Spring Framework example source code file (SystemPropertyUtils.java)

This example Spring Framework source code file (SystemPropertyUtils.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

could, could, log, placeholder_prefix, placeholder_prefix, placeholder_suffix, string, string, stringbuffer, stringbuffer, systempropertyutils, throwable

The Spring Framework SystemPropertyUtils.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.util;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Helper class for resolving placeholders in texts. Usually applied to file paths.
 *
 * <p>A text may contain ${...} placeholders, to be resolved as
 * system properties: e.g. <code>${user.dir}.
 *
 * @author Juergen Hoeller
 * @since 1.2.5
 * @see #PLACEHOLDER_PREFIX
 * @see #PLACEHOLDER_SUFFIX
 * @see System#getProperty(String)
 */
public abstract class SystemPropertyUtils {

	/** Prefix for system property placeholders: "${" */
	public static final String PLACEHOLDER_PREFIX = "${";

	/** Suffix for system property placeholders: "}" */
	public static final String PLACEHOLDER_SUFFIX = "}";

	private static final Log logger = LogFactory.getLog(SystemPropertyUtils.class);


	/**
	 * Resolve ${...} placeholders in the given text,
	 * replacing them with corresponding system property values.
	 * @param text the String to resolve
	 * @return the resolved String
	 * @see #PLACEHOLDER_PREFIX
	 * @see #PLACEHOLDER_SUFFIX
	 */
	public static String resolvePlaceholders(String text) {
		StringBuffer buf = new StringBuffer(text);

		int startIndex = buf.indexOf(PLACEHOLDER_PREFIX);
		while (startIndex != -1) {
			int endIndex = buf.indexOf(PLACEHOLDER_SUFFIX, startIndex + PLACEHOLDER_PREFIX.length());
			if (endIndex != -1) {
				String placeholder = buf.substring(startIndex + PLACEHOLDER_PREFIX.length(), endIndex);
				int nextIndex = endIndex + PLACEHOLDER_SUFFIX.length();
				try {
					String propVal = System.getProperty(placeholder);
					if (propVal == null) {
						// Fall back to searching the system environment.
						propVal = System.getenv(placeholder);
					}
					if (propVal != null) {
						buf.replace(startIndex, endIndex + PLACEHOLDER_SUFFIX.length(), propVal);
						nextIndex = startIndex + propVal.length();
					}
					else {
						if (logger.isWarnEnabled()) {
							logger.warn("Could not resolve placeholder '" + placeholder + "' in [" + text +
									"] as system property: neither system property nor environment variable found");
						}
					}
				}
				catch (Throwable ex) {
					if (logger.isWarnEnabled()) {
						logger.warn("Could not resolve placeholder '" + placeholder + "' in [" + text +
								"] as system property: " + ex);
					}
				}
				startIndex = buf.indexOf(PLACEHOLDER_PREFIX, nextIndex);
			}
			else {
				startIndex = -1;
			}
		}

		return buf.toString();
	}

}