/*

 * Copyright 2002-2012 the original author or authors.

 *

 * 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 org.springframework.web.context.request;

import javax.faces.context.FacesContext;

import org.springframework.core.NamedInheritableThreadLocal;

import org.springframework.core.NamedThreadLocal;

import org.springframework.util.ClassUtils;

/**

 * Holder class to expose the web request in the form of a thread-bound

 * {@link RequestAttributes} object. The request will be inherited

 * by any child threads spawned by the current thread if the

 * {@code inheritable} flag is set to {@code true}.

 *

 * <p>Use {@link RequestContextListener} or

 * {@link org.springframework.web.filter.RequestContextFilter} to expose

 * the current web request. Note that

 * {@link org.springframework.web.servlet.DispatcherServlet} and

 * {@link org.springframework.web.portlet.DispatcherPortlet} already

 * expose the current request by default.

 *

 * @author Juergen Hoeller

 * @author Rod Johnson

 * @since 2.0

 * @see RequestContextListener

 * @see org.springframework.web.filter.RequestContextFilter

 * @see org.springframework.web.servlet.DispatcherServlet

 * @see org.springframework.web.portlet.DispatcherPortlet

 */

public abstract class RequestContextHolder  {

    private static final boolean jsfPresent =

            ClassUtils.isPresent("javax.faces.context.FacesContext", RequestContextHolder.class.getClassLoader());

    private static final ThreadLocal<RequestAttributes> requestAttributesHolder =

            new NamedThreadLocal<RequestAttributes>("Request attributes");

    private static final ThreadLocal<RequestAttributes> inheritableRequestAttributesHolder =

            new NamedInheritableThreadLocal<RequestAttributes>("Request context");

    /**

     * Reset the RequestAttributes for the current thread.

     */

    public static void resetRequestAttributes() {

        requestAttributesHolder.remove();

        inheritableRequestAttributesHolder.remove();

    }

    /**

     * Bind the given RequestAttributes to the current thread,

     * <i>not</i> exposing it as inheritable for child threads.

     * @param attributes the RequestAttributes to expose

     * @see #setRequestAttributes(RequestAttributes, boolean)

     */

    public static void setRequestAttributes(RequestAttributes attributes) {

        setRequestAttributes(attributes, false);

    }

    /**

     * Bind the given RequestAttributes to the current thread.

     * @param attributes the RequestAttributes to expose,

     * or {@code null} to reset the thread-bound context

     * @param inheritable whether to expose the RequestAttributes as inheritable

     * for child threads (using an {@link InheritableThreadLocal})

     */

    public static void setRequestAttributes(RequestAttributes attributes, boolean inheritable) {

        if (attributes == null) {

            resetRequestAttributes();

        }

        else {

            if (inheritable) {

                inheritableRequestAttributesHolder.set(attributes);

                requestAttributesHolder.remove();

            }

            else {

                requestAttributesHolder.set(attributes);

                inheritableRequestAttributesHolder.remove();

            }

        }

    }

    /**

     * Return the RequestAttributes currently bound to the thread.

     * @return the RequestAttributes currently bound to the thread,

     * or {@code null} if none bound

     */

    public static RequestAttributes getRequestAttributes() {

        RequestAttributes attributes = requestAttributesHolder.get();

        if (attributes == null) {

            attributes = inheritableRequestAttributesHolder.get();

        }

        return attributes;

    }

    /**

     * Return the RequestAttributes currently bound to the thread.

     * <p>Exposes the previously bound RequestAttributes instance, if any.

     * Falls back to the current JSF FacesContext, if any.

     * @return the RequestAttributes currently bound to the thread

     * @throws IllegalStateException if no RequestAttributes object

     * is bound to the current thread

     * @see #setRequestAttributes

     * @see ServletRequestAttributes

     * @see FacesRequestAttributes

     * @see javax.faces.context.FacesContext#getCurrentInstance()

     */

    public static RequestAttributes currentRequestAttributes() throws IllegalStateException {

        RequestAttributes attributes = getRequestAttributes();

        if (attributes == null) {

            if (jsfPresent) {

                attributes = FacesRequestAttributesFactory.getFacesRequestAttributes();

            }

            if (attributes == null) {

                throw new IllegalStateException("No thread-bound request found: " +

                        "Are you referring to request attributes outside of an actual web request, " +

                        "or processing a request outside of the originally receiving thread? " +

                        "If you are actually operating within a web request and still receive this message, " +

                        "your code is probably running outside of DispatcherServlet/DispatcherPortlet: " +

                        "In this case, use RequestContextListener or RequestContextFilter to expose the current request.");

            }

        }

        return attributes;

    }

    /**

     * Inner class to avoid hard-coded JSF dependency.

      */

    private static class FacesRequestAttributesFactory {

        public static RequestAttributes getFacesRequestAttributes() {

            FacesContext facesContext = FacesContext.getCurrentInstance();

            return (facesContext != null ? new FacesRequestAttributes(facesContext) : null);

        }

    }

}