How to get corresponding Byte code of java MethodDeclaration

Question

I want to get the byte code for a java method signature given MethodDeclaration object. I'm parsing the java class using Eclipse jdt and iterating over the MethodDeclaration like the following:

private static void processJavaFile(String javaFilePath) {
    List<MethodDeclaration> methodDeclarations = new ArrayList<MethodDeclaration>();
    FileInputStream reader = null;
    try {
        File javaFile = new File(javaFilePath);
        reader = new FileInputStream(javaFile);

        byte[] bs = new byte[reader.available()];
        reader.read(bs, 0, reader.available());
        String javaContent = new String(bs);

        CompilationUnit unit = ASTUtil.getCompilationUnit(javaContent, 4);
        MethodVisitor methodVisitor = new MethodVisitor();
        unit.accept(methodVisitor);
        methodDeclarations = methodVisitor.getMethods();
        for (MethodDeclaration methodDeclaration :methodDeclarations){
            ////////////////////////////////////////////////////////////////////////
            // ???? I want to get the byte code of the method signature here ???? //
            ////////////////////////////////////////////////////////////////////////
        }
    } catch (Exception e) {
        e.printStackTrace();
    }

} 

Answer 1

The MethodDeclaration instance is part of the AST representing the syntax of the source code. It requires resolving the type names found in the source code before you can create a signature for a method.

for (MethodDeclaration methodDeclaration :methodDeclarations){
  // the next line requires that the project is setup correctly
  IMethodBinding resolved = methodDeclaration.resolveBinding();
  // then you can create a method signature
  ITypeBinding[] pType = resolved.getParameterTypes();
  String[] pTypeName=new String[pType.length];
  for(int ix = 0; ix < pType.length; ix++)
    pTypeName[ix]=pType[ix].getBinaryName().replace('.', '/');
  String rTypeName=resolved.getReturnType().getBinaryName().replace('.', '/');
  //org.eclipse.jdt.core.Signature
  String signature = Signature.createMethodSignature(pTypeName, rTypeName);
  System.out.println(signature);
}