org.metawidget.inspector.impl.propertystyle.BasePropertyStyle 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.propertystyle;
import java.util.Collections;
import java.util.Map;
import java.util.regex.Pattern;
import org.metawidget.util.CollectionUtils;
/**
* Convenience implementation for PropertyStyles.
*
* Handles caching, excluding names and types, and unwrapping proxies.
*
* @author Richard Kennard
*/
public abstract class BasePropertyStyle
implements PropertyStyle {
//
// Private members
//
/**
* Cache of property lookups.
*
* Property lookups are potentially expensive, so we cache them. The cache itself is a member
* variable, not a static, because we rely on BaseObjectInspector and
* ConfigReader to only create one instance of PropertyStyle for all
* Inspectors.
*
* This also stops problems with subclasses of BasePropertyStyle 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.
*/
/* package private */final Map, Map> mPropertiesCache;
private Pattern mExcludeBaseType;
//
// Constructor
//
protected BasePropertyStyle( BasePropertyStyleConfig config ) {
if ( config.isCacheProperties() ) {
mPropertiesCache = CollectionUtils.newWeakHashMap();
} else {
mPropertiesCache = null;
}
mExcludeBaseType = config.getExcludeBaseType();
}
//
// Public methods
//
public Map getProperties( Class clazz ) {
if ( mPropertiesCache == null ) {
return getUncachedProperties( clazz );
}
synchronized ( mPropertiesCache ) {
Map properties = getCachedProperties( clazz );
if ( properties == null ) {
properties = getUncachedProperties( clazz );
cacheProperties( clazz, properties );
}
return properties;
}
}
/**
* SPI for tools such as FakeReplace that
* need to clear the properties 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() {
if ( mPropertiesCache == null ) {
return;
}
synchronized ( mPropertiesCache ) {
mPropertiesCache.clear();
}
}
//
// Protected methods
//
/**
* Whether to exclude the given property, of the given type, in the given class, when searching
* for properties.
*
* This can be useful when the convention or base class define properties that are
* framework-specific, and should be filtered out from 'real' business model properties.
*
* By default, calls isExcludedReturnType and isExcludedName and
* returns true if either of them return true. Returns false otherwise.
*
* @return true if the property should be excluded, false otherwise
*/
protected boolean isExcluded( Class classToExclude, String propertyName, Class propertyType ) {
if ( isExcludedBaseType( classToExclude ) ) {
return true;
}
if ( isExcludedReturnType( propertyType ) ) {
return true;
}
if ( isExcludedName( propertyName ) ) {
return true;
}
return false;
}
/**
* Whether to exclude the given base type when searching up the model inheritance chain.
*
* This can be useful when the base types define properties that are framework-specific, and
* should be filtered out from 'real' business model properties.
*
* By default, excludes any base types from
* BasePropertyStyleConfig.setExcludeBaseType.
*
* @return true if the property should be excluded, false otherwise
*/
protected boolean isExcludedBaseType( Class classToExclude ) {
String className = classToExclude.getName();
if ( mExcludeBaseType != null && mExcludeBaseType.matcher( className ).matches() ) {
return true;
}
return false;
}
/**
* Whether to exclude the given property name when searching for properties.
*
* This can be useful when the convention defines properties that are framework-specific (eg.
* getClass()), and should be filtered out from 'real' business model properties.
*
* By default, does not exclude any names.
*
* @param name
* to consider for exclusion
* @return true if the property should be excluded, false otherwise
*/
protected boolean isExcludedName( String name ) {
return false;
}
/**
* Whether to exclude the given property return type when searching for properties.
*
* This can be useful when the convention or base class define properties that are
* framework-specific, and should be filtered out from 'real' business model properties.
*
* By default, does not exclude any return types.
*
* @param clazz
* return type to consider for exclusion
* @return true if the property should be excluded, false otherwise
*/
protected boolean isExcludedReturnType( Class clazz ) {
return false;
}
/**
* 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 inspectProperties is used when inspecting the interfaces of a
* proxied class. For each interface, it delegates to the single-class version of this method
* (ie. inspectProperties( Class )).
*/
protected Map inspectProperties( Class[] classes ) {
Map propertiesToReturn = CollectionUtils.newTreeMap();
for ( Class clazz : classes ) {
Map properties = getCachedProperties( clazz );
if ( properties == null ) {
properties = inspectProperties( clazz );
cacheProperties( clazz, properties );
}
propertiesToReturn.putAll( properties );
}
return propertiesToReturn;
}
/**
* @return the properties of the given class. Never null.
*/
protected abstract Map inspectProperties( Class clazz );
protected Map getCachedProperties( Class clazz ) {
return mPropertiesCache.get( clazz );
}
protected void cacheProperties( Class clazz, Map properties ) {
mPropertiesCache.put( clazz, Collections.unmodifiableMap( properties ) );
}
protected Map getUncachedProperties( Class clazz ) {
// If the class is not a proxy...
if ( !isProxy( clazz ) ) {
// ...inspect it normally
return inspectProperties( clazz );
}
// ...otherwise, if the superclass is not just java.lang.Object...
Class superclass = clazz.getSuperclass();
if ( !superclass.equals( Object.class ) ) {
// ...inspect the superclass
Map properties = getCachedProperties( superclass );
if ( properties == null ) {
properties = inspectProperties( superclass );
cacheProperties( superclass, properties );
}
return properties;
}
// ...otherwise, inspect each interface and merge
return inspectProperties( clazz.getInterfaces() );
}
}