I did find an answer to my question: Barts answer is exactly why I need, but it does not function (see below).
Please can some one either give me a working example or show me the where I am going wrong to implement Barts answer?
This is what I get for the other answer, I get the hereunder error from “part 4”
Lexer lexer = (Lexer)Class.forName(grammarName + "Lexer").newInstance();
I’ve got antlr3.4 complete and JDK libraries. I created it as package createclass; yet I find the answer strange as the class to create has no package???
So I tried adding to the string:
"@lexer::header {\n" +
" package createclass;\n" +
"} \n" +
"@parser::header {\n" +
" package createclass;\n" +
"}\n" +
But still no change.
Here’s the output:
debug:
Exception in thread "main" java.lang.ClassNotFoundException: TLexer
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:169)
at createclass.Createclass.main(Createclass.java:61)
Java Result: 1
BUILD SUCCESSFUL (total time: 31 seconds)
The example code given is:
import java.io.*;
import javax.tools.*;
import java.lang.reflect.*;
import org.antlr.runtime.*;
import org.antlr.Tool;
public class Main {
public static void main(String[] args) throws Exception {
// The grammar which echos the parsed characters to theconsole,
// skipping any white space chars.
final String grammar =
"grammar T; \n" +
" \n" +
"parse \n" +
" : (ANY {System.out.println(\"ANY=\" + $ANY.text);})* EOF \n" +
" ; \n" +
" \n" +
"SPACE \n" +
" : (' ' | '\\t' | '\\r' | '\\n') {skip();} \n" +
" ; \n" +
" \n" +
"ANY \n" +
" : . \n" +
" ; ";
final String grammarName = "T";
final String entryPoint = "parse";
// 1 - Write the `.g` grammar file to disk.
Writer out = new BufferedWriter(new FileWriter(new File(grammarName + ".g")));
out.write(grammar);
out.close();
// 2 - Generate the lexer and parser.
Tool tool = new Tool(new String[]{grammarName + ".g"});
tool.process();
// 3 - Compile the lexer and parser.
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
compiler.run(null, System.out, System.err, "-sourcepath", "", grammarName + "Lexer.java");
compiler.run(null, System.out, System.err, "-sourcepath", "", grammarName + "Parser.java");
// 4 - Parse the command line parameter using the dynamically created lexer and
// parser with a bit of reflection Voodoo :)
Lexer lexer = (Lexer)Class.forName(grammarName + "Lexer").newInstance();
lexer.setCharStream(new ANTLRStringStream(args[0]));
CommonTokenStream tokens = new CommonTokenStream(lexer);
Class<?> parserClass = Class.forName(grammarName + "Parser");
Constructor parserCTor = parserClass.getConstructor(TokenStream.class);
Parser parser = (Parser)parserCTor.newInstance(tokens);
Method entryPointMethod = parserClass.getMethod(entryPoint);
entryPointMethod.invoke(parser);
}
}
My guess is that you’re using an IDE for this, and don’t have your classpath set properly. The demo from my answer works (also using v3.4). Here’s what I just did:
I copied the file
Main.javain a directory (~/Temp/demo, in my case) and opened a shell in this directory and did the following:(the
>is output printed to the console)