How to read schema-less documents using Java from MongoDB

Question

MongoDB gives the ability to write documents of any structure i.e. any number and types of key/value pairs can be written. Assuming that I use this features that my documents are indeed schema-less then how do I manage reads, basically how does the application code ( I'm using Java ) manage reads from the database.

Answer 1

The java driver reads and writes documents as BasicBSONObjects, which implement and are used as Map<String, Object>. Your application code is then responsible for reading this map and casting the values to the appropriate types.

A mapping framework like Morphia or Spring MongoDB can help you to convert BSONObject to your classes and vice versa.

When you want to do this yourself, you could use a Factory method which takes a BasicBSONObject, checks which keys and values it has, uses this information to create an object of the appropriate class and returns it.