2. Nested and recursive objects
JSX can create an instant file format for your data, which you can then configure manually with a plain text editor. Manually coding such a format is a lot of tedious work - and you also have to write the parsing code. This coding is especially unpleasant when your objects have a nested or recursive structure. Java Object serialization (JOS) also works well for this task, except that you cannot see or edit the resulting binary. JOS also requires objects to implement the Serializable interface, and so won't work with all objects. JSX does not have this restriction, and works for objects whether they implement Serializable or not. Here is a case study.

3. Human readable
XML is easy to check and verify; and automatic serialization eliminates human error in the mapping code. JSX is an instant solution, and removes the error-prone tedium of writing and mantaining externalization code by hand.