使用ANTLR为java源代码生成抽象语法树

Question

如何使用ANTLR从java src代码生成AST？
任何帮助？

Answer 1

好的,这是步骤:

1. 转到ANTLR站点并下载最新版本
2. 从这里下载文件Java.g和JavaTreeParser.g文件.

3. 运行以下命令:

   java -jar antlrTool Java.g
   java -jar antlrTool JavaTreeParser.g
   

4. 将生成5个文件:

   1. Java.tokens
   2. JavaLexer.java
   3. JavaParser.java
   4. JavaTreeParser.g
   5. JavaTreeParser.tokens

使用此java代码生成抽象语法树并打印它:

        String input = "public class HelloWord {"+
                   "public void print(String r){" +
                   "for(int i = 0;true;i+=2)" +
                   "System.out.println(r);" +
                   "}" +
                   "}";

    CharStream cs = new ANTLRStringStream(input);
    JavaLexer jl = new JavaLexer(cs);

    CommonTokenStream tokens = new CommonTokenStream();
    tokens.setTokenSource(jl);
    JavaParser jp = new JavaParser(tokens);
    RuleReturnScope result = jp.compilationUnit();
    CommonTree t = (CommonTree) result.getTree();

    CommonTreeNodeStream nodes = new CommonTreeNodeStream(t);

    nodes.setTokenStream(tokens);

    JavaTreeParser walker = new JavaTreeParser(nodes);

    System.out.println("\nWalk tree:\n");

    printTree(t,0);


    System.out.println(tokens.toString());

    }

public static void printTree(CommonTree t, int indent) {
    if ( t != null ) {
        StringBuffer sb = new StringBuffer(indent);
        for ( int i = 0; i < indent; i++ )
            sb = sb.append("   ");
        for ( int i = 0; i < t.getChildCount(); i++ ) {
            System.out.println(sb.toString() + t.getChild(i).toString());
            printTree((CommonTree)t.getChild(i), indent+1);
        }
    }
}

Answer 2

使用antlr4生成java src AST的setps是：

1. 安装antlr4，您可以使用此链接来执行此操作。
2. 安装后从这里下载JAVA语法。

3. 现在使用以下命令生成 Java8Lexer 和 Java8Parser：

   antlr4 -visitor Java8.g4

4. 这将生成几个文件，例如Java8BaseListener.java Java8BaseVisitor.java Java8Lexer.java Java8Lexer.tokens Java8Listener.java Java8Parser.java Java8.tokens Java8Visitor.java

使用此代码生成 AST：

import java.io.File;
import java.io.IOException;

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 {

    public static String readFile() throws IOException {
        File file = new File("path/to/the/test/file.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.classDeclaration();

        printAST(ctx, false, 0);
    }

    private static void printAST(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()];
            for (int i = 0; i < indentation; i++) {
                System.out.print("  ");
            }
            System.out.println(ruleName + " -> " + ctx.getText());
        }
        for (int i = 0; i < ctx.getChildCount(); i++) {
            ParseTree element = ctx.getChild(i);
            if (element instanceof RuleContext) {
                printAST((RuleContext) element, verbose, indentation + (toBeIgnored ? 0 : 1));
            }
        }
    }
}

完成编码后，您可以使用 gradle 构建项目，也可以在项目目录中下载antlr-4.7.1-complete.jar并开始编译。

如果您想要 DOT 文件中的输出，以便可以可视化 AST，那么您可以参考此QnA 帖子或直接参考此存储库，我在其中使用 gradle 构建项目。

希望这可以帮助。:)