Spring boot 为什么SpringDataJPA为共享EntityManager调用创建新的EntityManager？

我有一个使用SpringBoot+SpringDataJPA的示例项目。在日志中，我观察到EntityManager在我进行第一次rest调用之前被创建了几次。请澄清为什么会发生这种情况。多谢

Initialized JPA EntityManagerFactory for persistence unit 'ENTITY_MGR'
SpringBoot --> 10:05:40 8766 DEBUG org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler [main] - Creating new EntityManager for shared EntityManager invocation
SpringBoot --> 10:05:41 8963 DEBUG org.hibernate.stat.internal.StatisticsInitiator [main] - Statistics initialized [enabled=true]
SpringBoot --> 10:05:41 8977 TRACE org.hibernate.internal.SessionImpl [main] - Opened Session [f35fe4ac-8ce1-46b8-90dc-e456c07015c9] at timestamp: 15339099411
SpringBoot --> 10:05:41 8980 DEBUG org.springframework.orm.jpa.EntityManagerFactoryUtils [main] - Closing JPA EntityManager
SpringBoot --> 10:05:41 8982 TRACE org.hibernate.internal.SessionImpl [main] - Closing session [f35fe4ac-8ce1-46b8-90dc-e456c07015c9]
SpringBoot --> 10:05:41 8982 INFO  org.hibernate.engine.internal.StatisticalLoggingSessionEventListener [main] - 
SpringBoot --> 10:05:41 8983 TRACE org.hibernate.resource.jdbc.internal.ResourceRegistryStandardImpl [main] - Releasing JDBC resources
SpringBoot --> 10:05:41 8983 TRACE org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl [main] - Closing logical connection
SpringBoot --> 10:05:41 8983 TRACE org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl [main] - Logical connection closed
SpringBoot --> 10:05:41 8985 DEBUG org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler [main] - Creating new EntityManager for shared EntityManager invocation
SpringBoot --> 10:05:41 8986 TRACE org.hibernate.internal.SessionImpl [main] - Opened Session [26018255-8491-4014-98ad-fbce0d3b5109] at timestamp: 15339099412
SpringBoot --> 10:05:41 8986 DEBUG org.springframework.orm.jpa.EntityManagerFactoryUtils [main] - Closing JPA EntityManager
SpringBoot --> 10:05:41 8986 TRACE org.hibernate.internal.SessionImpl [main] - Closing session [26018255-8491-4014-98ad-fbce0d3b5109]
SpringBoot --> 10:05:41 8986 INFO  org.hibernate.engine.internal.StatisticalLoggingSessionEventListener [main] - 
SpringBoot --> 10:05:41 8986 TRACE org.hibernate.resource.jdbc.internal.ResourceRegistryStandardImpl [main] - Releasing JDBC resources
SpringBoot --> 10:05:41 8986 TRACE org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl [main] - Closing logical connection
SpringBoot --> 10:05:41 8986 TRACE org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl [main] - Logical connection closed
SpringBoot --> 10:05:41 9069 DEBUG org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler [main] - Creating new EntityManager for shared EntityManager invocation
SpringBoot --> 10:05:41 9069 TRACE org.hibernate.internal.SessionImpl [main] - Opened Session [4d3e7b5f-46fe-436f-9526-7ba62e332846] at timestamp: 15339099412
SpringBoot --> 10:05:41 9069 DEBUG org.springframework.orm.jpa.EntityManagerFactoryUtils [main] - Closing JPA EntityManager
SpringBoot --> 10:05:41 9069 TRACE org.hibernate.internal.SessionImpl [main] - Closing session [4d3e7b5f-46fe-436f-9526-7ba62e332846]
SpringBoot --> 10:05:41 9069 INFO  org.hibernate.engine.internal.StatisticalLoggingSessionEventListener [main] - 
SpringBoot --> 10:05:41 9070 TRACE org.hibernate.resource.jdbc.internal.ResourceRegistryStandardImpl [main] - Releasing JDBC resources
SpringBoot --> 10:05:41 9070 TRACE org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl [main] - Closing logical connection
SpringBoot --> 10:05:41 9070 TRACE org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl [main] - Logical connection closed
SpringBoot --> 10:05:41 9248 DEBUG org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler [main] - Creating new EntityManager for shared EntityManager invocation
SpringBoot --> 10:05:41 9248 TRACE org.hibernate.internal.SessionImpl [main] - Opened Session [1b5f5936-fa7f-42cd-831c-78570ace0f58] at timestamp: 15339099414
SpringBoot --> 10:05:41 9248 DEBUG org.springframework.orm.jpa.EntityManagerFactoryUtils [main] - Closing JPA EntityManager
SpringBoot --> 10:05:41 9248 TRACE org.hibernate.internal.SessionImpl [main] - Closing session [1b5f5936-fa7f-42cd-831c-78570ace0f58]
SpringBoot --> 10:05:41 9249 INFO  org.hibernate.engine.internal.StatisticalLoggingSessionEventListener [main] - 
SpringBoot --> 10:05:41 9249 TRACE org.hibernate.resource.jdbc.internal.ResourceRegistryStandardImpl [main] - Releasing JDBC resources
SpringBoot --> 10:05:41 9249 TRACE org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl [main] - Closing logical connection
SpringBoot --> 10:05:41 9249 TRACE org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl [main] - Logical connection closed

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我有70行这样的文章。。。。永远得不到答案