从JAVA中提取AST并将AST打印到文件中

Question

I'm a beginner to the Java programming language. I want to extract the AST from java source code and print the AST to a file or standard output.

I followed this tutorial to learn how to work with AST. http://www.programcreek.com/2011/01/a-complete-standalone-example-of-astparser/

So according to that the code I have so far is as follows.

import java.util.HashSet;
import java.util.Set;

import org.eclipse.jdt.core.dom.AST;
import org.eclipse.jdt.core.dom.ASTParser;
import org.eclipse.jdt.core.dom.ASTVisitor;
import org.eclipse.jdt.core.dom.CompilationUnit;
import org.eclipse.jdt.core.dom.SimpleName;
import org.eclipse.jdt.core.dom.VariableDeclarationFragment;

public class Test {
    public static void main(String args[]){
        ASTParser parser = ASTParser.newParser(AST.JLS3);
        parser.setSource("public class A { int i = 9;  \n int j; \n ArrayList<Integer> al = new ArrayList<Integer>();j=1000; }".toCharArray());
        //parser.setSource("/*abc*/".toCharArray());
        parser.setKind(ASTParser.K_COMPILATION_UNIT);
        //ASTNode node = parser.createAST(null);


        final CompilationUnit cu = (CompilationUnit) parser.createAST(null);

    }
}

I tried the following code snippet to print it out to the standard output but it didn't give me the result I expected,

System.out.println(cu.getAST().toString());

If somebody could help me to print the AST out to a file it would be a great help.

Thanks in advance.

Answer 1

Here is an example of transforming the AST to JSON . You can modify the JSONStyleASTPrinter.java file to produce XML instead JSON etc.

Based on example from How To Train the JDT Dragon combined.pdf :

private void print(ASTNode node) {
    List properties = node.structuralPropertiesForType();
    for (Iterator iterator = properties.iterator(); iterator.hasNext();) {
        Object descriptor = iterator.next();
        if (descriptor instanceof SimplePropertyDescriptor) {
            SimplePropertyDescriptor simple = (SimplePropertyDescriptor) descriptor;
            Object value = node.getStructuralProperty(simple);
            System.out.println(simple.getId() + " (" + value.toString() + ")");
        } else if (descriptor instanceof ChildPropertyDescriptor) {
            ChildPropertyDescriptor child = (ChildPropertyDescriptor) descriptor;
            ASTNode childNode = (ASTNode) node.getStructuralProperty(child);
            if (childNode != null) {
                System.out.println("Child (" + child.getId() + ") {");
                print(childNode);
                System.out.println("}");
            }
        } else {
            ChildListPropertyDescriptor list = (ChildListPropertyDescriptor) descriptor;
            System.out.println("List (" + list.getId() + "){");
            print((List) node.getStructuralProperty(list));
            System.out.println("}");
        }
    }
}

private void print(List nodes) {
    for (Iterator iterator = nodes.iterator(); iterator.hasNext();) {
        print((ASTNode) iterator.next());
    }
}