Using the EJB 1.1 specifications, container managed persistence beans were not very powerful. In most cases, bean developers went quickly beyond the capabilities of CMP and had to convert to use bean managed persistence. Many developers shied away from using entity beans altogether. The EJB 2.0 quickly addressed many of these issues. This now allows the bean developer to implement most persistence requirements using container managed persistence. The four features that facilitate this are the following:
EJB query language
Relationship mapping of multiple entity beans
Business methods implemented within the home interface
The Enterprise JavaBeans Query ...