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/**
* 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.ArrayList;
import java.util.Collections;
import java.util.List;
import com.google.common.base.Splitter;
import com.google.common.base.Strings;
import com.google.common.collect.Lists;
/**
* This class delegates to a regex (default is comma) delimited dynamic string property and
* returns a dynamic list of a generic type which is transformed from string.
*
* @author awang
*/
public abstract class DynamicListProperty implements Property> {
private volatile List values;
private List defaultValues;
private DynamicStringProperty delegate;
private Splitter splitter;
public static final String DEFAULT_DELIMITER = ",";
/**
* Create the dynamic list property using default delimiter regex ",". The guava Splitter used is created as
* Splitter.onPattern(delimiterRegex).omitEmptyStrings().trimResults(). The default
* list value will be transformed from list of strings after splitting. If defaultValue string is
* null, the default list value will be an empty list.
*/
public DynamicListProperty(String propName, String defaultValue) {
this(propName, defaultValue, DEFAULT_DELIMITER);
}
/**
* Create the dynamic list property. The guava Splitter used is created as
* Splitter.onPattern(delimiterRegex).omitEmptyStrings().trimResults(). The default
* list value will be transformed from list of strings after splitting. If defaultValue string is
* null, the default list value will be an empty list.
*/
public DynamicListProperty(String propName, String defaultValue, String delimiterRegex) {
this.splitter = Splitter.onPattern(delimiterRegex).omitEmptyStrings().trimResults();
setup(propName, transform(split(defaultValue)), splitter);
}
public DynamicListProperty(String propName, List defaultValue) {
this(propName, defaultValue, DEFAULT_DELIMITER);
}
/**
* Create the dynamic list property. The guava Splitter used is created as
* Splitter.onPattern(delimiterRegex).omitEmptyStrings().trimResults(). The default
* list value will be taken from the passed in list argument.
*/
public DynamicListProperty(String propName, List defaultValue, String delimiterRegex) {
setup(propName, defaultValue, delimiterRegex);
}
/**
* Create the dynamic list property using the splitter and default list value passed in
* from the arguments.
*/
public DynamicListProperty(String propName, List defaultValue, Splitter splitter) {
setup(propName, defaultValue, splitter);
}
private void setup(String propName, List defaultValue, String delimiterRegex) {
setup(propName, defaultValue, Splitter.onPattern(delimiterRegex).omitEmptyStrings().trimResults());
}
private void setup(String propName, List defaultValue, Splitter splitter) {
// Make a defensive copy of the default value. Would prefer to use an ImmutableList, but that
// does not allow for null values in the List.
this.defaultValues = (defaultValue == null ? null :
Collections.unmodifiableList(new ArrayList(defaultValue)));
this.splitter = splitter;
delegate = DynamicPropertyFactory.getInstance().getStringProperty(propName, null);
load();
Runnable callback = new Runnable() {
@Override
public void run() {
propertyChangedInternal();
}
};
delegate.addCallback(callback);
}
private void propertyChangedInternal() {
load();
propertyChanged();
}
/**
* A method invoked when the underlying string property is changed. Default implementation does nothing.
* Subclass can override this method
* to receive callback.
*/
protected void propertyChanged() {
}
/**
* Get the list type from the underlying dynamic string property. If the property is undefined, this method
* returns the default list value.
*/
public List get() {
return values;
}
@Override
public List getValue() {
return get();
}
@Override
public List getDefaultValue() {
return defaultValues;
}
private List split(String value) {
return Lists.newArrayList(splitter.split(Strings.nullToEmpty(value)));
}
protected List transform(List stringValues) {
List list = new ArrayList(stringValues.size());
for (String s : stringValues) {
list.add(from(s));
}
return Collections.unmodifiableList(list);
}
protected void load() {
if (delegate.get() == null) {
values = defaultValues;
} else {
values = transform(split(delegate.get()));
}
}
/**
* Gets the time (in milliseconds past the epoch) when the property
* was last set/changed.
*/
@Override
public long getChangedTimestamp() {
return delegate.getChangedTimestamp();
}
/**
* Add the callback to be triggered when the value of the property is changed
*
*/
@Override
public void addCallback(Runnable callback) {
if (callback != null) {
delegate.addCallback(callback);
}
}
/**
* Remove all callbacks registered through this instance of property
*/
@Override
public void removeAllCallbacks() {
delegate.removeAllCallbacks();
}
/**
* Construct the generic type from string.
*
*/
protected abstract T from(String value);
/**
* Getter for the property name
*/
@Override
public String getName() {
return delegate.getName();
}
}
