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/*
* 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.faces.context;
import java.util.Iterator;
import javax.el.ELContext;
import javax.faces.application.FacesMessage;
/**
* see Javadoc of JSF Specification
*
* @author Manfred Geiler (latest modification by $Author: skitching $)
* @version $Revision: 676298 $ $Date: 2008-07-13 05:31:48 -0500 (Sun, 13 Jul 2008) $
*/
public abstract class FacesContext
{
/**
* Return the context within which all EL-expressions are evaluated.
*
* A JSF implementation is expected to provide a full implementation of this
* class. However JSF also explicitly allows user code to apply the "decorator"
* pattern to this type, by overriding the FacesContextFactory class. In that
* pattern, the decorating class has a reference to an "underlying" implementation
* and forward calls to it, possibly after taking other related actions.
*
* The decorator pattern does have difficulties with backwards-compatibility when
* new methods are added to the class being decorated, as with this method which
* was added in JSF1.2. Decorator classes that were written for JSF1.1 will subclass
* this class, but will not override this method to pass the call on to the
* "underlying" instance. This base implementation therefore must do that for it.
*
* Unfortunately the JSF designers stuffed up the design; this base class has no way
* of knowing what the "underlying" instance is! The current implementation here
* is therefore to delegate directly to the very first FacesContext instance
* registered within this request (via setCurrentInstance). This instance should
* be the "full" implementation provided by the JSF framework. The drawback is that
* when any decorator class is present which defaults to this base implementation,
* then any following decorator instances that do override this method do not get
* it invoked.
*
* It is believed that the Sun JSF implementation (Mojarra) does something similar.
*
* @since 1.2
*/
public ELContext getELContext()
{
// Do NOT use getCurrentInstance here. For FacesContext decorators that
// register themselves as "the current instance" that will cause an
// infinite loop. For FacesContext decorators that do not register
// themselves as "the current instance", if they are themselves wrapped
// by a decorator that *does* register itself, then an infinite loop
// also occurs.
//
// As noted above, we really want to do something like
// ctx = getWrappedInstance();
// where the subclass can return the object it is delegating to.
// As there is no such method, however, the best we can do is pass the
// method call on to the first-registered FacesContext instance. That
// instance will never be "this", as the real original FacesContext
// object will provide a proper implementation of this method.
FacesContext ctx = _firstInstance.get();
if (ctx == null)
{
throw new NullPointerException(FacesContext.class.getName());
}
ELContext elctx = ctx.getELContext();
if (elctx == null)
{
throw new UnsupportedOperationException();
}
return elctx;
}
public abstract javax.faces.application.Application getApplication();
public abstract Iterator getClientIdsWithMessages();
public abstract javax.faces.context.ExternalContext getExternalContext();
public abstract FacesMessage.Severity getMaximumSeverity();
public abstract Iterator getMessages();
public abstract Iterator getMessages(String clientId);
public abstract javax.faces.render.RenderKit getRenderKit();
public abstract boolean getRenderResponse();
public abstract boolean getResponseComplete();
public abstract javax.faces.context.ResponseStream getResponseStream();
public abstract void setResponseStream(javax.faces.context.ResponseStream responseStream);
public abstract javax.faces.context.ResponseWriter getResponseWriter();
public abstract void setResponseWriter(javax.faces.context.ResponseWriter responseWriter);
public abstract javax.faces.component.UIViewRoot getViewRoot();
public abstract void setViewRoot(javax.faces.component.UIViewRoot root);
public abstract void addMessage(String clientId,
javax.faces.application.FacesMessage message);
public abstract void release();
public abstract void renderResponse();
public abstract void responseComplete();
private static ThreadLocal _currentInstance = new ThreadLocal()
{
protected FacesContext initialValue()
{
return null;
}
};
private static ThreadLocal _firstInstance = new ThreadLocal()
{
protected FacesContext initialValue()
{
return null;
}
};
public static FacesContext getCurrentInstance()
{
return _currentInstance.get();
}
protected static void setCurrentInstance(javax.faces.context.FacesContext context)
{
if (context == null)
{
_currentInstance.remove();
_firstInstance.remove();
}
else
{
_currentInstance.set(context);
if (_firstInstance.get() == null)
{
_firstInstance.set(context);
}
}
}
}