org.apache.tiles.request.reflect.ClassUtil 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.tiles.request.reflect;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import java.beans.BeanInfo;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.util.Map;
/**
* Utilities to work with dynamic class loading and instantiation.
*/
public final class ClassUtil {
private static final Logger LOG = LogManager.getLogger(ClassUtil.class);
/**
* Constructor, private to avoid instantiation.
*/
private ClassUtil() {
}
/**
* Returns the class and casts it to the correct subclass.
* It tries to use the thread's current classloader first and, if it does
* not succeed, uses the classloader of ClassUtil.
*
* @param The subclass to use.
* @param className The name of the class to load.
* @param baseClass The base class to subclass to.
* @return The loaded class.
* @throws ClassNotFoundException If the class has not been found.
*/
public static Class getClass(String className, Class baseClass) throws ClassNotFoundException {
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
if (classLoader == null) {
classLoader = ClassUtil.class.getClassLoader();
}
return Class.forName(className, true, classLoader).asSubclass(baseClass);
}
/**
* Returns an instance of the given class name, by calling the default
* constructor.
*
* @param className The class name to load and to instantiate.
* @return The new instance of the class name.
* @throws CannotInstantiateObjectException If something goes wrong during
* instantiation.
*/
public static Object instantiate(String className) {
return instantiate(className, false);
}
/**
* Returns an instance of the given class name, by calling the default
* constructor.
*
* @param className The class name to load and to instantiate.
* @param returnNull If true, if the class is not found it
* returns true, otherwise it throws a
* TilesException.
* @return The new instance of the class name.
* @throws CannotInstantiateObjectException If something goes wrong during instantiation.
*/
public static Object instantiate(String className, boolean returnNull) {
try {
Class namedClass = getClass(className, Object.class);
return namedClass.newInstance();
} catch (ClassNotFoundException e) {
if (returnNull) {
return null;
}
throw new CannotInstantiateObjectException("Unable to resolve factory class: '" + className + "'", e);
} catch (IllegalAccessException e) {
throw new CannotInstantiateObjectException("Unable to access factory class: '" + className + "'", e);
} catch (InstantiationException e) {
throw new CannotInstantiateObjectException("Unable to instantiate factory class: '" + className + "'. Make sure that this class has a default constructor", e);
}
}
/**
* Collects bean infos from a class and filling a list.
*
* @param clazz The class to be inspected.
* @param name2descriptor The map in the form: name of the property -> descriptor.
*/
public static void collectBeanInfo(Class clazz, Map name2descriptor) {
BeanInfo info = null;
try {
info = Introspector.getBeanInfo(clazz);
} catch (Exception ex) {
LOG.debug("Cannot inspect class " + clazz, ex);
}
if (info == null) {
return;
}
for (PropertyDescriptor pd : info.getPropertyDescriptors()) {
pd.setValue("type", pd.getPropertyType());
pd.setValue("resolvableAtDesignTime", Boolean.TRUE);
name2descriptor.put(pd.getName(), pd);
}
}
}