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| <h1 class="topictitle1">Session Beans</h1> |
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| <div><p /> |
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| <p>A <strong>session bean</strong> is a type of enterprise bean. It is created by a |
| client and usually exists only for the duration of a single client-server |
| session.</p> |
| |
| <p>Session beans are useful for describing interactions between other beans |
| (taskflow) and for implementing particular tasks. They do not represent data |
| in the database, but they can access data, so we can use session beans to |
| read, update, and insert data in a business process. Session beans access |
| data that spans concepts, is not shared, and is usually read-only. Session |
| beans contain business logic, and entities model persistent data. There are |
| three types of session beans: stateless, stateful and singleton. </p> |
| |
| <ul> |
| <li><strong>Stateless session beans</strong> <p>A stateless session bean is pooled by |
| the container to handle multiple requests from multiple clients and does not |
| maintain any conversational state.</p> |
| </li> |
| |
| <li> <strong>Stateful session beans</strong> <p>A stateful session bean acts on behalf |
| of a single client and maintains client-specific session information (called |
| conversational state) across multiple method calls and transactions. It exists |
| for the duration of a single client/server session.</p> |
| </li> |
| |
| <li> <strong>Singleton session beans</strong> <p>A Singleton session bean is a session |
| bean component that is instantiated once per application. In cases where the container |
| is distributed over many virtual machines, each application will have one bean instance |
| of the Singleton for each JVM.</p> |
| </li> |
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| </ul> |
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| <div class="familylinks"> |
| <div class="parentlink"><strong>Parent topic:</strong> <a href="../topics/sessbwiz.html" title="You can use a wizard to create a session bean and add it to your project.">Creating EJB Session Beans</a></div> |
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