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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) |
| Life Cycle | |
| Objects live until transaction completes | Objects can live as long as PersistenceManager (more) |
| 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) |
| 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:
- Transparent persistence for object databases (new window)
- Transparent persistence for relational databases using object-relational mapping products (new window)
For more information on ODMG 3.0 and JDO as well as other database specifications, see the related content below.
More on the general topic: DBMS standards
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