Detailed Comparison of ODMG 3.0 and JDO

This table shows a summary of the similarities and differences between the two approaches to transparent persistence: ODMG 3.0 and JDO. It is from a presentation at JavaOne by Heiko Bobzin of POET Software.

ODMG 3.0 JDO
Object Model
Transparent Persistence Transparent Persistence
Persistence by Reachability Persistence by Reachability
Java, C++, and Smalltalk Language Bindings on top of ODMG object model Tight integration with Java object model
Vendor specific interfaces PersistenceCapable interface
Collection factory for five basic collections Collection factory “by Example”, Second Class Objects
Object identity managed by database system Three identity models (more on identiy models)
Life Cycle
Objects live until transaction completes Objects can live as long as PersistenceManager (more on persistence manager)
Objects can not be accessed after transaction completes API allows the setting of properties
Callbacks not defined Callbacks for load, store, delete, and clear
Databases and Transactions
Easy to use but proprietary database and transaction management Databases, connections and transactions fit into other Java APIs
No distributed transactions defined Support for distributed transactions
Vendor specific extensions for managed environments (EJB) Support for managed environments (EJB)
Vendor specific extension for optimistic locking Optimistic locking is optional API
Explicit locking of objects No explicit locking -- locks set automatically
Query
OQL: an extensive object query language Queries based on Java programming language — JDOQL (more on JDOQL)
Complex query expressions Simple filter strings
Results can be compositions, projections or just an integer Results are always collections of persistence capable objects
Class name is part of query string Class objects explicitly used as parameters
No imports or name scope Imports, "this", named parameters

This table, copyright ? 2001 FastObjects by Poet, used with permission.

For more information on transparent persistence, see:

For more information on ODMG 3.0 and JDO as well as other database specifications, see the related content below.

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