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JSF 2.2+ utility library
There is a newer version: 4.5.1
/*
 * Copyright OmniFaces
 *
 * 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
 *
 *     https://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.omnifaces.context;

import static java.util.Collections.emptySet;

import java.util.Collection;
import java.util.Map;
import java.util.Set;

import javax.faces.context.ExternalContext;
import javax.faces.context.ExternalContextWrapper;
import javax.faces.context.FacesContext;
import javax.faces.context.Flash;
import javax.faces.context.FlashWrapper;

import org.omnifaces.cdi.ViewScoped;
import org.omnifaces.cdi.viewscope.ViewScopeManager;
import org.omnifaces.util.Faces;
import org.omnifaces.util.Hacks;

/**
 * OmniFaces external context.
 * This external context performs the following tasks:
 * 
 * Since 2.2: Take care that the {@link Flash} will be ignored during an unload request.
 * 
Since 3.9: If {@link Faces#isSessionNew()} and {@link Hacks#isMojarraUsed()} then return patched flash which work
 * arounds Mojarra issue 4431
 * 
 *
 * @author Bauke Scholtz
 * @since 2.2
 * @see OmniExternalContextFactory
 */
public class OmniExternalContext extends ExternalContextWrapper {

	// Constants ------------------------------------------------------------------------------------------------------

	private static final Flash DUMMY_FLASH = new DummyFlash();

	// Constructors ---------------------------------------------------------------------------------------------------

	/**
	 * Construct a new OmniFaces external context around the given wrapped external context.
	 * @param wrapped The wrapped external context.
	 */
	public OmniExternalContext(ExternalContext wrapped) {
		super(wrapped);
	}

	// Actions --------------------------------------------------------------------------------------------------------

	/**
	 * If the current request is an unload request from {@link ViewScoped}, then return a dummy flash scope which does
	 * not modify the flash state, else if Mojarra is used and session is new, then return a patched flash which work
	 * arounds Mojarra issue 4431, else return the original flash scope.
	 */
	@Override
	public Flash getFlash() {
		if (ViewScopeManager.isUnloadRequest(Faces.getContext())) {
			return DUMMY_FLASH;
		}

		Flash flash = super.getFlash();

		if (Faces.isSessionNew() && Hacks.isMojarraUsed()) {
			return new PatchedFlash(flash);
		}

		return flash;
	}

	// Inner classes --------------------------------------------------------------------------------------------------

	/**
	 * Patch for https://github.com/eclipse-ee4j/mojarra/issues/4431.
	 */
	private static class PatchedFlash extends FlashWrapper {

		public PatchedFlash(Flash wrapped) {
			super(wrapped);
		}

		@Override
		public Object get(Object key) {
			try {
				return super.get(key);
			}
			catch (NullPointerException e) {
				return null;
			}
		}
	}

	/**
	 * A dummy flash class which does absolutely nothing with regard to the flash scope.
	 */
	private static class DummyFlash extends Flash {

		@Override
		public int size() {
			return 0;
		}

		@Override
		public boolean isEmpty() {
			return true;
		}

		@Override
		public boolean containsKey(Object key) {
			return false;
		}

		@Override
		public boolean containsValue(Object value) {
			return false;
		}

		@Override
		public Object get(Object key) {
			return null;
		}

		@Override
		public Object put(String key, Object value) {
			return null;
		}

		@Override
		public Object remove(Object key) {
			return null;
		}

		@Override
		public void putAll(Map m) {
			// NOOP.
		}

		@Override
		public void clear() {
			// NOOP.
		}

		@Override
		public Set keySet() {
			return emptySet();
		}

		@Override
		public Collection