/*
* 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.devutils.stateless;
import org.apache.wicket.Component;
import org.apache.wicket.MarkupContainer;
import org.apache.wicket.Page;
import org.apache.wicket.application.IComponentOnBeforeRenderListener;
import org.apache.wicket.behavior.Behavior;
import org.apache.wicket.util.lang.Classes;
import org.apache.wicket.util.string.StringList;
import org.apache.wicket.util.visit.IVisit;
import org.apache.wicket.util.visit.IVisitor;
/**
* Stateless checker. Checks if components with {@link StatelessComponent} annotation are really
* stateless. This is a utility that is intended for use primarily during development. If you add an
* instance of this class to your application, it will check all components or pages marked with the
* <tt>StatelessComponent</tt> annotation to make sure that they are stateless as you intended.
*
* This is useful when trying to maintain stateless pages since it is very easy to inadvertently add
* a component to a page that internally uses stateful links, etc.
*
* @author Marat Radchenko
* @see StatelessComponent
*/
public class StatelessChecker implements IComponentOnBeforeRenderListener
{
/**
* Returns <code>true</code> if checker must check given component, <code>false</code>
* otherwise.
*
* @param component
* component to check.
* @return <code>true</code> if checker must check given component.
*/
protected boolean mustCheck(final Component component)
{
final StatelessComponent ann = component.getClass().getAnnotation(StatelessComponent.class);
return (ann != null) && ann.enabled();
}
/**
* @see org.apache.wicket.application.IComponentOnBeforeRenderListener#onBeforeRender(org.apache.wicket.Component)
*/
@Override
public void onBeforeRender(final Component component)
{
if (mustCheck(component))
{
final IVisitor<Component, Component> visitor = new IVisitor<Component, Component>()
{
@Override
public void component(final Component comp, final IVisit<Component> visit)
{
if ((component instanceof Page) && mustCheck(comp))
{
// Do not go deeper, because this component will be
// checked by checker
// itself.
// Actually we could go deeper but that would mean we
// traverse it twice
// (for current component and for inspected one).
// We go deeper for Page because full tree will be
// inspected during
// isPageStateless call.
visit.dontGoDeeper();
}
else if (!comp.isStateless())
{
visit.stop(comp);
}
else
{
// continue
}
}
};
final String msg = "'" + component + "' claims to be stateless but isn't.";
if (component.isStateless() == false)
{
StringList statefulBehaviors = new StringList();
for (Behavior b : component.getBehaviors())
{
if (b.getStatelessHint(component) == false)
{
statefulBehaviors.add(Classes.name(b.getClass()));
}
}
String reason;
if (statefulBehaviors.size() == 0)
{
reason = " Possible reason: no stateless hint";
}
else
{
reason = " Stateful behaviors: " + statefulBehaviors.join();
}
throw new IllegalStateException(msg + reason);
}
if (component instanceof MarkupContainer)
{
// Traverse children
final Object o = ((MarkupContainer)component).visitChildren(visitor);
if (o != null)
{
throw new IllegalArgumentException(msg + " Offending component: " + o);
}
}
if (component instanceof Page)
{
final Page p = (Page)component;
if (!p.isBookmarkable())
{
throw new IllegalArgumentException(msg +
" Only bookmarkable pages can be stateless");
}
if (!p.isPageStateless())
{
throw new IllegalArgumentException(msg + " for unknown reason");
}
}
}
}
}