Extract methods calls from java code

Question

I want to extract all method calls from java code. I have written following two regular expression but they are not able to extract all the method calls.

Reg1 : Pattern.compile("([a-zA-Z][0-9_a-zA-Z]*\\([a-zA-Z0-9_\\s,\\[\\]\\(\\)\\.]+\\))");

Reg2 : Pattern.compile("([a-zA-Z][0-9_a-zA-Z]*\\([\\s]*\\))")

Input:

"{
     if ((war == null) && (config != null)) {
    sb.append( &config= );
    sb.append(URLEncoder.encode(config,getCharset()));
    }
    if ((war == null) && (localWar != null)) {
    sb.append( &war= );
    sb.append(URLEncoder.encode(localWar,getCharset()));
    }
    if (update) {
    sb.append( &update=true );
    }
    if (tag != null) {
      sb.append( &tag= );
      sb.append(URLEncoder.encode(tag,getCharset()));
     }
     }"

output:

getCharset getCharset getCharset append append append

I am not able to extract "encode".

Does anyone have any idea as an what should I add to regular expression?

This is (according to well-established principles of language theory) impossible to do using regular expressions, mainly because each call may contain calls that may contain calls that ... — laune
– laune, Commented Sep 17, 2015 at 5:02
Perhaps this post is of any help stackoverflow.com/questions/2206065/… — Mariano
– Mariano, Commented Sep 17, 2015 at 5:19
Thanks! but I want to extract method calls made in the program. — Sangeeta
– Sangeeta, Commented Sep 17, 2015 at 5:24

Koray Tugay · Accepted Answer · 2019-06-06 15:37:41Z

10

You need a Java Code Parser for this task. Here is an example which uses Java Parser:

public class MethodCallPrinter
{
    public static void main(String[] args) throws Exception
    {
        FileInputStream in = new FileInputStream("MethodCallPrinter.java");

        CompilationUnit cu;
        try
        {
            cu = JavaParser.parse(in);
        }
        finally
        {
            in.close();
        }
        new MethodVisitor().visit(cu, null);
    }

    private static class MethodVisitor extends VoidVisitorAdapter
    {
        @Override
        public void visit(MethodCallExpr methodCall, Object arg)
        {
            System.out.print("Method call: " + methodCall.getName() + "\n");
            List<Expression> args = methodCall.getArgs();
            if (args != null)
                handleExpressions(args);
        }

        private void handleExpressions(List<Expression> expressions)
        {
            for (Expression expr : expressions)
            {
                if (expr instanceof MethodCallExpr)
                    visit((MethodCallExpr) expr, null);
                else if (expr instanceof BinaryExpr)
                {
                    BinaryExpr binExpr = (BinaryExpr)expr;
                    handleExpressions(Arrays.asList(binExpr.getLeft(), binExpr.getRight()));
                }
            }
        }
    }
}

Output:

Method call: parse
Method call: close
Method call: visit
Method call: print
Method call: getName
Method call: getArgs
Method call: handleExpressions
Method call: visit
Method call: handleExpressions
Method call: asList
Method call: getLeft
Method call: getRight

edited Jun 6, 2019 at 15:37

Koray Tugay

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answered Sep 17, 2015 at 7:03

splash

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9 Comments

laune Over a year ago

The main difficulty is to handle recursions in the sentences. You might add this to your answer, e.g., another visitor for expressions.

splash Over a year ago

@laune what do you mean with "recursions in the sentences"?

laune Over a year ago

The Java grammar defines how "sentences" of the language are to be constructed. In the definition of "method call", via some NTs in between, "method call" appears again: recursion. - So there must be an iteration for( Expression e: methodCall.getArgs() ){ ... } etc.

splash Over a year ago

@laune Understand. I overlooked that. Thought that Java Parser would handle this gracefully. :-)

splash Over a year ago

@Sangeeta you could use methodCall.getBeginLine() to check if the method call is inside of your desired part of the source code.

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