我想在运行时生成 antlr 词法分析器 - 也就是说,生成语法并从语法生成词法分析器类及其在运行时的支持位。我很高兴将它输入到 java 编译器中,它可以在运行时访问。
这是一种快速但肮脏的方法:
- 生成一个combined(!)ANTLR 语法
.g
给定一个字符串作为语法源的文件,
- 并由此创建一个解析器和词法分析器
.g
file,
- 编译这些解析器和词法分析器
.java
files,
- 创建 Parser 和 Lexer 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);
}
}
编译并运行后(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=a
ANY=b
ANY=c
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