com.netflix.config.PropertyWrapper Maven / Gradle / Ivy
/**
* Copyright 2014 Netflix, Inc.
*
* 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.netflix.config;
import java.util.IdentityHashMap;
import java.util.List;
import com.google.common.collect.Lists;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.netflix.config.validation.PropertyChangeValidator;
import com.netflix.config.validation.ValidationException;
/**
* A wrapper around DynamicProperty and associates it with a type.
*
* @param The type of the DynamicProperty
* @author awang
*/
public abstract class PropertyWrapper implements Property {
protected final DynamicProperty prop;
protected final V defaultValue;
@SuppressWarnings("rawtypes")
private static final IdentityHashMap, Object> SUBCLASSES_WITH_NO_CALLBACK
= new IdentityHashMap, Object>();
private static final Logger logger = LoggerFactory.getLogger(PropertyWrapper.class);
private final List callbackList = Lists.newArrayList();
static {
PropertyWrapper.registerSubClassWithNoCallback(DynamicIntProperty.class);
PropertyWrapper.registerSubClassWithNoCallback(DynamicStringProperty.class);
PropertyWrapper.registerSubClassWithNoCallback(DynamicBooleanProperty.class);
PropertyWrapper.registerSubClassWithNoCallback(DynamicFloatProperty.class);
PropertyWrapper.registerSubClassWithNoCallback(DynamicLongProperty.class);
PropertyWrapper.registerSubClassWithNoCallback(DynamicDoubleProperty.class);
}
private static final Object DUMMY_VALUE = new Object();
/**
* By default, a subclass of PropertyWrapper will automatically register {@link #propertyChanged()} as a callback
* for property value change. This method provide a way for a subclass to avoid this overhead if it is not interested
* to get callback.
*
* @param c
*/
public static final void registerSubClassWithNoCallback(@SuppressWarnings("rawtypes") Class c) {
SUBCLASSES_WITH_NO_CALLBACK.put(c, DUMMY_VALUE);
}
protected PropertyWrapper(String propName, V defaultValue) {
this.prop = DynamicProperty.getInstance(propName);
this.defaultValue = defaultValue;
Class c = getClass();
// this checks whether this constructor is called by a class that
// extends the immediate sub classes (IntProperty, etc.) of PropertyWrapper.
// If yes, it is very likely that propertyChanged() is overriden
// in the sub class and we need to register the callback.
// Otherwise, we know that propertyChanged() does nothing in
// immediate subclasses and we can avoid registering the callback, which
// has the cost of modifying the CopyOnWriteArraySet
if (!SUBCLASSES_WITH_NO_CALLBACK.containsKey(c)) {
Runnable callback = new Runnable() {
public void run() {
propertyChanged();
}
};
this.prop.addCallback(callback);
callbackList.add(callback);
this.prop.addValidator(new PropertyChangeValidator() {
@Override
public void validate(String newValue) {
PropertyWrapper.this.validate(newValue);
}
});
try {
if (this.prop.getString() != null) {
this.validate(this.prop.getString());
}
} catch (ValidationException e) {
logger.warn("Error validating property at initialization. Will fallback to default value.", e);
prop.updateValue(defaultValue);
}
}
}
@Override
public String getName() {
return prop.getName();
}
public void addValidator(PropertyChangeValidator v) {
if (v != null) {
prop.addValidator(v);
}
}
/**
* Called when the property value is updated.
* The default does nothing.
* Subclasses are free to override this if desired.
*/
protected void propertyChanged() {
propertyChanged(getValue());
}
/**
* Called when the property value is updated.
* The default does nothing.
* Subclasses are free to override this if desired.
*/
protected void propertyChanged(V newValue) {
// by default, do nothing
}
protected void validate(String newValue) {
}
/**
* Gets the time (in milliseconds past the epoch) when the property
* was last set/changed.
*/
@Override
public long getChangedTimestamp() {
return prop.getChangedTimestamp();
}
/**
* Add the callback to be triggered when the value of the property is changed
*
* @param callback
*/
@Override
public void addCallback(Runnable callback) {
if (callback != null) {
prop.addCallback(callback);
callbackList.add(callback);
}
}
/**
* Remove all callbacks registered through this instance of property
*/
@Override
public void removeAllCallbacks() {
for (Runnable callback: callbackList) {
prop.removeCallback(callback);
}
}
/**
* Get current typed value of the property.
*/
@Override
public abstract V getValue();
@Override
public V getDefaultValue() {
return defaultValue;
}
public DynamicProperty getDynamicProperty() {
return prop;
}
@Override
public String toString() {
return "DynamicProperty: {name=" + prop.getName() + ", current value="
+ prop.getString(String.valueOf(defaultValue)) + "}";
}
}