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/*
* Copyright 2000-2013 Vaadin Ltd.
*
* 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 com.vaadin.util;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
/**
* Keeps track of various thread local instances used by the framework.
*
* @author Vaadin Ltd
* @version @VERSION@
* @since 7.0.0
*/
public class CurrentInstance {
private final Object instance;
private final boolean inheritable;
private static InheritableThreadLocal<Map<Class<?>, CurrentInstance>> instances = new InheritableThreadLocal<Map<Class<?>, CurrentInstance>>() {
@Override
protected Map<Class<?>, CurrentInstance> childValue(
Map<Class<?>, CurrentInstance> parentValue) {
Map<Class<?>, CurrentInstance> value = new HashMap<Class<?>, CurrentInstance>();
// Copy all inheritable values to child map
for (Entry<Class<?>, CurrentInstance> e : parentValue.entrySet()) {
if (e.getValue().inheritable) {
value.put(e.getKey(), e.getValue());
}
}
return value;
}
@Override
protected Map<java.lang.Class<?>, CurrentInstance> initialValue() {
return new HashMap<Class<?>, CurrentInstance>();
}
};
private CurrentInstance(Object instance, boolean inheritable) {
this.instance = instance;
this.inheritable = inheritable;
}
/**
* Gets the current instance of a specific type if available.
*
* @param type
* the class to get an instance of
* @return the current instance or the provided type, or <code>null</code>
* if there is no current instance.
*/
public static <T> T get(Class<T> type) {
CurrentInstance currentInstance = instances.get().get(type);
if (currentInstance != null) {
return type.cast(currentInstance.instance);
} else {
return null;
}
}
/**
* Sets the current instance of the given type.
*
* @see #setInheritable(Class, Object)
* @see ThreadLocal
*
* @param type
* the class that should be used when getting the current
* instance back
* @param instance
* the actual instance
*/
public static <T> void set(Class<T> type, T instance) {
set(type, instance, false);
}
/**
* Sets the current inheritable instance of the given type. A current
* instance that is inheritable will be available for child threads.
*
* @see #set(Class, Object)
* @see InheritableThreadLocal
*
* @param type
* the class that should be used when getting the current
* instance back
* @param instance
* the actual instance
*/
public static <T> void setInheritable(Class<T> type, T instance) {
set(type, instance, true);
}
private static <T> void set(Class<T> type, T instance, boolean inheritable) {
if (instance == null) {
instances.get().remove(type);
} else {
assert type.isInstance(instance) : "Invald instance type";
CurrentInstance previousInstance = instances.get().put(type,
new CurrentInstance(instance, inheritable));
if (previousInstance != null) {
assert previousInstance.inheritable == inheritable : "Inheritable status mismatch for "
+ type;
}
}
}
/**
* Clears all current instances.
*/
public static void clearAll() {
instances.get().clear();
}
}
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