/*
 * Copyright 2002-2018 the original author or 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 org.springframework.beans.factory.config;

import java.util.Properties;
import java.util.prefs.BackingStoreException;
import java.util.prefs.Preferences;

import org.springframework.beans.factory.BeanDefinitionStoreException;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.lang.Nullable;

Subclass of PropertyPlaceholderConfigurer that supports JDK 1.4's Preferences API (java.util.prefs). 
Tries to resolve placeholders as keys first in the user preferences,
then in the system preferences, then in this configurer's properties.
Thus, behaves like PropertyPlaceholderConfigurer if no corresponding
preferences defined.
Supports custom paths for the system and user preferences trees. Also
supports custom paths specified in placeholders ("myPath/myPlaceholderKey").
Uses the respective root node if not specified.
Author:
Juergen Hoeller
See Also:
setSystemTreePath
setUserTreePath
Preferences
Since:
16.02.2004/**
 * Subclass of PropertyPlaceholderConfigurer that supports JDK 1.4's
 * Preferences API ({@code java.util.prefs}).
 *
 * <p>Tries to resolve placeholders as keys first in the user preferences,
 * then in the system preferences, then in this configurer's properties.
 * Thus, behaves like PropertyPlaceholderConfigurer if no corresponding
 * preferences defined.
 *
 * <p>Supports custom paths for the system and user preferences trees. Also
 * supports custom paths specified in placeholders ("myPath/myPlaceholderKey").
 * Uses the respective root node if not specified.
 *
 * @author Juergen Hoeller
 * @since 16.02.2004
 * @see #setSystemTreePath
 * @see #setUserTreePath
 * @see java.util.prefs.Preferences
 */
public class PreferencesPlaceholderConfigurer extends PropertyPlaceholderConfigurer implements InitializingBean {

	@Nullable
	private String systemTreePath;

	@Nullable
	private String userTreePath;

	private Preferences systemPrefs = Preferences.systemRoot();

	private Preferences userPrefs = Preferences.userRoot();


	
Set the path in the system preferences tree to use for resolving
placeholders. Default is the root node.
/**
	 * Set the path in the system preferences tree to use for resolving
	 * placeholders. Default is the root node.
	 */
	public void setSystemTreePath(String systemTreePath) {
		this.systemTreePath = systemTreePath;
	}

	
Set the path in the system preferences tree to use for resolving
placeholders. Default is the root node.
/**
	 * Set the path in the system preferences tree to use for resolving
	 * placeholders. Default is the root node.
	 */
	public void setUserTreePath(String userTreePath) {
		this.userTreePath = userTreePath;
	}


	
This implementation eagerly fetches the Preferences instances
for the required system and user tree nodes.
/**
	 * This implementation eagerly fetches the Preferences instances
	 * for the required system and user tree nodes.
	 */
	@Override
	public void afterPropertiesSet() {
		if (this.systemTreePath != null) {
			this.systemPrefs = this.systemPrefs.node(this.systemTreePath);
		}
		if (this.userTreePath != null) {
			this.userPrefs = this.userPrefs.node(this.userTreePath);
		}
	}

	
This implementation tries to resolve placeholders as keys first
in the user preferences, then in the system preferences, then in
the passed-in properties.
/**
	 * This implementation tries to resolve placeholders as keys first
	 * in the user preferences, then in the system preferences, then in
	 * the passed-in properties.
	 */
	@Override
	protected String resolvePlaceholder(String placeholder, Properties props) {
		String path = null;
		String key = placeholder;
		int endOfPath = placeholder.lastIndexOf('/');
		if (endOfPath != -1) {
			path = placeholder.substring(0, endOfPath);
			key = placeholder.substring(endOfPath + 1);
		}
		String value = resolvePlaceholder(path, key, this.userPrefs);
		if (value == null) {
			value = resolvePlaceholder(path, key, this.systemPrefs);
			if (value == null) {
				value = props.getProperty(placeholder);
			}
		}
		return value;
	}

	
Resolve the given path and key against the given Preferences.
Params:
path – the preferences path (placeholder part before '/')
key – the preferences key (placeholder part after '/')
preferences – the Preferences to resolve against
Returns:
the value for the placeholder, or null if none found/**
	 * Resolve the given path and key against the given Preferences.
	 * @param path the preferences path (placeholder part before '/')
	 * @param key the preferences key (placeholder part after '/')
	 * @param preferences the Preferences to resolve against
	 * @return the value for the placeholder, or {@code null} if none found
	 */
	@Nullable
	protected String resolvePlaceholder(@Nullable String path, String key, Preferences preferences) {
		if (path != null) {
			// Do not create the node if it does not exist...
			try {
				if (preferences.nodeExists(path)) {
					return preferences.node(path).get(key, null);
				}
				else {
					return null;
				}
			}
			catch (BackingStoreException ex) {
				throw new BeanDefinitionStoreException("Cannot access specified node path [" + path + "]", ex);
			}
		}
		else {
			return preferences.get(key, null);
		}
	}

}