package org.apache.velocity.util.introspection;
/*
* 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.
*/
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.HashMap;
import java.util.Map;
import org.apache.commons.lang.text.StrBuilder;
import org.apache.velocity.runtime.log.Log;
import org.apache.velocity.util.MapFactory;
/**
* A cache of introspection information for a specific class instance.
* Keys {@link java.lang.reflect.Method} objects by a concatenation of the
* method name and the names of classes that make up the parameters.
*
* @author <a href="mailto:[email protected]">Jason van Zyl</a>
* @author <a href="mailto:[email protected]">Bob McWhirter</a>
* @author <a href="mailto:[email protected]">Attila Szegedi</a>
* @author <a href="mailto:[email protected]">Geir Magnusson Jr.</a>
* @author <a href="mailto:[email protected]">Henning P. Schmiedehausen</a>
* @author Nathan Bubna
* @version $Id: ClassMap.java 778038 2009-05-23 21:52:50Z nbubna $
*/
public class ClassMap
{
/** Set true if you want to debug the reflection code */
private static final boolean debugReflection = false;
/** Class logger */
private final Log log;
/**
* Class passed into the constructor used to as
* the basis for the Method map.
*/
private final Class clazz;
private final MethodCache methodCache;
/**
* Standard constructor
* @param clazz The class for which this ClassMap gets constructed.
*/
public ClassMap(final Class clazz, final Log log)
{
this.clazz = clazz;
this.log = log;
if (debugReflection && log.isDebugEnabled())
{
log.debug("=================================================================");
log.debug("== Class: " + clazz);
}
methodCache = createMethodCache();
if (debugReflection && log.isDebugEnabled())
{
log.debug("=================================================================");
}
}
/**
* Returns the class object whose methods are cached by this map.
*
* @return The class object whose methods are cached by this map.
*/
public Class getCachedClass()
{
return clazz;
}
/**
* Find a Method using the method name and parameter objects.
*
* @param name The method name to look up.
* @param params An array of parameters for the method.
* @return A Method object representing the method to invoke or null.
* @throws MethodMap.AmbiguousException When more than one method is a match for the parameters.
*/
public Method findMethod(final String name, final Object[] params)
throws MethodMap.AmbiguousException
{
return methodCache.get(name, params);
}
/**
* Populate the Map of direct hits. These
* are taken from all the public methods
* that our class, its parents and their implemented interfaces provide.
*/
private MethodCache createMethodCache()
{
MethodCache methodCache = new MethodCache(log);
//
// Looks through 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(;;) ...
for (Class classToReflect = getCachedClass(); classToReflect != null ; classToReflect = classToReflect.getSuperclass())
{
if (Modifier.isPublic(classToReflect.getModifiers()))
{
populateMethodCacheWith(methodCache, classToReflect);
}
Class [] interfaces = classToReflect.getInterfaces();
for (int i = 0; i < interfaces.length; i++)
{
populateMethodCacheWithInterface(methodCache, interfaces[i]);
}
}
// return the already initialized cache
return methodCache;
}
/* recurses up interface heirarchy to get all super interfaces (VELOCITY-689) */
private void populateMethodCacheWithInterface(MethodCache methodCache, Class iface)
{
if (Modifier.isPublic(iface.getModifiers()))
{
populateMethodCacheWith(methodCache, iface);
}
Class[] supers = iface.getInterfaces();
for (int i=0; i < supers.length; i++)
{
populateMethodCacheWithInterface(methodCache, supers[i]);
}
}
private void populateMethodCacheWith(MethodCache methodCache, Class classToReflect)
{
if (debugReflection && log.isDebugEnabled())
{
log.debug("Reflecting " + classToReflect);
}
try
{
Method[] methods = classToReflect.getDeclaredMethods();
for (int i = 0; i < methods.length; i++)
{
int modifiers = methods[i].getModifiers();
if (Modifier.isPublic(modifiers))
{
methodCache.put(methods[i]);
}
}
}
catch (SecurityException se) // Everybody feels better with...
{
if (log.isDebugEnabled())
{
log.debug("While accessing methods of " + classToReflect + ": ", se);
}
}
}
/**
* This is the cache to store and look up the method information.
*
* @author <a href="mailto:[email protected]">Henning P. Schmiedehausen</a>
* @version $Id: ClassMap.java 778038 2009-05-23 21:52:50Z nbubna $
*/
private static final class MethodCache
{
private static final Object CACHE_MISS = new Object();
private static final String NULL_ARG = Object.class.getName();
private static final Map convertPrimitives = new HashMap();
static
{
convertPrimitives.put(Boolean.TYPE, Boolean.class.getName());
convertPrimitives.put(Byte.TYPE, Byte.class.getName());
convertPrimitives.put(Character.TYPE, Character.class.getName());
convertPrimitives.put(Double.TYPE, Double.class.getName());
convertPrimitives.put(Float.TYPE, Float.class.getName());
convertPrimitives.put(Integer.TYPE, Integer.class.getName());
convertPrimitives.put(Long.TYPE, Long.class.getName());
convertPrimitives.put(Short.TYPE, Short.class.getName());
}
/** Class logger */
private final Log log;
/**
* Cache of Methods, or CACHE_MISS, keyed by method
* name and actual arguments used to find it.
*/
private final Map cache = MapFactory.create(false);
/** Map of methods that are searchable according to method parameters to find a match */
private final MethodMap methodMap = new MethodMap();
private MethodCache(Log log)
{
this.log = log;
}
/**
* 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 name The method name to look up.
* @param params An array of parameters for the method.
* @return A Method object representing the method to invoke or null.
* @throws MethodMap.AmbiguousException When more than one method is a match for the parameters.
*/
public Method get(final String name, final Object [] params)
throws MethodMap.AmbiguousException
{
String methodKey = makeMethodKey(name, params);
Object cacheEntry = cache.get(methodKey);
if (cacheEntry == CACHE_MISS)
{
// We looked this up before and failed.
return null;
}
if (cacheEntry == null)
{
try
{
// That one is expensive...
cacheEntry = methodMap.find(name, params);
}
catch(MethodMap.AmbiguousException ae)
{
/*
* that's a miss :-)
*/
cache.put(methodKey, CACHE_MISS);
throw ae;
}
cache.put(methodKey,
(cacheEntry != null) ? cacheEntry : CACHE_MISS);
}
// Yes, this might just be null.
return (Method) cacheEntry;
}
private void put(Method method)
{
String methodKey = makeMethodKey(method);
// We don't overwrite methods because we fill the
// cache from defined class towards java.lang.Object
// and that would cause overridden methods to appear
// as if they were not overridden.
if (cache.get(methodKey) == null)
{
cache.put(methodKey, method);
methodMap.add(method);
if (debugReflection && log.isDebugEnabled())
{
log.debug("Adding " + method);
}
}
}
/**
* Make a methodKey for the given method using
* the concatenation of the name and the
* types of the method parameters.
*
* @param method to be stored as key
* @return key for ClassMap
*/
private String makeMethodKey(final Method method)
{
Class[] parameterTypes = method.getParameterTypes();
int args = parameterTypes.length;
if (args == 0)
{
return method.getName();
}
StrBuilder methodKey = new StrBuilder((args+1)*16).append(method.getName());
for (int j = 0; j < args; j++)
{
/*
* 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.
*
* The lookup map (convertPrimitives) contains all eight
* primitives (boolean, byte, char, double, float, int, long, short)
* known to Java. So it should never return null for the key passed in.
*/
if (parameterTypes[j].isPrimitive())
{
methodKey.append((String) convertPrimitives.get(parameterTypes[j]));
}
else
{
methodKey.append(parameterTypes[j].getName());
}
}
return methodKey.toString();
}
private String makeMethodKey(String method, Object[] params)
{
int args = params.length;
if (args == 0)
{
return method;
}
StrBuilder methodKey = new StrBuilder((args+1)*16).append(method);
for (int j = 0; j < args; j++)
{
Object arg = params[j];
if (arg == null)
{
methodKey.append(NULL_ARG);
}
else
{
methodKey.append(arg.getClass().getName());
}
}
return methodKey.toString();
}
}
}
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