io.grpc.internal.ReflectionLongAdderCounter Maven / Gradle / Ivy
/*
* Copyright 2017 The gRPC Authors
*
* Licensed 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 io.grpc.internal;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* A {@link LongCounter} that is implemented with a JDK8 {@link LongAdder}. Instantiates the object
* and invokes methods reflectively to avoid a compile time dependency on LongAdder.
*/
public final class ReflectionLongAdderCounter implements LongCounter {
private static final Logger logger = Logger.getLogger(ReflectionLongAdderCounter.class.getName());
private static final Constructor defaultConstructor;
private static final Method addMethod;
private static final Method sumMethod;
private static final RuntimeException initializationException;
private final Object instance;
static {
Class klass = null;
Constructor defaultConstructorLookup = null;
Method addMethodLookup = null;
Method sumMethodLookup = null;
Throwable caught = null;
try {
klass = Class.forName("java.util.concurrent.atomic.LongAdder");
addMethodLookup = klass.getMethod("add", Long.TYPE);
sumMethodLookup = klass.getMethod("sum");
Constructor[] constructors = klass.getConstructors();
for (Constructor ctor : constructors) {
if (ctor.getParameterTypes().length == 0) {
defaultConstructorLookup = ctor;
break;
}
}
} catch (Throwable e) {
logger.log(
Level.FINE,
"LongAdder can not be found via reflection, this is normal for JDK7 and below",
e);
caught = e;
}
if (caught == null && defaultConstructorLookup != null) {
defaultConstructor = defaultConstructorLookup;
addMethod = addMethodLookup;
sumMethod = sumMethodLookup;
initializationException = null;
} else {
defaultConstructor = null;
addMethod = null;
sumMethod = null;
initializationException = new RuntimeException(caught);
}
}
ReflectionLongAdderCounter() {
if (initializationException != null) {
throw initializationException;
}
try {
instance = defaultConstructor.newInstance();
} catch (InstantiationException e) {
throw new RuntimeException(e);
} catch (IllegalAccessException e) {
throw new RuntimeException(e);
} catch (InvocationTargetException e) {
throw new RuntimeException(e);
}
}
/**
* Returns true if the environment supports LongAdder. In other words, we are running in >= JDK8.
*/
static boolean isAvailable() {
return initializationException == null;
}
private static final Object[] one = new Object[] { 1L };
@Override
public void add(long delta) {
try {
addMethod.invoke(instance, delta == 1L ? one : new Object[] { delta });
} catch (IllegalAccessException e) {
throw new RuntimeException(e);
} catch (InvocationTargetException e) {
throw new RuntimeException(e);
}
}
@Override
public long value() {
try {
return (Long) sumMethod.invoke(instance);
} catch (IllegalAccessException e) {
throw new RuntimeException();
} catch (InvocationTargetException e) {
throw new RuntimeException();
}
}
}