org.apache.commons.pool2.impl.PoolImplUtils 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.pool2.impl;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import org.apache.commons.pool2.PooledObjectFactory;
/**
* Implementation specific utilities.
*
* @since 2.0
*/
class PoolImplUtils {
/**
* Identifies the concrete type of object that an object factory creates.
*
* @param factoryClass
* The factory to examine
*
* @return the type of object the factory creates
*/
@SuppressWarnings("rawtypes")
static Class getFactoryType(final Class factoryClass) {
final Class type = PooledObjectFactory.class;
final Object genericType = getGenericType(type, factoryClass);
if (genericType instanceof Integer) {
// POOL-324 org.apache.commons.pool2.impl.GenericObjectPool.getFactoryType() throws
// java.lang.ClassCastException
//
// A bit hackish, but we must handle cases when getGenericType() does not return a concrete types.
final ParameterizedType pi = getParameterizedType(type, factoryClass);
if (pi != null) {
final Type[] bounds = ((TypeVariable) pi.getActualTypeArguments()[((Integer) genericType).intValue()]).getBounds();
if (bounds != null && bounds.length > 0) {
final Type bound0 = bounds[0];
if (bound0 instanceof Class) {
return (Class) bound0;
}
}
}
// last resort: Always return a Class
return Object.class;
}
return (Class) genericType;
}
/**
* Obtains the concrete type used by an implementation of an interface that uses a generic type.
*
* @param type
* The interface that defines a generic type
* @param clazz
* The class that implements the interface with a concrete type
* @param
* The interface type
*
* @return concrete type used by the implementation
*/
private static Object getGenericType(final Class type, final Class clazz) {
if (type == null || clazz == null) {
// Error will be logged further up the call stack
return null;
}
// Look to see if this class implements the generic interface
final ParameterizedType pi = getParameterizedType(type, clazz);
if (pi != null) {
return getTypeParameter(clazz, pi.getActualTypeArguments()[0]);
}
// Interface not found on this class. Look at the superclass.
@SuppressWarnings("unchecked")
final Class superClass = (Class) clazz.getSuperclass();
final Object result = getGenericType(type, superClass);
if (result instanceof Class) {
// Superclass implements interface and defines explicit type for generic
return result;
} else if (result instanceof Integer) {
// Superclass implements interface and defines unknown type for generic
// Map that unknown type to the generic types defined in this class
final ParameterizedType superClassType = (ParameterizedType) clazz.getGenericSuperclass();
return getTypeParameter(clazz, superClassType.getActualTypeArguments()[((Integer) result).intValue()]);
} else {
// Error will be logged further up the call stack
return null;
}
}
/**
* Gets the matching parameterized type or null.
* @param type
* The interface that defines a generic type.
* @param clazz
* The class that implements the interface with a concrete type.
* @param
* The interface type.
* @return the matching parameterized type or null.
*/
private static ParameterizedType getParameterizedType(final Class type, final Class clazz) {
for (final Type iface : clazz.getGenericInterfaces()) {
// Only need to check interfaces that use generics
if (iface instanceof ParameterizedType) {
final ParameterizedType pi = (ParameterizedType) iface;
// Look for the generic interface
if (pi.getRawType() instanceof Class && type.isAssignableFrom((Class) pi.getRawType())) {
return pi;
}
}
}
return null;
}
/**
* For a generic parameter, return either the Class used or if the type is unknown, the index for the type in
* definition of the class
*
* @param clazz
* defining class
* @param argType
* the type argument of interest
*
* @return An instance of {@link Class} representing the type used by the type parameter or an instance of
* {@link Integer} representing the index for the type in the definition of the defining class
*/
private static Object getTypeParameter(final Class clazz, final Type argType) {
if (argType instanceof Class) {
return argType;
}
final TypeVariable[] tvs = clazz.getTypeParameters();
for (int i = 0; i < tvs.length; i++) {
if (tvs[i].equals(argType)) {
return Integer.valueOf(i);
}
}
return null;
}
}