使用ANTLR爲java源代碼生成抽象語法樹

Question

如何從java src代碼生成AST使用ANTLR？
有幫助嗎？

Answer 1

的setps使用antlr4生成Java SRC AST是：

1. 安裝antlr4你可以使用this鏈接來做到這一點。安裝後下載JAVA grammar from here。

2. 現在使用命令生成Java8Lexer和Java8Parser：

   antlr4 -visitor Java8.g4

3. 這將生成多個文件，如Java8BaseListener.javaJava8BaseVisitor.javaJava8Lexer.javaJava8Lexer.tokensJava8Listener.javaJava8Parser.javaJava8.tokensJava8Visitor.java

使用此代碼生成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)); 
      } 
     } 
    } 
} 

你做的編碼就可以使用gradle這個來構建你的項目，也可以在你的項目目錄下載antlr-4.7.1-complete.jar並啓動編譯之後。

如果你想在一個DOT文件輸出，使u能可視化的AST，那麼你可以參考this QNA郵寄或直接引用這個repository在我所使用gradle這個來構建項目。

希望這會有所幫助。 :)

Answer 2

OK，這裏的步驟：

1. 去ANTLR Site現在下載最新版本是4.7
2. 從here下載Java.g和JavaTreeParser.g文件。

3. 執行如下命令：

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

4. 5的文件將被生成：

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

使用這個Java代碼來生成抽象語法樹，並打印：

 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); 
     } 
    } 
}