ConversationScoped.java

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 * Copyright 2010, Red Hat, Inc., and individual contributors
 * by the @authors tag. See the copyright.txt in the distribution for a
 * full listing of individual contributors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package javax.enterprise.context;

import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

import java.lang.annotation.Documented;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import javax.enterprise.util.AnnotationLiteral;

/**
 * <p>
 * Specifies that a bean is conversation scoped.
 * </p>
 *  <p>
 * While <tt>ConversationScoped</tt> must be associated with the built-in conversation context required by the specification,
 * third-party extensions are
 * allowed to also associate it with their own context. Behavior described below is only related to the built-in conversation context.
 * </p>
 * <p>
 * The conversation scope is active:
 * </p>
 * <ul>
 * <li>during all Servlet requests.</li>
 * </ul>
 * <p>
 * An event with qualifier <tt>@Initialized(ConversationScoped.class)</tt> is fired when the conversation context is initialized
 * and an event with qualifier <tt>@Destroyed(ConversationScoped.class)</tt> is fired when the conversation is destroyed.
 * The event payload is:
 * </p>
 * <ul>
 * <li>the conversation id if the conversation context is destroyed and is not associated with a current Servlet request, or</li>
 * <li>the <tt>ServletRequest</tt> if the application is a web application deployed to a Servlet container, or</li>
 * <li>any <tt>java.lang.Object</tt> for other types of application.</li>
 * </ul>
 *
 * <p>
 * The conversation context provides access to state associated with a particular <em>conversation</em>. Every Servlet request
 * has an associated conversation. This association is managed automatically by the container according to the following rules:
 * </p>
 *
 * <ul>
 * <li>Any Servlet request has exactly one associated conversation.</li>
 * <li>The container provides a filter with the name "CDI Conversation Filter", which may be mapped in <tt>web.xml</tt>,
 * allowing the user alter when the conversation is associated with the servlet request. If this filter is not mapped in any
 * <tt>web.xml</tt> in the application, the conversation associated with a Servlet request is determined at the beginning of the
 * request before calling any <tt>service()</tt> method of any servlet in the web application, calling the <tt>doFilter()</tt>
 * method of any servlet filter in the web application and before the container calls any <tt>ServletRequestListener</tt> or
 * <tt>AsyncListener</tt> in the web application.</li>
 * </ul>
 * <p>
 *
 * <p>
 * Any conversation is in one of two states: <em>transient</em> or <em>long-running</em>.
 * </p>
 *
 * <ul>
 * <li>By default, a conversation is transient</li>
 * <li>A transient conversation may be marked long-running by calling {@link javax.enterprise.context.Conversation#begin()}</li>
 * <li>A long-running conversation may be marked transient by calling {@link javax.enterprise.context.Conversation#end()}</li>
 * </ul>
 *
 * <p>
 * All long-running conversations have a string-valued unique identifier, which may be set by the application when the
 * conversation is marked long-running, or generated by the container.
 * </p>
 *
 * <p>
 * If the conversation associated with the current Servlet request is in the <em>transient</em> state at the end of a Servlet
 * request, it is destroyed, and the conversation context is also destroyed.
 * </p>
 *
 * <p>
 * If the conversation associated with the current Servlet request is in the <em>long-running</em> state at the end of a Servlet
 * request, it is not destroyed. The long-running conversation associated with a request may be propagated to any Servlet
 * request via use of a request parameter named <tt>cid</tt> containing the unique identifier of the conversation. In this
 * case, the application must manage this request parameter.
 * </p>
 *
 * <p>
 * If the current Servlet request is a JSF request, and the conversation is in <em>long-running</em> state, it is propagated
 * according to the following rules:
 * </p>
 *
 * <ul>
 * <li>The long-running conversation context associated with a request that renders a JSF view is automatically propagated to
 * any faces request (JSF form submission) that originates from that rendered page.</li>
 * <li>The long-running conversation context associated with a request that results in a JSF redirect (a redirect resulting from
 * a navigation rule or JSF <tt>NavigationHandler</tt>) is automatically propagated to the resulting non-faces request, and to any other
 * subsequent request to the same URL. This is accomplished via use of a request parameter named <tt>cid</tt> containing the
 * unique identifier of the conversation.</li>
 * </ul>
 *
 * <p>
 * When no conversation is propagated to a Servlet request, or if a request parameter named <tt>conversationPropagation</tt> has
 * the value <tt>none</tt> the request is associated with a new transient conversation.
 * All long-running conversations are scoped to a particular HTTP servlet session and may not cross session boundaries.
 * In the following cases, a propagated long-running conversation cannot be restored and re-associated with the request:
 * </p>
 *
 * <ul>
 * <li>When the HTTP servlet session is invalidated, all long-running conversation contexts created during the current session
 * are destroyed, after the servlet <tt>service()</tt> method completes.</li>
 * <li>The container is permitted to arbitrarily destroy any long-running conversation that is associated with no current
 * Servlet request, in order to conserve resources.</li>
 * </ul>
 *
 * @see javax.enterprise.context.Conversation
 * @see javax.enterprise.context.NonexistentConversationException
 * @see javax.enterprise.context.BusyConversationException
 *
 * @author Gavin King
 * @author Pete Muir
 * @author Antoine Sabot-Durand
 */

@Target({ TYPE, METHOD, FIELD })
@Retention(RUNTIME)
@Documented
@NormalScope(passivating = true)
@Inherited
public @interface ConversationScoped {

    /**
     * Supports inline instantiation of the {@link ConversationScoped} annotation.
     *
     * @author Martin Kouba
     * @since 2.0
     */
    public final static class Literal extends AnnotationLiteral<ConversationScoped> implements ConversationScoped {

        public static final Literal INSTANCE = new Literal();

        private static final long serialVersionUID = 1L;

    }

}