java - 在 ANTLR 3 中，如何在运行时而不是提前生成词法分析器(和解析器)？

Question

我想在运行时生成一个 antlr 词法分析器——也就是说，生成语法并在运行时从语法生成词法分析器类及其支持位。我很高兴将它提供给 java 编译器，它可以在运行时访问。

Answer 1

这是一种快速而肮脏的方法:

1. 生成一个组合 (!) ANTLR 语法 .g 文件，给定一个字符串作为语法源，
2. 并从这个 .g 文件创建一个解析器和词法分析器，
3. 编译这些 Parser 和 Lexer .java 文件，
4. 创建解析器和词法分析器类的实例并调用解析器的入口点。

主程序.java

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);
    }
}

在像这样编译和运行之后(在 *nix 上):

java -cp .:antlr-3.2.jar Main "a b    c"

或在 Windows 上

java -cp .;antlr-3.2.jar Main "a b    c"

，产生以下输出:

ANY=aANY=bANY=c