org.springframework.beans.CachedIntrospectionResults Maven / Gradle / Ivy
/*
* Copyright 2002-2005 the original author or authors.
*
* Licensed 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.springframework.beans;
import java.beans.BeanInfo;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.ref.Reference;
import java.lang.ref.WeakReference;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.WeakHashMap;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/**
* Class to cache PropertyDescriptor information for a Java class.
* Package-visible; not for use by application code.
*
* Necessary as Introspector.getBeanInfo() in JDK 1.3 will return a new
* deep copy of the BeanInfo every time we ask for it. We take the opportunity
* to hash property descriptors by method name for fast lookup. Furthermore,
* we do our own caching of descriptors here, rather than rely on the JDK's
* system-wide BeanInfo cache (to avoid leaks on class loader shutdown).
*
*
Information is cached statically, so we don't need to create new
* objects of this class for every JavaBean we manipulate. Thus this class
* implements the factory design pattern, using a private constructor
* and a static forClass method to obtain instances.
*
* @author Rod Johnson
* @author Juergen Hoeller
* @since 05 May 2001
*/
final class CachedIntrospectionResults {
private static final Log logger = LogFactory.getLog(CachedIntrospectionResults.class);
/**
* Map keyed by class containing CachedIntrospectionResults.
* Needs to be a WeakHashMap with WeakReferences as values to allow
* for proper garbage collection in case of multiple classloaders.
*/
private static final Map classCache = Collections.synchronizedMap(new WeakHashMap());
/**
* We might use this from the EJB tier, so we don't want to use synchronization.
* Object references are atomic, so we can live with doing the occasional
* unnecessary lookup at startup only.
*/
static CachedIntrospectionResults forClass(Class clazz) throws BeansException {
CachedIntrospectionResults results = null;
Object value = classCache.get(clazz);
if (value instanceof Reference) {
Reference ref = (Reference) value;
results = (CachedIntrospectionResults) ref.get();
}
else {
results = (CachedIntrospectionResults) value;
}
if (results == null) {
// can throw BeansException
results = new CachedIntrospectionResults(clazz);
boolean cacheSafe = isCacheSafe(clazz);
if (logger.isDebugEnabled()) {
logger.debug("Class [" + clazz.getName() + "] is " + (!cacheSafe ? "not " : "") + "cache-safe");
}
if (cacheSafe) {
classCache.put(clazz, results);
}
else {
classCache.put(clazz, new WeakReference(results));
}
}
else {
if (logger.isDebugEnabled()) {
logger.debug("Using cached introspection results for class [" + clazz.getName() + "]");
}
}
return results;
}
/**
* Check whether the given class is cache-safe,
* i.e. whether it is loaded by the same class loader as the
* CachedIntrospectionResults class or a parent of it.
*
Many thanks to Guillaume Poirier for pointing out the
* garbage collection issues and for suggesting this solution.
* @param clazz the class to analyze
* @return whether the given class is thread-safe
*/
private static boolean isCacheSafe(Class clazz) {
ClassLoader cur = CachedIntrospectionResults.class.getClassLoader();
ClassLoader target = clazz.getClassLoader();
if (target == null || cur == target) {
return true;
}
while (cur != null) {
cur = cur.getParent();
if (cur == target) {
return true;
}
}
return false;
}
private final BeanInfo beanInfo;
/** Property descriptors keyed by property name */
private final Map propertyDescriptorCache;
/**
* Create new CachedIntrospectionResults instance fot the given class.
*/
private CachedIntrospectionResults(Class clazz) throws BeansException {
try {
if (logger.isDebugEnabled()) {
logger.debug("Getting BeanInfo for class [" + clazz.getName() + "]");
}
this.beanInfo = Introspector.getBeanInfo(clazz);
// Immediately remove class from Introspector cache, to allow for proper
// garbage collection on class loader shutdown - we cache it here anyway,
// in a GC-friendly manner. In contrast to CachedIntrospectionResults,
// Introspector does not use WeakReferences as values of its WeakHashMap!
Class classToFlush = clazz;
do {
Introspector.flushFromCaches(classToFlush);
classToFlush = classToFlush.getSuperclass();
}
while (classToFlush != null);
if (logger.isDebugEnabled()) {
logger.debug("Caching PropertyDescriptors for class [" + clazz.getName() + "]");
}
this.propertyDescriptorCache = new HashMap();
// This call is slow so we do it once.
PropertyDescriptor[] pds = this.beanInfo.getPropertyDescriptors();
for (int i = 0; i < pds.length; i++) {
if (logger.isDebugEnabled()) {
logger.debug("Found property '" + pds[i].getName() + "'" +
(pds[i].getPropertyType() != null ?
" of type [" + pds[i].getPropertyType().getName() + "]" : "") +
(pds[i].getPropertyEditorClass() != null ?
"; editor [" + pds[i].getPropertyEditorClass().getName() + "]" : ""));
}
// Set methods accessible if declaring class is not public, for example
// in case of package-protected base classes that define bean properties.
Method readMethod = pds[i].getReadMethod();
if (readMethod != null && !Modifier.isPublic(readMethod.getDeclaringClass().getModifiers())) {
readMethod.setAccessible(true);
}
Method writeMethod = pds[i].getWriteMethod();
if (writeMethod != null && !Modifier.isPublic(writeMethod.getDeclaringClass().getModifiers())) {
writeMethod.setAccessible(true);
}
this.propertyDescriptorCache.put(pds[i].getName(), pds[i]);
}
}
catch (IntrospectionException ex) {
throw new FatalBeanException("Cannot get BeanInfo for object of class [" + clazz.getName() + "]", ex);
}
}
BeanInfo getBeanInfo() {
return this.beanInfo;
}
Class getBeanClass() {
return this.beanInfo.getBeanDescriptor().getBeanClass();
}
PropertyDescriptor getPropertyDescriptor(String propertyName) {
return (PropertyDescriptor) this.propertyDescriptorCache.get(propertyName);
}
}