SFSB provide thread syfety, lifecycle managment and can be used by different client types (not only web browsers). HTTP Sessions (Servlet in your question) can be easily programmed. SFSB can be used in clusters by replica aware stubs. There are app servers that also provide HTTP session clustering.
Use SFSB when 1) U need Transaction aware components 2) varied Client types 3) reusebility of business logic is an issue 4) if business process involves only single HTTP request and multiple beans are collabrating to fulfill request. And a been not recvng direct call from client needs to assess the client specific session data. Thanks Deepak Arora
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