How to Resolve Bindings When Using Eclipse JDT ASTParser?

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When using ASTParser, we often need to find type of variable in the code. This information is contains in the binding. The following code shows how to write a stand alone ASTParser to parse Java file and get the type information of variables in the code.

The target code to parse:

package test;
 
import java.util.ArrayList;
 
public class Apple {
	public static void main(String[] args) {
		ArrayList<String> al = null;
		int j =0;
		System.out.println(j);
		System.out.println(al);
	}
}

Resolve bindings using Eclipse JDT ASTParser:

package test;
 
import greenblocks.util.Util;
import java.io.File;
import java.util.Iterator;
import java.util.Map;
 
import org.eclipse.jdt.core.JavaCore;
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.IVariableBinding;
import org.eclipse.jdt.core.dom.VariableDeclarationFragment;
import org.eclipse.jdt.core.dom.VariableDeclarationStatement;
 
public class ASTTester {
 
	public static void main(String[] args) {
		String path ="C:\\Users\\pc\\workspace\\asttester\\src\\test\\Apple.java";
		File file = new File(path);
		String str = Util.readFileToString(file);
 
		ASTParser parser = ASTParser.newParser(AST.JLS8);
		parser.setResolveBindings(true);
		parser.setKind(ASTParser.K_COMPILATION_UNIT);
 
		parser.setBindingsRecovery(true);
 
		Map options = JavaCore.getOptions();
		parser.setCompilerOptions(options);
 
		String unitName = "Apple.java";
		parser.setUnitName(unitName);
 
		String[] sources = { "C:\\Users\\pc\\workspace\\asttester\\src" }; 
		String[] classpath = {"C:\\Program Files\\Java\\jre1.8.0_25\\lib\\rt.jar"};
 
		parser.setEnvironment(classpath, sources, new String[] { "UTF-8"}, true);
		parser.setSource(str.toCharArray());
 
		CompilationUnit cu = (CompilationUnit) parser.createAST(null);
 
		if (cu.getAST().hasBindingsRecovery()) {
			System.out.println("Binding activated.");
		}
 
		TypeFinderVisitor v = new TypeFinderVisitor();
		cu.accept(v);		
	}
}
 
class TypeFinderVisitor extends ASTVisitor{
 
	public boolean visit(VariableDeclarationStatement node){
		for (Iterator iter = node.fragments().iterator(); iter.hasNext();) {
			System.out.println("------------------");
 
			VariableDeclarationFragment fragment = (VariableDeclarationFragment) iter.next();
			IVariableBinding binding = fragment.resolveBinding();
 
			System.out.println("binding variable declaration: " +binding.getVariableDeclaration());
			System.out.println("binding: " +binding);
		}
		return true;
	}
}

Output:

Binding activated.
------------------
binding variable declaration: ArrayList al[pos: unused][id:1]
binding: ArrayList al[pos: unused][id:1]
------------------
binding variable declaration: int j[pos: unused][id:2]
binding: int j[pos: unused][id:2]

4 thoughts on “How to Resolve Bindings When Using Eclipse JDT ASTParser?”

  1. hi i try you code and i have error


    /*
    * To change this license header, choose License Headers in Project Properties.
    * To change this template file, choose Tools | Templates
    * and open the template in the editor.
    */
    package testfile;
    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.AnonymousClassDeclaration;
    import org.eclipse.jdt.core.dom.Block;
    import org.eclipse.jdt.core.dom.CompilationUnit;
    import org.eclipse.jdt.core.dom.Expression;
    import org.eclipse.jdt.core.dom.IMethodBinding;
    import org.eclipse.jdt.core.dom.ITypeBinding;
    import org.eclipse.jdt.core.dom.MethodDeclaration;
    import org.eclipse.jdt.core.dom.MethodInvocation;
    /**
    *
    * @author ahmed
    */
    public class Test {

    String str = "package javaproject;" // package for all classes
    + "class Dummy {" //
    + " void testSearch(String queryStr, String dateStr, SearchResources twitter1) {" //
    + " Quer query = new Quer(queryStr).unti(dateStr);" //
    + " QueryResult queryResult = twitter1.search(query);"
    //
    + " int x=1;"
    + " File file=new File();"
    + "file.x();"
    + " int y;"
    + "public class TestThread {n" +
    " public static void main(String args[]) {n" +
    " n" +
    " RunnableDemo R1 = new RunnableDemo( "Thread-1");n" +
    " R1.start();n" +
    " n" +
    " RunnableDemo R2 = new RunnableDemo( "Thread-2");n" +
    " R2.start();n" +
    " } n" +
    "}"

    + " }" //
    + "}";

    public void testrun() {
    ASTParser parser = ASTParser.newParser(AST.JLS3);
    parser.setSource(str.toCharArray());
    parser.setKind(ASTParser.K_COMPILATION_UNIT);
    parser.setResolveBindings(true);

    // parser.setEnvironment( // apply classpath
    // new String[] { "C:\eclipse\workspace\JavaProject\bin" }, //
    // null, null, true);
    parser.setUnitName("any_name");

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

    cu.accept(new ASTVisitor() {

    public boolean visit(Expression anonyomousClassDeclaration) {

    System.out.println("next " + anonyomousClassDeclaration.toString());

    return true;
    }

    public boolean visit(MethodDeclaration node) {
    if (node.getName().getIdentifier().equals("testSearch")) {
    Block block = node.getBody();
    block.accept(new ASTVisitor() {
    public boolean visit(MethodInvocation node) {
    System.out.println("Name: " + node.getName());

    Expression expression = node.getExpression();
    if (expression != null) {
    System.out.println("Expr: " + expression.toString());

    ITypeBinding typeBinding = expression.resolveTypeBinding();
    if (typeBinding != null) {
    System.out.println("Type: " + typeBinding.getName());
    }
    }
    IMethodBinding binding = node.resolveMethodBinding();
    if (binding != null) {
    ITypeBinding type = binding.getDeclaringClass();
    if (type != null) {
    System.out.println("Decl: " + type.getName());
    }
    }

    return true;
    }
    });
    }
    return true;
    }
    });
    }
    }

    and i have problem in :
    Exception in thread “main” java.lang.NullPointerException
    at testfile.TypeFinderVisitor.visit(ASTTester.java:80)
    at org.eclipse.jdt.core.dom.VariableDeclarationStatement.accept0(VariableDeclarationStatement.java:266)
    in this line :
    System.out.println(“binding variable declaration: ” +binding.getVariableDeclaration());

    binding is null

  3. It turns out the problem is because I haven’t set up :

    String unitName = "Code.java";
    parser.setUnitName(unitName);

  4. Hi,

    I’ve tried to this binding tutorial, but unfortunately when I run this code, I got a NullPointerException at fragment.resolveBinding();
    So, do you have any idea on why could this happen?
    What probably did I do wrong?

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