org.springframework.web.util.ServletContextPropertyUtils Maven / Gradle / Ivy
/*
* 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 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;
}
}
}
}