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/*
 * Copyright 2002-2020 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
 *
 *      https://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.web.util;

import javax.servlet.ServletContext;

import org.springframework.lang.Nullable;
import org.springframework.util.PropertyPlaceholderHelper;
import org.springframework.util.SystemPropertyUtils;

/**
 * Helper class for resolving placeholders in texts. Usually applied to file paths.
 *
 * 

A text may contain {@code ${...}} placeholders, to be resolved as servlet context * init parameters or system properties: e.g. {@code ${user.dir}}. Default values can * be supplied using the ":" separator between key and value. * * @author Juergen Hoeller * @author Marten Deinum * @since 3.2.2 * @see SystemPropertyUtils * @see ServletContext#getInitParameter(String) */ public abstract class ServletContextPropertyUtils { private static final PropertyPlaceholderHelper strictHelper = new PropertyPlaceholderHelper(SystemPropertyUtils.PLACEHOLDER_PREFIX, SystemPropertyUtils.PLACEHOLDER_SUFFIX, SystemPropertyUtils.VALUE_SEPARATOR, false); private static final PropertyPlaceholderHelper nonStrictHelper = new PropertyPlaceholderHelper(SystemPropertyUtils.PLACEHOLDER_PREFIX, SystemPropertyUtils.PLACEHOLDER_SUFFIX, SystemPropertyUtils.VALUE_SEPARATOR, true); /** * Resolve ${...} placeholders in the given text, replacing them with corresponding * servlet context init parameter or system property values. * @param text the String to resolve * @param servletContext the servletContext to use for lookups. * @return the resolved String * @throws IllegalArgumentException if there is an unresolvable placeholder * @see SystemPropertyUtils#PLACEHOLDER_PREFIX * @see SystemPropertyUtils#PLACEHOLDER_SUFFIX * @see SystemPropertyUtils#resolvePlaceholders(String, boolean) */ public static String resolvePlaceholders(String text, ServletContext servletContext) { return resolvePlaceholders(text, servletContext, false); } /** * Resolve ${...} placeholders in the given text, replacing them with corresponding * servlet context init parameter or system property values. Unresolvable placeholders * with no default value are ignored and passed through unchanged if the flag is set to true. * @param text the String to resolve * @param servletContext the servletContext to use for lookups. * @param ignoreUnresolvablePlaceholders flag to determine is unresolved placeholders are ignored * @return the resolved String * @throws IllegalArgumentException if there is an unresolvable placeholder and the flag is {@code false} * @see SystemPropertyUtils#PLACEHOLDER_PREFIX * @see SystemPropertyUtils#PLACEHOLDER_SUFFIX * @see SystemPropertyUtils#resolvePlaceholders(String, boolean) */ public static String resolvePlaceholders( String text, ServletContext servletContext, boolean ignoreUnresolvablePlaceholders) { if (text.isEmpty()) { return text; } PropertyPlaceholderHelper helper = (ignoreUnresolvablePlaceholders ? nonStrictHelper : strictHelper); return helper.replacePlaceholders(text, new ServletContextPlaceholderResolver(text, servletContext)); } private static class ServletContextPlaceholderResolver implements PropertyPlaceholderHelper.PlaceholderResolver { private final String text; private final ServletContext servletContext; public ServletContextPlaceholderResolver(String text, ServletContext servletContext) { this.text = text; this.servletContext = servletContext; } @Override @Nullable public String resolvePlaceholder(String placeholderName) { try { String propVal = this.servletContext.getInitParameter(placeholderName); if (propVal == null) { // Fall back to system properties. propVal = System.getProperty(placeholderName); if (propVal == null) { // Fall back to searching the system environment. propVal = System.getenv(placeholderName); } } return propVal; } catch (Throwable ex) { System.err.println("Could not resolve placeholder '" + placeholderName + "' in [" + this.text + "] as ServletContext init-parameter or system property: " + ex); return null; } } } }





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