package org.skywalking.apm.agent.core.plugin;
import java.util.Map;
import java.util.HashMap;
import net.bytebuddy.pool.TypePool;
/**
* The WitnessClassFinder
represents a pool of {@link TypePool}s,
* each {@link TypePool} matches a {@link ClassLoader},
* which helps to find the class define existed or not.
*
* @author wusheng
*/
public enum WitnessClassFinder {
INSTANCE;
private Map poolMap = new HashMap();
/**
* @param witnessClass
* @param classLoader for finding the witnessClass
* @return true, if the given witnessClass exists, through the given classLoader.
*/
public boolean exist(String witnessClass, ClassLoader classLoader) {
ClassLoader mappingKey = classLoader == null ? NullClassLoader.INSTANCE : classLoader;
if (!poolMap.containsKey(mappingKey)) {
synchronized (poolMap) {
if (!poolMap.containsKey(mappingKey)) {
TypePool classTypePool = classLoader == null ? TypePool.Default.ofClassPath() : TypePool.Default.of(classLoader);
poolMap.put(mappingKey, classTypePool);
}
}
}
TypePool typePool = poolMap.get(mappingKey);
TypePool.Resolution witnessClassResolution = typePool.describe(witnessClass);
return witnessClassResolution.isResolved();
}
}
final class NullClassLoader extends ClassLoader {
static NullClassLoader INSTANCE = new NullClassLoader();
}