geronimo-jcdi_2.0_spec/src/main/java/javax/enterprise/context/control/RequestContextController.java

/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you 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.control;

import javax.enterprise.context.ContextNotActiveException;

/**
 * The CDI container provides a built in instance of RequestContextController that is dependent scoped for the purposes
 * of activating and deactivating.  For example:
 *
 * <pre>
 *    &#064;Inject
 *    private RequestContextController requestContextController;
 *
 *    public void doRequest(String body) {
 *       // activate request context
 *       requestContextController.activate();
 *
 *       // do work in a request context.
 *
 *       // deactivate the request context
 *       requestContextController.deactivate();
 *    }
 * </pre>
 *
 * Once the request context has been deactivated, you may activate it once again, creating a brand new request context.
 * The activated request context is bound to the current thread, any injection points targeting a request scoped bean
 * will be satisfied with the same request scoped objects.
 *
 */
public interface RequestContextController
{
    /**
     * Activates a RequestContext for the current thread if one is not already active.
     * @return true if the context was activated by this invocation, false if not.
     */
    boolean activate();

    /**
     * Deactivates the current Request Context if it was activated by this context controller.  If the context is active
     * but was not activated by this controller, then it may not be deactivated by this controller,
     * meaning this method will do nothing.
     *
     * If the context is not active, a {@see ContextNotActiveException} is thrown.
     *
     * @throws ContextNotActiveException if the context is not active
     */
    void deactivate() throws ContextNotActiveException;
}