com.atomikos.util.ClassLoadingHelper Maven / Gradle / Ivy
/**
* Copyright (C) 2000-2020 Atomikos
*
* LICENSE CONDITIONS
*
* See http://www.atomikos.com/Main/WhichLicenseApplies for details.
*/
/**
*
*/
package com.atomikos.util;
import java.beans.BeanInfo;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.MethodDescriptor;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.net.URL;
import java.util.Deque;
import java.util.HashSet;
import java.util.Set;
/**
* A helper class for class loading.
*
*
*/
public class ClassLoadingHelper {
private static Set javaLangObjectMethodNames = new HashSet<>();
static {
try {
BeanInfo infos = Introspector.getBeanInfo(java.lang.Object.class);
MethodDescriptor[] methods= infos.getMethodDescriptors();
for (MethodDescriptor methodDescriptor : methods) {
javaLangObjectMethodNames.add(methodDescriptor.getName());
}
} catch (IntrospectionException e) {
//ignore, return false
}
}
public static boolean existsInJavaObjectClass(Method method) {
return javaLangObjectMethodNames.contains(method.getName());
}
private static ClassLoader lastGoodClassLoader;
/**
* Creates a new dynamic proxy instance for the given delegate.
*
* @param classLoadersToTry
* The class loaders to try, in the specified list order.
* @param interfaces
* The interfaces to add to the returned proxy.
* @param delegate
* The underlying object that will receive the calls on the
* proxy.
* @return The proxy.
*
* @exception IllegalArgumentException
* If any of the interfaces involved could not be loaded.
*/
private static RequiredInterfaceType newProxyInstance(Deque classLoadersToTry, Class[] interfaces, InvocationHandler delegate) throws IllegalArgumentException {
RequiredInterfaceType ret = null;
ClassLoader cl = classLoadersToTry.pop();
try {
ret= (RequiredInterfaceType) Proxy.newProxyInstance(cl, interfaces, delegate);
lastGoodClassLoader = cl;
} catch (IllegalArgumentException someClassNotFound) {
if (!classLoadersToTry.isEmpty()) {
// try with remaining class loaders
ret = newProxyInstance(classLoadersToTry, interfaces, delegate);
} else {
// rethrow to caller
throw someClassNotFound;
}
}
return ret;
}
private static boolean fallbackToMinimumSetOfInterfaces = false;
private static RequiredInterfaceType newProxyInstanceStartingWithLastGoodClassLoader(Deque classLoadersToTry, Class[] interfaces, InvocationHandler delegate) throws IllegalArgumentException {
RequiredInterfaceType ret = null;
if (lastGoodClassLoader != null) { //see case 151842
try {
ret = (RequiredInterfaceType) Proxy.newProxyInstance(lastGoodClassLoader, interfaces, delegate);
} catch (IllegalArgumentException someClassNotFound) {
//happens if lastGoodClassLoader is no longer valid
}
}
if (ret == null) { //try the whole list
ret = newProxyInstance(classLoadersToTry, interfaces, delegate);
}
return ret;
}
/**
* Creates a new dynamic proxy instance for the given delegate.
*
* @param classLoadersToTry
* The class loaders to try, in the specified list order.
* @param requiredInterfaceType
* The minimum interface required, if not all interface
* classes were found.
* @param interfaces
* The interfaces to add to the returned proxy.
* @param delegate
* The underlying object that will receive the calls on the
* proxy.
* @return The proxy.
*
* @exception IllegalArgumentException
* If any of the interfaces involved could not be loaded.
*/
public static RequiredInterfaceType newProxyInstance(Deque classLoadersToTry,
Class requiredInterfaceType, Class[] interfaces,
InvocationHandler delegate) throws IllegalArgumentException {
RequiredInterfaceType ret = null;
if(fallbackToMinimumSetOfInterfaces) {
Class[] minimumSetOfInterfaces = {requiredInterfaceType};
ret = newProxyInstanceStartingWithLastGoodClassLoader(classLoadersToTry, minimumSetOfInterfaces, delegate);
} else {
try {
ret = newProxyInstanceStartingWithLastGoodClassLoader(classLoadersToTry, interfaces, delegate);
} catch (IllegalArgumentException | IllegalAccessError someClassNotFound) {
fallbackToMinimumSetOfInterfaces = true;
Class[] minimumSetOfInterfaces = {requiredInterfaceType};
ret = newProxyInstanceStartingWithLastGoodClassLoader(classLoadersToTry, minimumSetOfInterfaces, delegate);
}
}
return ret;
}
/**
* Loads a class with the given name.
*
* @param className
* @return The class object
* @throws ClassNotFoundException
* If not found
*/
public static Class loadClass(String className)
throws ClassNotFoundException {
Class clazz = null;
try {
clazz = (Class)Thread.currentThread().getContextClassLoader()
.loadClass(className);
} catch (ClassNotFoundException nf) {
clazz = (Class)Class.forName(className);
}
return clazz;
}
/**
* Attempts to load a given resource from the classpath.
*
* @param clazz
* The class to use as reference re classpath.
* @param resourceName
* The name of the resource
* @return The URL to the resource, or null if not found.
*/
public static URL loadResourceFromClasspath(Class clazz, String resourceName) {
URL ret = null;
// first try from package scope
ret = clazz.getResource(resourceName);
if (ret == null) {
// not found in package -> try from absolute path
ret = clazz.getResource("/" + resourceName);
}
return ret;
}
public static Object newInstance(String className) {
try {
Class clazz = ClassLoadingHelper.loadClass(className);
return clazz.newInstance();
} catch (ClassNotFoundException e) {
//don't print stackTrace - cf bug 118228
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
return null;
}
}