Flow scope gets allocated when a flow starts and destroyed when the flow ends. With the default implementation, any objects stored in flow scope need to be serializable.spring-doc.cn

View scope gets allocated when a view-state enters and destroyed when the state exits. View scope is referenceable only from within a view-state. With the default implementation, any objects stored in view scope need to be serializable.spring-doc.cn

Request scope gets allocated when a flow is called and destroyed when the flow returns.spring-doc.cn

Flash scope gets allocated when a flow starts, cleared after every view render, and destroyed when the flow ends. With the default implementation, any objects stored in flash scope need to be serializable.spring-doc.cn

Conversation scope gets allocated when a top-level flow starts and gets destroyed when the top-level flow ends. Conversation scope is shared by a top-level flow and all of its sub-flows. With the default implementation, conversation-scoped objects are stored in the HTTP session and should generally be serializable to account for typical session replication.spring-doc.cn

The scope to use is often determined contextually — for example, depending on where a variable is defined: at the start of the flow definition (flow scope), inside a a view state (view scope), and so on. In other cases (for example, in EL expressions and Java code), you must specify it explicitly. Subsequent sections explain how this is done.spring-doc.cn