Pretty-print object hierarchy in Java?

Question

I'm working on a data analytics project where we are representing a lot of the basic entities you find in a language. I'd like to find a better way to print out their object graphs though for debugging purposes though. So, for example, we might have:

Function: Average
Description: some description
Overload #1:
    parameter-set: paramset-a
        columns: 
           currency: string
           value: double
           scale: integer
    result-set: result-set-a
    preference: first-find
Overload #2: ...
Overload #3: ...

My Question

Let's say, in the above example, Function is my root object. Function has some attributes and a series of overloads, each with their own attributes and child objects.

Is there a library that can help me to print the object graph under a root function, in a well-formatted way?

PS: The above example is relatively trivial; in many of our cases, the object hierarchies are 6-10 levels deep, and that's when the real problem comes in.

Do the objects have attributes, some of which have child nodes you have to recurse into? When I've had to format data like this a simple recursive enumeration that has an indentation parameter that gets incremented at each level of recursion has always come in handy. — David Conrad, Apr 07 '14 at 18:15
Yeah, they have attributes. I was thinking along the same lines as you... Maybe like a "toString(int tabs)" function that I can call for each entity, and I just return the tabs + the normal toString() for the entity. I was kinda hoping there's a library that prints out the attributes of each class though to avoid the extra code. — John Humphreys, Apr 07 '14 at 19:35
Well, I don't know of one. Maybe someone else will reply with one. — David Conrad, Apr 07 '14 at 20:03

score 1 · Accepted Answer · answered Jan 30 '20 at 09:16

This is far from perfect, but this question really deserves an answer.

https://github.com/EsotericSoftware/jsonbeans is one way to kind of accomplish something like this. It converts arbitrary Java objects (without having to annotate the fields or anything) to JSON, and includes a pretty-printing method. It can do approximately what you are asking for.

Using this library, you can do something like this:

Json json = new Json();
System.out.println(json.prettyPrint(person));

For some example data, the output you might get looks like this:

{
"name": "Nate",
"age": 31,
"numbers": [
   {
      "name": "Home",
      "class": "com.example.PhoneNumber",
      "number": "206-555-1234"
   },
   {
      "name": "Work",
      "class": "com.example.PhoneNumber",
      "number": "425-555-4321"
   }
]
}

Pretty-print object hierarchy in Java?

1 Answers1