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Jexl is an implementation of the JSTL Expression Language with extensions.
/*
* 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.commons.jexl2.internal.introspection;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import org.apache.commons.logging.Log;
/**
* A cache of introspection information for a specific class instance.
* Keys objects by an agregation of the method name and the classes
* that make up the parameters.
*
* Originally taken from the Velocity tree so we can be self-sufficient.
*
* @see MethodKey
*
* @author Jason van Zyl
* @author Bob McWhirter
* @author Attila Szegedi
* @author Geir Magnusson Jr.
* @author Henning P. Schmiedehausen
* @version $Id: ClassMap.java 896952 2010-01-07 18:21:29Z henrib $
* @since 1.0
*/
final class ClassMap {
/** cache of methods. */
private final MethodCache methodCache;
/** cache of fields. */
private final Map fieldCache;
/**
* Standard constructor.
*
* @param aClass the class to deconstruct.
* @param log the logger.
*/
ClassMap(Class aClass, Log log) {
// eagerly cache methods
methodCache = createMethodCache(aClass, log);
// eagerly cache public fields
fieldCache = createFieldCache(aClass);
}
/**
* Find a Field using its name.
* The clazz parameter must be this ClassMap key.
* @param clazz the class to introspect
* @param fname the field name
* @return A Field object representing the field to invoke or null.
*/
Field findField(final Class clazz, final String fname) {
return fieldCache.get(fname);
}
/**
* Gets the field names cached by this map.
* @return the array of field names
*/
String[] getFieldNames() {
return fieldCache.keySet().toArray(new String[fieldCache.size()]);
}
/**
* Creates a map of all public fields of a given class.
* @param clazz the class to introspect
* @return the map of fields (may be the empty map, can not be null)
*/
private static Map createFieldCache(Class clazz) {
Field[] fields = clazz.getFields();
if (fields.length > 0) {
Map cache = new HashMap();
for(Field field : fields) {
cache.put(field.getName(), field);
}
return cache;
} else {
return Collections.emptyMap();
}
}
/**
* Gets the methods names cached by this map.
* @return the array of method names
*/
String[] getMethodNames() {
return methodCache.names();
}
/**
* Find a Method using the method name and parameter objects.
*
* @param key the method key
* @return A Method object representing the method to invoke or null.
* @throws MethodKey.AmbiguousException When more than one method is a match for the parameters.
*/
Method findMethod(final MethodKey key)
throws MethodKey.AmbiguousException {
return methodCache.get(key);
}
/**
* Populate the Map of direct hits. These are taken from all the public methods
* that our class, its parents and their implemented interfaces provide.
* @param classToReflect the class to cache
* @param log the Log
* @return a newly allocated & filled up cache
*/
private static MethodCache createMethodCache(Class classToReflect, Log log) {
//
// Build a list of all elements in the class hierarchy. This one is bottom-first (i.e. we start
// with the actual declaring class and its interfaces and then move up (superclass etc.) until we
// hit java.lang.Object. That is important because it will give us the methods of the declaring class
// which might in turn be abstract further up the tree.
//
// We also ignore all SecurityExceptions that might happen due to SecurityManager restrictions (prominently
// hit with Tomcat 5.5).
//
// We can also omit all that complicated getPublic, getAccessible and upcast logic that the class map had up
// until Velocity 1.4. As we always reflect all elements of the tree (that's what we have a cache for), we will
// hit the public elements sooner or later because we reflect all the public elements anyway.
//
// Ah, the miracles of Java for(;;) ...
MethodCache cache = new MethodCache();
for (;classToReflect != null; classToReflect = classToReflect.getSuperclass()) {
if (Modifier.isPublic(classToReflect.getModifiers())) {
populateMethodCacheWith(cache, classToReflect, log);
}
Class[] interfaces = classToReflect.getInterfaces();
for (int i = 0; i < interfaces.length; i++) {
populateMethodCacheWithInterface(cache, interfaces[i], log);
}
}
return cache;
}
/**
* Recurses up interface hierarchy to get all super interfaces.
* @param cache the cache to fill
* @param iface the interface to populate the cache from
* @param log the Log
*/
private static void populateMethodCacheWithInterface(MethodCache cache, Class iface, Log log) {
if (Modifier.isPublic(iface.getModifiers())) {
populateMethodCacheWith(cache, iface, log);
}
Class[] supers = iface.getInterfaces();
for (int i = 0; i < supers.length; i++) {
populateMethodCacheWithInterface(cache, supers[i], log);
}
}
/**
* Recurses up class hierarchy to get all super classes.
* @param cache the cache to fill
* @param clazz the class to populate the cache from
* @param log the Log
*/
private static void populateMethodCacheWith(MethodCache cache, Class clazz, Log log) {
try {
Method[] methods = clazz.getDeclaredMethods();
for (int i = 0; i < methods.length; i++) {
int modifiers = methods[i].getModifiers();
if (Modifier.isPublic(modifiers)) {
cache.put(methods[i]);
}
}
} catch (SecurityException se) {
// Everybody feels better with...
if (log.isDebugEnabled()) {
log.debug("While accessing methods of " + clazz + ": ", se);
}
}
}
/**
* This is the cache to store and look up the method information.
*
* @author Henning P. Schmiedehausen
* @version $Id: ClassMap.java 896952 2010-01-07 18:21:29Z henrib $
*
* It stores the association between:
* - a key made of a method name & an array of argument types.
* - a method.
*
*
* Since the invocation of the associated method is dynamic, there is no need (nor way) to differentiate between
* foo(int,int) & foo(Integer,Integer) since in practise, only the latter form will be used through a call.
* This of course, applies to all 8 primitive types.
*
* @version $Id: ClassMap.java 896952 2010-01-07 18:21:29Z henrib $
*/
static final class MethodCache {
/**
* A method that returns itself used as a marker for cache miss,
* allows the underlying cache map to be strongly typed.
* @return itself as a method
*/
public static Method cacheMiss() {
try {
return MethodCache.class.getMethod("cacheMiss");
} catch (Exception xio) {
// this really cant make an error...
return null;
}
}
/** The cache miss marker method. */
private static final Method CACHE_MISS = cacheMiss();
/** The initial size of the primitive conversion map. */
private static final int PRIMITIVE_SIZE = 13;
/** The primitive type to class conversion map. */
private static final Map, Class> PRIMITIVE_TYPES;
static {
PRIMITIVE_TYPES = new HashMap, Class>(PRIMITIVE_SIZE);
PRIMITIVE_TYPES.put(Boolean.TYPE, Boolean.class);
PRIMITIVE_TYPES.put(Byte.TYPE, Byte.class);
PRIMITIVE_TYPES.put(Character.TYPE, Character.class);
PRIMITIVE_TYPES.put(Double.TYPE, Double.class);
PRIMITIVE_TYPES.put(Float.TYPE, Float.class);
PRIMITIVE_TYPES.put(Integer.TYPE, Integer.class);
PRIMITIVE_TYPES.put(Long.TYPE, Long.class);
PRIMITIVE_TYPES.put(Short.TYPE, Short.class);
}
/** Converts a primitive type to its corresponding class.
*
* If the argument type is primitive then we want to convert our
* primitive type signature to the corresponding Object type so
* introspection for methods with primitive types will work
* correctly.
*
* @param parm a may-be primitive type class
* @return the equivalent object class
*/
static Class primitiveClass(Class parm) {
// it is marginally faster to get from the map than call isPrimitive...
//if (!parm.isPrimitive()) return parm;
Class prim = PRIMITIVE_TYPES.get(parm);
return prim == null ? parm : prim;
}
/**
* The method cache.
*
* Cache of Methods, or CACHE_MISS, keyed by method
* name and actual arguments used to find it.
*
*/
private final Map methods = new HashMap();
/**
* Map of methods that are searchable according to method parameters to find a match.
*/
private final MethodMap methodMap = new MethodMap();
/**
* Find a Method using the method name and parameter objects.
*
* Look in the methodMap for an entry. If found,
* it'll either be a CACHE_MISS, in which case we
* simply give up, or it'll be a Method, in which
* case, we return it.
*
*
* If nothing is found, then we must actually go
* and introspect the method from the MethodMap.
*
* @param methodKey the method key
* @return A Method object representing the method to invoke or null.
* @throws MethodKey.AmbiguousException When more than one method is a match for the parameters.
*/
Method get(final MethodKey methodKey) throws MethodKey.AmbiguousException {
synchronized (methodMap) {
Method cacheEntry = methods.get(methodKey);
// We looked this up before and failed.
if (cacheEntry == CACHE_MISS) {
return null;
}
if (cacheEntry == null) {
try {
// That one is expensive...
cacheEntry = methodMap.find(methodKey);
if (cacheEntry != null) {
methods.put(methodKey, cacheEntry);
} else {
methods.put(methodKey, CACHE_MISS);
}
} catch (MethodKey.AmbiguousException ae) {
// that's a miss :-)
methods.put(methodKey, CACHE_MISS);
throw ae;
}
}
// Yes, this might just be null.
return cacheEntry;
}
}
/**
* Adds a method to the map.
* @param method the method to add
*/
void put(Method method) {
synchronized (methodMap) {
MethodKey methodKey = new MethodKey(method);
// We don't overwrite methods. Especially not if we fill the
// cache from defined class towards java.lang.Object because
// abstract methods in superclasses would else overwrite concrete
// classes further down the hierarchy.
if (methods.get(methodKey) == null) {
methods.put(methodKey, method);
methodMap.add(method);
}
}
}
/**
* Gets all the method names from this map.
* @return the array of method name
*/
String[] names() {
synchronized (methodMap) {
return methodMap.names();
}
}
}
}