路径字符替换（来自Spring源码）

/** * Abstract base class for PropertyEditors that need * to resolve placeholders in paths. * * <p>A path may contain ${...} placeholders, to be resolved as * system properties: e.g. ${user.dir}. * * @author Juergen Hoeller * @since 1.1.2 * @see #PLACEHOLDER_PREFIX * @see #PLACEHOLDER_SUFFIX * @see System#getProperty(String) */public class AbstractPathResolvingPropertyEditor extends PropertyEditorSupport {public static final String PLACEHOLDER_PREFIX = "${";public static final String PLACEHOLDER_SUFFIX = "}";protected static final Log logger = LogFactory.getLog(AbstractPathResolvingPropertyEditor.class);/** * Resolve the given path, replacing ${...} placeholders with * corresponding system property values if necessary. * @param path the original file path * @return the resolved file path * @see #PLACEHOLDER_PREFIX * @see #PLACEHOLDER_SUFFIX */    protected String resolvePath(String path) {StringBuilder buf = new StringBuilder(path);// The following code does not use JDK 1.4's StringBuffer.indexOf(String)// method to retain JDK 1.3 compatibility. The slight loss in performance// is not really relevant, as this code will typically just run on startup.int startIndex = path.indexOf(PLACEHOLDER_PREFIX);while (startIndex != -1) {int endIndex = buf.toString().indexOf(PLACEHOLDER_SUFFIX, startIndex + PLACEHOLDER_PREFIX.length());if (endIndex != -1) {String placeholder = buf.substring(startIndex + PLACEHOLDER_PREFIX.length(), endIndex);String propVal = System.getProperty(placeholder);if (propVal != null) {buf.replace(startIndex, endIndex + PLACEHOLDER_SUFFIX.length(), propVal);startIndex = buf.toString().indexOf(PLACEHOLDER_PREFIX, startIndex + propVal.length());} else {logger.warn("Could not resolve placeholder '" + placeholder + "' in resource path [" + path + "] as system property");startIndex = buf.toString().indexOf(PLACEHOLDER_PREFIX, endIndex + PLACEHOLDER_SUFFIX.length());}} else {startIndex = -1;}}return buf.toString();}}