A Starting a new temporary conversation<\/h3>\n\r\n@BeginTemporaryConversation(conversationName = ConversationEnum.C1)\r\npublic void doGetUserDetails(User user) {\r\n\t...\r\n\tUserDetails details = myDao.loadUserDetails(ConversationEnum.C1, user);\r\n\t...\r\n}\r\n<\/pre>\nIn the above code, to start a new temporary conversation, we simply need to annotate it with the @BeginTemporaryConversation<\/em><\/strong> annotation, providing the conversation name and indicating whether the conversation should start a transaction or not.<\/p>\nPlease notice in the example that we pass the ConversationEnum<\/strong> as the first parameter<\/strong> down to the DAO layer. This parameter is mandatory so the TemporaryConversationAnnotationProcessor<\/strong> knows that we’re currently in a temporary conversation context. The ConversationEnum<\/strong> is also necessary to get the name of the related Entity Manager Factory<\/strong> in Spring context and thus create the temporary Entity Manager<\/strong>.<\/p>\nB Accessing the temporary Entity Manager in DAO layer<\/h3>\n\r\npublic class MyDao {\r\n\t@PersistenceContext(unitName="myPersistenceUnit ")\r\n\tprivate EntityManager em;\r\n\r\n\tpublic UserDetails loadUserDetails(ConversationEnum conversation, User user) {\r\n\t\t...\r\n\t\tem.createQuery(query);\r\n\t\t...\r\n\t} \r\n }\r\n<\/pre>\nThe Entity Manager em<\/strong> in use in the method loadUserDetails()<\/strong> is injected by Spring. However, since the method loadUserDetails()<\/strong> is intercepted by the TemporaryConversationAnnotationProcessor<\/strong>, the injected Entity Manager<\/strong> is the one created for the temporary conversation.<\/p>\nC Ending a temporary conversation<\/h3>\n\r\n@EndTemporaryConversation(conversationName = ConversationEnum.C1)\r\n@Transactional(value = "myTransactionManager1", propagation = Propagation.REQUIRED) \r\npublic void doUpdateUserDetails(User user) \r\n{ \r\n\t...\r\n\t\/\/ Clear references\r\n\t...\r\n}\r\n<\/pre>\nTo end a conversation, we simply annotate the last method of the conversation with @EndTemporaryConversation<\/em><\/strong>. <\/p>\nPlease notice the use of Spring standard @Transactional annotation to create a JDBC transaction. Conversations and JDBC transactions are both cross-cuting concerns and completely uncorrelated.<\/p>\n
We should not forget to clean all references to entities that were loaded in the temporary Entity Manager and now become detached. These references should be removed in all beans, from Service to View layer if necessary. Forgetting to do so may result in the famous “Detached entities passed to persist\/delete<\/em>” Hibernate exception if these entities are re-used in another Entity Manager.<\/p><\/blockquote>\nD Cancelling a temporary conversation<\/h3>\n\r\n@TemporaryConversationEnd(conversationName = ConversationEnum.C1)\r\npublic void doCancelUserDetailsUpdate(User user) \r\n{ \r\n\t...\r\n\t\/\/ Clear references\r\n\t...\r\n}\r\n<\/pre>\nIt is also possible to rollback a temporary conversation by removing Spring @Transactional annotation. DML statements will not be committed to the database outside of a transactional context.<\/p>\n","protected":false},"excerpt":{"rendered":"
Today we discuss about temporary conversations in JPA, their usage, all usage warnings and a sample implementation using Spring AOP This article follows upon a previous one about global long conversation : JPA\/Hibernate Long session<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[20,7,16],"tags":[34,36,40],"_links":{"self":[{"href":"https:\/\/www.doanduyhai.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/593"}],"collection":[{"href":"https:\/\/www.doanduyhai.com\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.doanduyhai.com\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.doanduyhai.com\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.doanduyhai.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=593"}],"version-history":[{"count":3,"href":"https:\/\/www.doanduyhai.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/593\/revisions"}],"predecessor-version":[{"id":13536,"href":"https:\/\/www.doanduyhai.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/593\/revisions\/13536"}],"wp:attachment":[{"href":"https:\/\/www.doanduyhai.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=593"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.doanduyhai.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=593"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.doanduyhai.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=593"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
![\"\"](\"https:\/\/www.doanduyhai.com\/blog\/wp-content\/uploads\/2012\/01\/temp_conversation.png\" "\\"Temp_Conversation\\"")
<\/a>![\"\"](\"https:\/\/www.doanduyhai.com\/blog\/wp-content\/uploads\/2012\/02\/conversationmanager_temporaryconversationannotationprocessor.png\" "\\"ConversationManager_TemporaryConversationAnnotationProcessor\\"")
<\/a><\/p>\n![\"\"](\"https:\/\/www.doanduyhai.com\/blog\/wp-content\/uploads\/2012\/01\/temporaryconversationannotationprocessor.png\" "\\"TemporaryConversationAnnotationProcessor\\"")
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