https://github.com/spring-projects/spring-framework: Spring Web (Spring IO)
  • Juergen Hoeller 
/*
 * 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.jsf;

import javax.faces.application.NavigationHandler;
import javax.faces.context.FacesContext;

import org.springframework.lang.Nullable;


Base class for JSF NavigationHandler implementations that want
to be capable of decorating an original NavigationHandler.

Supports the standard JSF style of decoration (through a constructor argument) as well as an overloaded handleNavigation method with explicit NavigationHandler argument (passing in the original NavigationHandler). Subclasses are forced to implement this overloaded handleNavigation method. Standard JSF invocations will automatically delegate to the overloaded method, with the constructor-injected NavigationHandler as argument. 
Author:Juergen Hoeller
See Also:
Since:1.2.7
/**
 * Base class for JSF NavigationHandler implementations that want
 * to be capable of decorating an original NavigationHandler.
 *
 * <p>Supports the standard JSF style of decoration (through a constructor argument)
 * as well as an overloaded {@code handleNavigation} method with explicit
 * NavigationHandler argument (passing in the original NavigationHandler). Subclasses
 * are forced to implement this overloaded {@code handleNavigation} method.
 * Standard JSF invocations will automatically delegate to the overloaded method,
 * with the constructor-injected NavigationHandler as argument.
 *
 * @author Juergen Hoeller
 * @since 1.2.7
 * @see #handleNavigation(javax.faces.context.FacesContext, String, String, NavigationHandler)
 * @see DelegatingNavigationHandlerProxy
 */
public abstract class DecoratingNavigationHandler extends NavigationHandler {

	@Nullable
	private NavigationHandler decoratedNavigationHandler;


	
Create a DecoratingNavigationHandler without fixed original NavigationHandler.

/**
	 * Create a DecoratingNavigationHandler without fixed original NavigationHandler.
	 */
	protected DecoratingNavigationHandler() {
	}

	
Create a DecoratingNavigationHandler with fixed original NavigationHandler.

Params:
  • originalNavigationHandler – the original NavigationHandler to decorate
/**
	 * Create a DecoratingNavigationHandler with fixed original NavigationHandler.
	 * @param originalNavigationHandler the original NavigationHandler to decorate
	 */
	protected DecoratingNavigationHandler(NavigationHandler originalNavigationHandler) {
		this.decoratedNavigationHandler = originalNavigationHandler;
	}

	
Return the fixed original NavigationHandler decorated by this handler, if any
(that is, if passed in through the constructor).

/**
	 * Return the fixed original NavigationHandler decorated by this handler, if any
	 * (that is, if passed in through the constructor).
	 */
	@Nullable
	public final NavigationHandler getDecoratedNavigationHandler() {
		return this.decoratedNavigationHandler;
	}


	
This implementation of the standard JSF handleNavigation method delegates to the overloaded variant, passing in constructor-injected NavigationHandler as argument. 
See Also:
/**
	 * This implementation of the standard JSF {@code handleNavigation} method
	 * delegates to the overloaded variant, passing in constructor-injected
	 * NavigationHandler as argument.
	 * @see #handleNavigation(javax.faces.context.FacesContext, String, String, javax.faces.application.NavigationHandler)
	 */
	@Override
	public final void handleNavigation(FacesContext facesContext, String fromAction, String outcome) {
		handleNavigation(facesContext, fromAction, outcome, this.decoratedNavigationHandler);
	}

	
Special handleNavigation variant with explicit NavigationHandler argument. Either called directly, by code with an explicit original handler, or called from the standard handleNavigation method, as plain JSF-defined NavigationHandler. 
Implementations should invoke callNextHandlerInChain to delegate to the next handler in the chain. This will always call the most appropriate next handler (see callNextHandlerInChain javadoc). Alternatively, the decorated NavigationHandler or the passed-in original NavigationHandler can also be called directly; however, this is not as flexible in terms of reacting to potential positions in the chain. 
Params:
  • facesContext – the current JSF context
  • fromAction – the action binding expression that was evaluated to retrieve the specified outcome, or null if the outcome was acquired by some other means
  • outcome – the logical outcome returned by a previous invoked application action (which may be null)
  • originalNavigationHandler – the original NavigationHandler, or null if none
See Also:
/**
	 * Special {@code handleNavigation} variant with explicit NavigationHandler
	 * argument. Either called directly, by code with an explicit original handler,
	 * or called from the standard {@code handleNavigation} method, as
	 * plain JSF-defined NavigationHandler.
	 * <p>Implementations should invoke {@code callNextHandlerInChain} to
	 * delegate to the next handler in the chain. This will always call the most
	 * appropriate next handler (see {@code callNextHandlerInChain} javadoc).
	 * Alternatively, the decorated NavigationHandler or the passed-in original
	 * NavigationHandler can also be called directly; however, this is not as
	 * flexible in terms of reacting to potential positions in the chain.
	 * @param facesContext the current JSF context
	 * @param fromAction the action binding expression that was evaluated to retrieve the
	 * specified outcome, or {@code null} if the outcome was acquired by some other means
	 * @param outcome the logical outcome returned by a previous invoked application action
	 * (which may be {@code null})
	 * @param originalNavigationHandler the original NavigationHandler,
	 * or {@code null} if none
	 * @see #callNextHandlerInChain
	 */
	public abstract void handleNavigation(FacesContext facesContext, @Nullable String fromAction,
			@Nullable String outcome, @Nullable NavigationHandler originalNavigationHandler);


	
Method to be called by subclasses when intending to delegate to the next
handler in the NavigationHandler chain. Will always call the most
appropriate next handler, either the decorated NavigationHandler passed
in as constructor argument or the original NavigationHandler as passed
into this method - according to the position of this instance in the chain.

Will call the decorated NavigationHandler specified as constructor
argument, if any. In case of a DecoratingNavigationHandler as target, the
original NavigationHandler as passed into this method will be passed on to
the next element in the chain: This ensures propagation of the original
handler that the last element in the handler chain might delegate back to.
In case of a standard NavigationHandler as target, the original handler
will simply not get passed on; no delegating back to the original is
possible further down the chain in that scenario.

If no decorated NavigationHandler specified as constructor argument,
this instance is the last element in the chain. Hence, this method will
call the original NavigationHandler as passed into this method. If no
original NavigationHandler has been passed in (for example if this
instance is the last element in a chain with standard NavigationHandlers
as earlier elements), this method corresponds to a no-op.

Params:
  • facesContext – the current JSF context
  • fromAction – the action binding expression that was evaluated to retrieve the specified outcome, or null if the outcome was acquired by some other means
  • outcome – the logical outcome returned by a previous invoked application action (which may be null)
  • originalNavigationHandler – the original NavigationHandler, or null if none
/**
	 * Method to be called by subclasses when intending to delegate to the next
	 * handler in the NavigationHandler chain. Will always call the most
	 * appropriate next handler, either the decorated NavigationHandler passed
	 * in as constructor argument or the original NavigationHandler as passed
	 * into this method - according to the position of this instance in the chain.
	 * <p>Will call the decorated NavigationHandler specified as constructor
	 * argument, if any. In case of a DecoratingNavigationHandler as target, the
	 * original NavigationHandler as passed into this method will be passed on to
	 * the next element in the chain: This ensures propagation of the original
	 * handler that the last element in the handler chain might delegate back to.
	 * In case of a standard NavigationHandler as target, the original handler
	 * will simply not get passed on; no delegating back to the original is
	 * possible further down the chain in that scenario.
	 * <p>If no decorated NavigationHandler specified as constructor argument,
	 * this instance is the last element in the chain. Hence, this method will
	 * call the original NavigationHandler as passed into this method. If no
	 * original NavigationHandler has been passed in (for example if this
	 * instance is the last element in a chain with standard NavigationHandlers
	 * as earlier elements), this method corresponds to a no-op.
	 * @param facesContext the current JSF context
	 * @param fromAction the action binding expression that was evaluated to retrieve the
	 * specified outcome, or {@code null} if the outcome was acquired by some other means
	 * @param outcome the logical outcome returned by a previous invoked application action
	 * (which may be {@code null})
	 * @param originalNavigationHandler the original NavigationHandler,
	 * or {@code null} if none
	 */
	protected final void callNextHandlerInChain(FacesContext facesContext, @Nullable String fromAction,
			@Nullable String outcome, @Nullable NavigationHandler originalNavigationHandler) {

		NavigationHandler decoratedNavigationHandler = getDecoratedNavigationHandler();

		if (decoratedNavigationHandler instanceof DecoratingNavigationHandler) {
			// DecoratingNavigationHandler specified through constructor argument:
			// Call it with original NavigationHandler passed in.
			DecoratingNavigationHandler decHandler = (DecoratingNavigationHandler) decoratedNavigationHandler;
			decHandler.handleNavigation(facesContext, fromAction, outcome, originalNavigationHandler);
		}
		else if (decoratedNavigationHandler != null) {
			// Standard NavigationHandler specified through constructor argument:
			// Call it through standard API, without original NavigationHandler passed in.
			// The called handler will not be able to redirect to the original handler.
			decoratedNavigationHandler.handleNavigation(facesContext, fromAction, outcome);
		}
		else if (originalNavigationHandler != null) {
			// No NavigationHandler specified through constructor argument:
			// Call original handler, marking the end of this chain.
			originalNavigationHandler.handleNavigation(facesContext, fromAction, outcome);
		}
	}

}