Spring Framework example source code file (PreferencesPlaceholderConfigurer.java)

This example Spring Framework source code file (PreferencesPlaceholderConfigurer.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Spring Framework tags/keywords

backingstoreexception, beandefinitionstoreexception, cannot, initializingbean, initializingbean, preferences, preferences, preferencesplaceholderconfigurer, properties, propertyplaceholderconfigurer, propertyplaceholderconfigurer, string, string, util

The Spring Framework PreferencesPlaceholderConfigurer.java source code

/*
 * Copyright 2002-2007 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;

/**
 * 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 {

	private String systemTreePath;

	private String userTreePath;

	private Preferences systemPrefs;

	private Preferences userPrefs;


	/**
	 * 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.
	 */
	public void setUserTreePath(String userTreePath) {
		this.userTreePath = userTreePath;
	}


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

	/**
	 * This implementation tries to resolve placeholders as keys first
	 * in the user preferences, then in the system preferences, then in
	 * the passed-in properties.
	 */
	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.
	 * @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
	 */
	protected String resolvePlaceholder(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);
		}
	}

}