Java introspection: object to map

Question

I have a Java object obj that has attributes obj.attr1, obj.attr2 etc. The attributes are possibly accessed through an extra level of indirection: obj.getAttr1(), obj.getAttr2(), if not public.

The challenge: I want a function that takes an object, and returns a Map<String, Object>, where the keys are strings "attr1", "attr2" etc. and values are the corresponding objects obj.attr1, obj.attr2. I imagine the function would be invoked with something like

• toMap(obj),
• or toMap(obj, "attr1", "attr3") (where attr1 and attr3 are a subset of obj's attributes),
• or perhaps toMap(obj, "getAttr1", "getAttr3") if necessary.

I don't know much about Java's introspection: how do you do that in Java?

Right now, I have a specialized toMap() implementation for each object type that I care about, and it's too much boilerplate.

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NOTE: for those who know Python, I want something like obj.__dict__. Or dict((attr, obj.__getattribute__(attr)) for attr in attr_list) for the subset variant.

Answer 1

Another way to user JacksonObjectMapper is the convertValue ex:

 ObjectMapper m = new ObjectMapper();
 Map<String,Object> mappedObject = m..convertValue(myObject, new TypeReference<Map<String, String>>() {});