/*
* 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 org.apache.wicket;
import java.util.Map;
import org.apache.wicket.request.target.resource.ResourceStreamRequestTarget;
import org.apache.wicket.util.resource.IResourceStream;
import org.apache.wicket.util.time.Time;
import org.apache.wicket.util.value.ValueMap;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* A Resource is something that implements IResourceListener and provides a
* getResource() method which returns the raw IResource to be rendered back to
* the client browser.
* <p>
* Resources themselves do not currently have URLs. Instead, they are referred
* to by components that have URLs.
* <p>
* Resources can be shared throughout an application by adding them to
* Application with addResource(Class scope, String name) or addResource(String
* name). A resource added in such a way is a named resource and is accessible
* throughout the application via Application.getResource(Class scope, String
* name) or Application.getResource(String name). The ResourceReference class
* enables easy access to such resources in a way that is light on clusters.
* <p>
* While resources can be shared between components, it is important to
* emphasize that components <i>cannot </i> be shared among containers. For
* example, you can create a button image resource with new
* DefaultButtonImageResource(...) and store that in the Application with
* addResource(). You can then assign that logical resource via
* ResourceReference to several ImageButton components. While the button image
* resource can be shared between components like this, the ImageButton
* components in this example are like all other components in Wicket and cannot
* be shared.
*
* @author Jonathan Locke
* @author Johan Compagner
* @author Gili Tzabari
* @author Igor Vaynberg
*/
public abstract class Resource implements IResourceListener
{
private static final long serialVersionUID = 1L;
/** Logger */
private static final Logger log = LoggerFactory.getLogger(Resource.class);
/** True if this resource can be cached */
private boolean cacheable;
/**
* ThreadLocal to keep any parameters associated with the request for this
* resource
*/
private static final ThreadLocal parameters = new ThreadLocal();
/**
* Constructor
*/
protected Resource()
{
// By default all resources are cacheable
cacheable = true;
}
/**
* @return Gets the resource to render to the requester
*/
public abstract IResourceStream getResourceStream();
/**
* @return boolean True or False if this resource is cacheable
*/
public final boolean isCacheable()
{
return cacheable;
}
/**
* THIS METHOD IS NOT PART OF THE WICKET PUBLIC API. DO NOT CALL IT.
*
* Called when a resource is requested.
*/
public final void onResourceRequested()
{
try
{
// Get request cycle
final RequestCycle cycle = RequestCycle.get();
// Fetch resource from subclass if necessary
IResourceStream resourceStream = init();
// Get servlet response to use when responding with resource
final Response response = cycle.getResponse();
// FIXME WICKET-385 Move HTTP caching features out of org.apache.wicket.Resource
if (isCacheable())
{
response.setLastModifiedTime(resourceStream.lastModifiedTime());
}
else
{
response.setLastModifiedTime(Time.valueOf(-1));
}
configureResponse(response);
cycle.setRequestTarget(new ResourceStreamRequestTarget(resourceStream));
}
finally
{
// Really really really make sure parameters are cleared
parameters.set(null);
}
}
/**
* Should this resource be cacheable, so will it set the last modified and
* the some cache headers in the response.
*
* @param cacheable
* boolean if the lastmodified and cache headers must be set.
* @return this
*/
public final Resource setCacheable(boolean cacheable)
{
this.cacheable = cacheable;
return this;
}
/**
* THIS METHOD IS NOT PART OF THE WICKET PUBLIC API. DO NOT USE IT!
*
* @param parameters
* Map of query parameters that paramterize this resource
*/
public final void setParameters(final Map parameters)
{
if (parameters == null)
{
Resource.parameters.set(null);
}
else
{
Resource.parameters.set(new ValueMap(parameters));
}
}
/**
* Allows implementations to do configure the response, like setting headers
* etc.
*
* @param response
* the respone
*/
protected void configureResponse(final Response response)
{
}
/**
* @return Any query parameters associated with the request for this
* resource
*/
protected ValueMap getParameters()
{
if (parameters.get() == null)
{
setParameters(RequestCycle.get().getRequest().getParameterMap());
}
return (ValueMap)parameters.get();
}
/**
* Sets any loaded resource to null, thus forcing a reload on the next
* request.
*/
protected void invalidate()
{
}
/**
* Set resource field by calling subclass
*
* @return The resource stream for the current request
*/
private final IResourceStream init()
{
IResourceStream stream = getResourceStream();
if (stream == null)
{
throw new WicketRuntimeException("Could not get resource stream");
}
return stream;
}
}