Find which class an object was instantiated in

Question

I am trying to learn unnecessarily complicated source code. There is a method public void passObject(SomeObject someObject), and I want to know which class someObject was instantiated in. The problem is, as we traverse up the call hierarchy, the branching factor is very large. For example, three methods can pass someObject through passObject, and three methods before these three methods can pass the same object respectively.

Is there some method that I can insert into passObject such as:

public void passObject(SomeObject someObject) {
    whereDidThisComeFrom(someObject); // Should print the class (perhaps) where someObject was instantiated.
    //
    //do the other stuff that passObject is supposed to do.
}

I use Eclipse.

I dont know if it is the same or not but check this thread: http://stackoverflow.com/questions/421280/how-do-i-find-the-caller-of-a-method-using-stacktrace-or-reflection — Raul Guiu, Mar 21 '14 at 09:07

score 3 · Accepted Answer · answered Mar 21 '14 at 09:19

3

The easiest / dirtiest way is to just put (new Exception("test")).printStackTrace() in SomeObject's constructor and run the code. You'll get a stack trace printed to the console every time SomeObject is instantiated.

Eclipse also supports breakpoints in constructors so you could set a breakpoint and debug.

answered Mar 21 '14 at 09:19

lance-java

25,497
4
59
101

You can get a stack trace without creating an exception. See the link in my answer – NickJ Mar 21 '14 at 09:21
I didn't say it was great code, I said it was easy. – lance-java Mar 21 '14 at 09:23
The is really good and has solved my problem. Who cares if it's a bit dirty, it works brilliantly. – user2763361 Mar 21 '14 at 09:30

score 2 · Answer 2 · edited May 23 '17 at 12:19

It's true that using 'Show Call Hierachy' can show too many results to really give you an idea of execution flow.

Instead, you could try using Eclipse in debug mode, and put a break-point on the first line of passObject(SomeObject someObject). You'll then see the current stack-trace. By inspecting the code on the stack-trace you can determine the call hierarchy which actually occurred.

Alternatively, if you can't debug, can you add another line to passObject(SomeObject someObject) to print the current stack trace? See here for details.

Find which class an object was instantiated in

2 Answers2