz-js.com/ You will get this as ouput:

You can also pipe the output to ast.dot file by:

java -jar path-to-jar-file.jar > ast.dot 

Now this is not the perfect method but enough for me. :)

Hope this helps.