Prior knowledge or experience in database programming (SQL, JDBC, ORM, JPA, etc.) is not required, but some background in using the Java language is essential.
What is the Java Data Objects (JDO)?
The Java Data Objects (JDO) is another standard for accessing persistent data in databases, using plain old Java objects (POJO) to represent the object model. Unlike Java Persistence API (JPA), which is designated to be used with relational databases, JDO is designated to be used with both relational and object databases. JDO is supported by many object databases, including ObjectDB, and it is probably the most popular Java API for object databases today.