org.apache.commons.jexl2.internal.introspection.IntrospectorBase Maven / Gradle / Ivy
/*
* 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.Method;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.util.Map;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import org.apache.commons.logging.Log;
/**
* This basic function of this class is to return a Method object for a
* particular class given the name of a method and the parameters to the method
* in the form of an Object[]
*
* The first time the Introspector sees a class it creates a class method map
* for the class in question. Basically the class method map is a Hastable where
* Method objects are keyed by a concatenation of the method name and the names
* of classes that make up the parameters.
*
* For example, a method with the following signature:
*
* public void method(String a, StringBuffer b)
*
* would be mapped by the key:
*
* "method" + "java.lang.String" + "java.lang.StringBuffer"
*
* This mapping is performed for all the methods in a class and stored.
* @since 1.0
*/
public class IntrospectorBase {
/** the logger. */
protected final Log rlog;
/**
* Holds the method maps for the classes we know about, keyed by Class.
*/
private final Map, ClassMap> classMethodMaps = new HashMap, ClassMap>();
/**
* The class loader used to solve constructors if needed.
*/
private ClassLoader loader;
/**
* Holds the map of classes ctors we know about as well as unknown ones.
*/
private final Map> constructorsMap = new HashMap>();
/**
* Holds the set of classes we have introspected.
*/
private final Map> constructibleClasses = new HashMap>();
/**
* Create the introspector.
* @param log the logger to use
*/
public IntrospectorBase(Log log) {
this.rlog = log;
loader = getClass().getClassLoader();
}
/**
* Gets a class by name through this introspector class loader.
* @param className the class name
* @return the class instance or null if it could not be found
*/
public Class getClassByName(String className) {
try {
return Class.forName(className, false, loader);
} catch (ClassNotFoundException xignore) {
return null;
}
}
/**
* Gets the method defined by the MethodKey for the class c.
*
* @param c Class in which the method search is taking place
* @param key Key of the method being searched for
* @return The desired method object
* @throws MethodKey.AmbiguousException if no unambiguous method could be found through introspection
*/
public Method getMethod(Class c, MethodKey key) {
try {
ClassMap classMap = getMap(c);
return classMap.findMethod(key);
} catch (MethodKey.AmbiguousException xambiguous) {
// whoops. Ambiguous. Make a nice log message and return null...
if (rlog != null && rlog.isInfoEnabled()) {
rlog.info("ambiguous method invocation: "
+ c.getName() + "."
+ key.debugString(), xambiguous);
}
return null;
}
}
/**
* Gets the field named by key for the class c.
*
* @param c Class in which the field search is taking place
* @param key Name of the field being searched for
* @return the desired field or null if it does not exist or is not accessible
* */
public Field getField(Class c, String key) {
ClassMap classMap = getMap(c);
return classMap.findField(c, key);
}
/**
* Gets the array of accessible field names known for a given class.
* @param c the class
* @return the class field names
*/
public String[] getFieldNames(Class c) {
if (c == null) {
return new String[0];
}
ClassMap classMap = getMap(c);
return classMap.getFieldNames();
}
/**
* Gets the array of accessible methods names known for a given class.
* @param c the class
* @return the class method names
*/
public String[] getMethodNames(Class c) {
if (c == null) {
return new String[0];
}
ClassMap classMap = getMap(c);
return classMap.getMethodNames();
}
/**
* Gets the array of accessible method known for a given class.
* @param c the class
* @param methodName the method name
* @return the array of methods (null or not empty)
*/
public Method[] getMethods(Class c, String methodName) {
if (c == null) {
return null;
}
ClassMap classMap = getMap(c);
return classMap.get(methodName);
}
/**
* A Constructor get cache-miss.
*/
private static class CacheMiss {
/** The constructor used as cache-miss. */
@SuppressWarnings("unused")
public CacheMiss() {}
}
/** The cache-miss marker for the constructors map. */
private static final Constructor CTOR_MISS = CacheMiss.class.getConstructors()[0];
/**
* Sets the class loader used to solve constructors.
* Also cleans the constructors and methods caches.
* @param cloader the class loader; if null, use this instance class loader
*/
public void setLoader(ClassLoader cloader) {
ClassLoader previous = loader;
if (cloader == null) {
cloader = getClass().getClassLoader();
}
if (!cloader.equals(loader)) {
// clean up constructor and class maps
synchronized (constructorsMap) {
Iterator>> entries = constructorsMap.entrySet().iterator();
while (entries.hasNext()) {
Map.Entry> entry = entries.next();
Class clazz = entry.getValue().getDeclaringClass();
if (isLoadedBy(previous, clazz)) {
entries.remove();
// the method name is the name of the class
constructibleClasses.remove(entry.getKey().getMethod());
}
}
}
// clean up method maps
synchronized (classMethodMaps) {
Iterator, ClassMap>> entries = classMethodMaps.entrySet().iterator();
while (entries.hasNext()) {
Map.Entry, ClassMap> entry = entries.next();
Class clazz = entry.getKey();
if (isLoadedBy(previous, clazz)) {
entries.remove();
}
}
}
loader = cloader;
}
}
/**
* Checks whether a class is loaded through a given class loader or one of its ascendants.
* @param loader the class loader
* @param clazz the class to check
* @return true if clazz was loaded through the loader, false otherwise
*/
private static boolean isLoadedBy(ClassLoader loader, Class clazz) {
if (loader != null) {
ClassLoader cloader = clazz.getClassLoader();
while (cloader != null) {
if (cloader.equals(loader)) {
return true;
} else {
cloader = cloader.getParent();
}
}
}
return false;
}
/**
* Gets the constructor defined by the MethodKey.
*
* @param key Key of the constructor being searched for
* @return The desired constructor object
* or null if no unambiguous constructor could be found through introspection.
*/
public Constructor getConstructor(final MethodKey key) {
return getConstructor(null, key);
}
/**
* Gets the constructor defined by the MethodKey.
* @param c the class we want to instantiate
* @param key Key of the constructor being searched for
* @return The desired constructor object
* or null if no unambiguous constructor could be found through introspection.
*/
public Constructor getConstructor(final Class c, final MethodKey key) {
Constructor ctor = null;
synchronized (constructorsMap) {
ctor = constructorsMap.get(key);
// that's a clear miss
if (CTOR_MISS.equals(ctor)) {
return null;
}
// let's introspect...
if (ctor == null) {
final String cname = key.getMethod();
// do we know about this class?
Class clazz = constructibleClasses.get(cname);
try {
// do find the most specific ctor
if (clazz == null) {
if (c != null && c.getName().equals(key.getMethod())) {
clazz = c;
} else {
clazz = loader.loadClass(cname);
}
// add it to list of known loaded classes
constructibleClasses.put(cname, clazz);
}
List> l = new LinkedList>();
for (Constructor ictor : clazz.getConstructors()) {
l.add(ictor);
}
// try to find one
ctor = key.getMostSpecificConstructor(l);
if (ctor != null) {
constructorsMap.put(key, ctor);
} else {
constructorsMap.put(key, CTOR_MISS);
}
} catch (ClassNotFoundException xnotfound) {
if (rlog != null && rlog.isInfoEnabled()) {
rlog.info("unable to find class: "
+ cname + "."
+ key.debugString(), xnotfound);
}
ctor = null;
} catch (MethodKey.AmbiguousException xambiguous) {
if (rlog != null && rlog.isInfoEnabled()) {
rlog.info("ambiguous constructor invocation: "
+ cname + "."
+ key.debugString(), xambiguous);
}
ctor = null;
}
}
return ctor;
}
}
/**
* Gets the ClassMap for a given class.
* @param c the class
* @return the class map
*/
private ClassMap getMap(Class c) {
synchronized (classMethodMaps) {
ClassMap classMap = classMethodMaps.get(c);
if (classMap == null) {
classMap = new ClassMap(c, rlog);
classMethodMaps.put(c, classMap);
}
return classMap;
}
}
}