faceswebapplicationcontextutils.java

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/*
 * Copyright 2002-2004 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 de.mindmatters.faces.spring.context;

import java.util.Map;

import javax.faces.context.FacesContext;

/**
 * Convenience methods to retrieve the faces root FacesWebApplicationContext for
 * a given {@link javax.faces.context.FacesContext}. This is e.g. useful for
 * accessing a faces-spring context from within custom components.
 * 
 * @author Andreas Kuhrwahl
 * 
 * @see de.mindmatters.faces.spring.context.FacesWebApplicationContext
 */
public final class FacesWebApplicationContextUtils {

    /**
     * Constructor (not used).
     */
    private FacesWebApplicationContextUtils() {
        super();
    }

    /**
     * Finds the faces root FacesWebApplicationContext for this web app, which
     * is typically loaded via ContextLoaderListener.
     * <p>
     * Will rethrow an exception that happened on root context startup, to
     * differentiate between a failed context startup and no context at all.
     * </p>
     * 
     * @param context
     *            FacesContext to find the web application context for
     * @return the faces root FacesWebApplicationContext for this web app, or
     *         null if none
     * @see FacesWebApplicationContext#ROOT_FACES_WEB_APPLICATION_CONTEXT_ATTRIBUTE
     */
    public static FacesWebApplicationContext getWebApplicationContext(
            final FacesContext context) {
        Map applicationMap = context.getExternalContext().getApplicationMap();
        Object contextAttr = applicationMap
                .get(FacesWebApplicationContext.ROOT_FACES_WEB_APPLICATION_CONTEXT_ATTRIBUTE);
        if (contextAttr != null) {
            if (contextAttr instanceof RuntimeException) {
                throw (RuntimeException) contextAttr;
            }
            if (contextAttr instanceof Error) {
                throw (Error) contextAttr;
            }
            if (!(contextAttr instanceof FacesWebApplicationContext)) {
                throw new IllegalStateException(
                        "Root context attribute is not of type FacesSpringWebApplicationContext: "
                                + contextAttr);
            }
        }
        return (FacesWebApplicationContext) contextAttr;
    }

    /**
     * Finds the required faces root FacesWebApplicationContext for this web
     * app, which is typically loaded via ContextLoaderListenr.
     * <p>
     * Will rethrow an exception that happened on root context startup, to
     * differentiate between a failed context startup and no context at all.
     * </p>
     * 
     * @param context
     *            FacesContext to find the web application context for
     * @return the root WebApplicationContext for this web app
     * @throws IllegalStateException
     *             if the root FacesWebApplicationContext could not be found
     * @see FacesWebApplicationContext#ROOT_FACES_WEB_APPLICATION_CONTEXT_ATTRIBUTE
     */
    public static FacesWebApplicationContext getRequiredWebApplicationContext(
            final FacesContext context) {
        final FacesWebApplicationContext wac = getWebApplicationContext(context);
        if (wac == null) {
            throw new IllegalStateException(
                    "No FacesSpringWebApplicationContext found: no FacesSpringContextLoaderListener registered?");
        }
        return wac;
    }

}