org.metawidget.inspector.impl.actionstyle.BaseActionStyle Maven / Gradle / Ivy
// Metawidget
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
package org.metawidget.inspector.impl.actionstyle;
import java.util.Collections;
import java.util.Map;
import org.metawidget.util.CollectionUtils;
/**
* Convenience implementation for ActionStyles.
*
* Handles caching, and unwrapping proxies.
*
* @author Richard Kennard
*/
public abstract class BaseActionStyle
implements ActionStyle {
//
// Private members
//
/**
* Cache of Action lookups.
*
* Action lookups are potentially expensive, so we cache them. The cache itself is a member
* variable, not a static, because we rely on BaseObjectInspector to only create
* one instance of ActionStyle for all Inspectors.
*
* This also stops problems with subclasses of BaseActionStyle sharing the same
* static cache.
*
* Note: the cache is unbounded, because the number of Classes in the system is fixed. This even
* applies to hot deployment products such as FakeReplace, because new Classes are replaced such
* that they .equal() their originals.
*/
private final Map, Map> mActionCache = CollectionUtils.newWeakHashMap();
//
// Public methods
//
public Map getActions( Class clazz ) {
synchronized ( mActionCache ) {
Map actions = getCachedActions( clazz );
if ( actions == null ) {
// If the class is not a proxy...
if ( !isProxy( clazz ) ) {
// ...inspect it normally
actions = inspectActions( clazz );
} else {
// ...otherwise, if the superclass is not just java.lang.Object...
Class superclass = clazz.getSuperclass();
if ( !superclass.equals( Object.class ) ) {
// ...inspect the superclass
actions = getCachedActions( superclass );
if ( actions == null ) {
actions = inspectActions( superclass );
cacheActions( superclass, actions );
}
} else {
// ...otherwise, inspect each interface and merge
actions = inspectActions( clazz.getInterfaces() );
}
}
// Cache the result
cacheActions( clazz, actions );
}
return actions;
}
}
/**
* SPI for tools such as FakeReplace that
* need to clear the action cache.
*
* This does not affect the immutability of the PropertyStyle, as its external behaviour is
* unchanged (it will just be a little slower the next time it is called, while it re-caches).
*/
public void clearCache() {
synchronized ( mActionCache ) {
mActionCache.clear();
}
}
//
// Protected methods
//
/**
* Returns true if the given class is a 'proxy' of its original self.
*
* Proxied classes generally don't carry annotations, so it is important to traverse away from
* the proxied class back to the original class before inspection.
*
* By default, returns true for classes with _$$_javassist_ or
* ByCGLIB$$ in their name.
*/
protected boolean isProxy( Class clazz ) {
// (don't use .getSimpleName or .contains, for J2SE 1.4 compatibility)
String name = clazz.getName();
if ( name.indexOf( "_$$_javassist_" ) != -1 ) {
return true;
}
if ( name.indexOf( "ByCGLIB$$" ) != -1 ) {
return true;
}
return false;
}
/**
* Inspect the given Classes and merge their results.
*
* This version of inspectActions is used when inspecting the interfaces of a
* proxied class.
*/
protected Map inspectActions( Class[] classes ) {
Map actionsToReturn = CollectionUtils.newTreeMap();
for ( Class clazz : classes ) {
Map actions = getCachedActions( clazz );
if ( actions == null ) {
actions = inspectActions( clazz );
cacheActions( clazz, actions );
}
actionsToReturn.putAll( actions );
}
return actionsToReturn;
}
/**
* @return the properties of the given class. Never null.
*/
protected abstract Map inspectActions( Class clazz );
protected Map getCachedActions( Class clazz ) {
return mActionCache.get( clazz );
}
protected void cacheActions( Class clazz, Map actions ) {
mActionCache.put( clazz, Collections.unmodifiableMap( actions ) );
}
}