OpenEJB是一个嵌入式，轻量级EJB3.0实现。既可以作为单独服务器使用，也可以嵌入到Tomcat、JUnit、Eclipse、 Intellij、Maven、Ant和其它任何IDE与应用程序中。OpenEJB 被用于Apple的WebObjects与Apache的Geronimo应用服务器中。

3.1 版本部分实现 EJB 3.1 ，包括完全支持 EJB 3.1 中的 Singleton Session bean ，主要的改进包括如下一些个方面：

EJB 3.1 features and EJB enhancements:

• Singleton Session Beans
• Constructor Injection
• Spring Integration

Tomcat features:

• Injection Support for JSF 1.2 ManagedBeans

Embedded features:

• EAR-style aggregation of modules discovered in the classpath
• ConnectorModule discoverable via the classpath (rar files)
• PersistenceModule discoverable via the classpath
• Improved JavaAgent/JPA enhancement for Unit Tests
• Improved detection of testing and embedded scenarios
• Improved classpath configuration searching
• Property overriding for logging configuration
• Property overriding for persistence.xml properties
• VM-scoped Security for embedded scenarios
• LocalInitialContext.close() to logout of embedded container
• LocalInitialContext.close() to shutdown embedded container
• JMS runs port-free in embedded mode
• Automatically set eclipselink.target-server for EclipseLink
• Automatically set toplink.target-server for TopLink
• Automatically set hibernate.transaction.manager_lookup_class for Hibernate
• Optimized annotation scanner to determine if a jar is an ejb jar more quickly

Standalone features:

• Severely improved client performance over ejbd
• Client Connection Failover and Request Retry
• Client-side Connection Pool
• Client connection KeepAlive
• Graceful shutdown of client/server connections
• Multicast discovery and grouping
• EJBd protocol over SSL
• JDBC/DataSource based login module