docs/org.eclipse.jst.ejb.doc.user/topics/sessbwiz.dita

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<task id="sessbwiz" xml:lang="en-us">
<title>Creating EJB Session Beans</title>
<shortdesc>You can use a wizard to create a session bean and add it
to your project.</shortdesc>
<prolog><metadata>
<keywords><indexterm>session beans</indexterm><indexterm>creating</indexterm>
</keywords>
</metadata></prolog>
<taskbody>
<context><p>The session bean wizard helps you create an Enterprise
session bean by walking you through the creation process and by providing
you with output files that you can use or that you can modify for
use with your application.</p> <p>To create a session bean, complete
the following steps:</p></context>
<steps>
<step><cmd>From the <tm tmclass="special"
tmowner="Sun Microsystems, Inc." tmtype="tm" trademark="Java">Java</tm> EE
perspective, expand your  EJB project in the Project Explorer view.</cmd>
</step>
<step><cmd>Right click on the <b>Session Bean</b> icon, and select <menucascade>
<uicontrol>New</uicontrol><uicontrol>Session Bean</uicontrol>
</menucascade> from the pop-up menu.</cmd><stepresult> The <uicontrol>Create
Session Bean</uicontrol> wizard appears.</stepresult></step>
<step><cmd>Follow the project wizard prompts.</cmd></step>
</steps>
<postreq><p><b>General Information</b></p><dl><dlentry>
<dt>State type</dt>
<dd>There are three types of session beans: stateless, stateful and
singleton. <dl><dlentry>
<dt>Stateless session beans</dt>
<dd>A stateless session bean is a collection of related services,
each represented by a method; the bean maintains no state from one
method invocation to the next. When you invoke a method on a stateless
session bean, it executes the method and returns the result without
knowing or caring what other requests have gone before or might follow.
Stateless session beans have longer lives because they do not maintain
any conversational state.</dd>
</dlentry><dlentry>
<dt>Stateful session beans</dt>
<dd>A stateful session bean performs tasks on behalf of a client and
maintains state related to that client. This state is called conversational
state because it represents a continuing conversation between the
stateful session bean and the client. Methods invoked on a stateful
session bean can write and read data to and from this conversational
state, which is shared among all methods in the bean. Stateful session
beans have timeout periods.</dd>
</dlentry><dlentry>
<dt>Singleton session beans</dt>
<dd>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.  Once instantiated, a Singleton session
bean instance lives for the duration of the  application in which
it is created. It maintains its state between client invocations 
but that state is not required to survive container shutdown or crash.
A Singleton  session bean is intended to be shared and supports concurrent
access.</dd>
</dlentry></dl></dd>
</dlentry></dl> <dl><dlentry>
<dt>Business interface</dt>
<dd>A business interface of a session bean is an ordinary <tm
tmclass="special" tmowner="Sun Microsystems, Inc." tmtype="tm"
trademark="Java">Java</tm> interface that contains the business methods
for the bean. A reference to a session bean's business interface can
be passed as a parameter or as a return value of a business interface
method. It contains methods to initialize a session bean's state and
to notify the EJB container when the reference is no more needed and
can be removed. The business interfaces are two types:<dl><dlentry>
<dt>Remote business interface:</dt>
<dd>The client can run on a different machine or different <tm
tmclass="special" tmowner="Sun Microsystems, Inc." tmtype="tm"
trademark="Java">Java</tm> virtual machine than the enterprise bean
it accesses and the location of the bean is transparent.</dd>
</dlentry><dlentry>
<dt>Local business interface:</dt>
<dd>The client must run on the same <tm tmclass="special"
tmowner="Sun Microsystems, Inc." tmtype="tm" trademark="Java">Java</tm> virtual
machine as the bean it accesses and the location of the enterprise
bean is not transparent.</dd>
</dlentry><dlentry>
<dt>No-interface View:</dt><?Pub Caret 17?>
<dd>This is a variation of the Local view that exposes the public
methods of the  bean class without the use of a separate business
interface.</dd>
</dlentry></dl></dd>
</dlentry></dl> <dl><dlentry>
<dt>Mapped name</dt>
<dd>Specifies the bean's global JNDI name. The use of mappedName attribute
allows you to assign names which you can use to search the EJB bean
through the remote client.</dd>
</dlentry></dl> <dl><dlentry>
<dt>Transaction type</dt>
<dd>The <b>Transaction type</b> field is used to specify whether the
transaction is handled by the <b>Container</b> or the <b>Bean</b>.</dd>
</dlentry></dl> <dl><dlentry>
<dt>Home and Components Interfaces</dt>
<dd>Home and component interfaces are used only for EJB 2.x session
beans.<dl><dlentry>
<dt>Home interface:</dt>
<dd>The home interface allows a client to create, remove and find
existing instances of enterprise beans.</dd>
</dlentry><dlentry>
<dt>Component interface:</dt>
<dd>The component interface allows a client to access the business
methods of the enterprise bean.</dd>
</dlentry></dl></dd>
</dlentry></dl></postreq>
</taskbody>
</task>
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