io.netty.util.ConstantPool Maven / Gradle / Ivy
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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including
all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and
JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up
with different versions on classes on the class path).
/*
* Copyright 2013 The Netty Project
*
* The Netty Project 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:
*
* https://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.netty.util;
import static io.netty.util.internal.ObjectUtil.checkNotNull;
import static io.netty.util.internal.ObjectUtil.checkNonEmpty;
import io.netty.util.internal.PlatformDependent;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.atomic.AtomicInteger;
/**
* A pool of {@link Constant}s.
*
* @param the type of the constant
*/
public abstract class ConstantPool> {
private final ConcurrentMap constants = PlatformDependent.newConcurrentHashMap();
private final AtomicInteger nextId = new AtomicInteger(1);
/**
* Shortcut of {@link #valueOf(String) valueOf(firstNameComponent.getName() + "#" + secondNameComponent)}.
*/
public T valueOf(Class firstNameComponent, String secondNameComponent) {
return valueOf(
checkNotNull(firstNameComponent, "firstNameComponent").getName() +
'#' +
checkNotNull(secondNameComponent, "secondNameComponent"));
}
/**
* Returns the {@link Constant} which is assigned to the specified {@code name}.
* If there's no such {@link Constant}, a new one will be created and returned.
* Once created, the subsequent calls with the same {@code name} will always return the previously created one
* (i.e. singleton.)
*
* @param name the name of the {@link Constant}
*/
public T valueOf(String name) {
return getOrCreate(checkNonEmpty(name, "name"));
}
/**
* Get existing constant by name or creates new one if not exists. Threadsafe
*
* @param name the name of the {@link Constant}
*/
private T getOrCreate(String name) {
T constant = constants.get(name);
if (constant == null) {
final T tempConstant = newConstant(nextId(), name);
constant = constants.putIfAbsent(name, tempConstant);
if (constant == null) {
return tempConstant;
}
}
return constant;
}
/**
* Returns {@code true} if a {@link AttributeKey} exists for the given {@code name}.
*/
public boolean exists(String name) {
return constants.containsKey(checkNonEmpty(name, "name"));
}
/**
* Creates a new {@link Constant} for the given {@code name} or fail with an
* {@link IllegalArgumentException} if a {@link Constant} for the given {@code name} exists.
*/
public T newInstance(String name) {
return createOrThrow(checkNonEmpty(name, "name"));
}
/**
* Creates constant by name or throws exception. Threadsafe
*
* @param name the name of the {@link Constant}
*/
private T createOrThrow(String name) {
T constant = constants.get(name);
if (constant == null) {
final T tempConstant = newConstant(nextId(), name);
constant = constants.putIfAbsent(name, tempConstant);
if (constant == null) {
return tempConstant;
}
}
throw new IllegalArgumentException(String.format("'%s' is already in use", name));
}
protected abstract T newConstant(int id, String name);
@Deprecated
public final int nextId() {
return nextId.getAndIncrement();
}
}