"Key-Value Coding" for Java

Question

In Objective-C on Apple there is something called "Key-Value Coding" that allows you to traverse the object graph using strings similar to filesystem paths. There's an informal protocol (i.e. interface) that allows objects to return values based on the "key" they're asked for. e.g. The default is to return the value of a field named by the key, while relational collections like NSDictionaries can implement more interesting behavior.

Pseudo code example:

foo.bar = new baz();
foo.bar.mymap = new map();
foo.bar.mymap['bom'] = 2;

foo.valueForKeyPath("bar.mymap.bom") # 2

Is there anything like this for Java? It would be easy enough to implement, but I thought I'd look first.

Answer 1

PropertyUtils.getProperty, from apache's beanutils library, does this for JavaBean properties.

Answer 2

Hmm, well, in case anyone else has this question, it looks like MVEL is a good bet:

http://mvel.codehaus.org/Property+Navigation

Answer 3

The Ujorm is an open source Java library providing objects based on the key‑value architecture, see the examples.