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Platforms
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Java |
- J2EE
- J2SE
- J2ME with reflection: CDC, PersonalProfile, Symbian, JavaFX Mobile and Zaurus; on
demand(2): J2ME w/o reflection (CLDC and MIDP), including RIM/Blackberry
and Palm OS.
- Android (Open
Handset Alliance)
- Harmony
- Supported Frameworks: Spring, OSGi, Tomcat, JPOX
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.NET |
- .NET Framework (1.0(1), 2.0, 3.0, 3.5)
- .NET Compact Framework 1.0(1), 2.0
- Windows (XP, Vista)
- Windows Mobile / PocketPC
- Mono(1)
- Supported Frameworks: Castle, Eiffel, Spring.net
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Cross-platform |
- Connect to .NET server with Java client
- Connect to Java server with .NET client
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Languages
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Java |
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.NET |
- All managed .NET languages
(C#, VB.NET, ASP.NET, Boo, Managed C++ etc.)
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Commands
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Sessions |
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Database files |
- Create, open, close, and delete
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Transactions |
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Objects |
- Store, retrieve, update (incl. cascaded), replicate, delete (incl. cascaded)
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Messaging |
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Transparency
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Language constructs |
- Primitive types
- Strings
- Arrays
- Multi-dimensional arrays
- Inner classes
- Java/C# collections
- Classes without public constructors
- .NET structs
- Blobs (stored outside of DB file)
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Non-Intrusive |
- Without deriving from a specific base class
- Without implementing a specific interface
- Without modifications to source code
- Without implementing Serializable
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Private Fields |
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File I/O |
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Reflector |
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Aliases |
- Class aliasing for class-to-class mappings
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Query Languages / APIs
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Object oriented |
- Native Queries (NQ)
- Query By Example (QbE)
- S.O.D.A.
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SQL |
- Via replication to many relational databases
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XML |
- With Third-Party products (e.g.,
Xstream)
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Modes / Concurrency
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Operation Modes |
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Threads |
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Transactions |
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Semaphores |
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Read-Only Mode |
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Scalability and Performance
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Performance benchmark |
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Examples of Scalability |
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In Memory Mode |
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Client-side |
- Single-process execution available
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Server-side |
- Server-side query execution available
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DB-aware Collections |
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Object Caching |
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Pagination |
- Server-side cursors (lazy queries)
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Indexing |
- BTree field indexes
- BTree query processor
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Replication
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db4o Replication System (dRS) |
- 100% object-oriented: simply replicate objects, not tables
- Uni- and bi-directional
- db4o to db4o
- db4o to relational databases (RDBMS), wrapped in Hibernate (Java only)
- Hibernate/RDBMS to Hibernate/RDBMS (Java only)
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UUID |
- Unique Universal Identity over all DB instances
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Synchronization |
- Querying
- Update
- Delete
- Conflict resolution
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Reporting
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For Java objects |
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For .NET objects |
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Security and Encryption
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DB file Protection |
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DB file Encryption |
- Simple database encryption
- Pluggable File I/O for custom encryption
- With Third-Party products (e.g.,
XTEA)
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Availability, Reliability, Zero-Admin
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Transactions |
- ACID
- Commit-recovery on system failures
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Thread Safety |
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Automatic Recovery |
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Online-Backup |
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Free Space Management |
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Internationalization
Refactoring
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Schema Versioning |
- Automatic recognition and maintenance
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Schema Merge |
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Renaming |
- Classes, fields by API
- Access to values of removed fields by API or with ObjectManager UI
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Memory and file size
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DB library footprint |
- <1 MB
- Small footprint (~600k) available on demand(2)
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Minimal RAM footprint |
- Application dependent; deterministic; below 3 MB for all but one PolePosition benchmark
(www.polepos.org)
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Maximum DB file size |
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Class size |
- No increase when persisted
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Instance size |
- No increase when persisted
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(1) available through 3rd party providers or db4o developer community projects
(2) available on demand, built to order against services contract
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