io.joshworks.snappy.loader.util.SystemPropertyUtils Maven / Gradle / Ivy
/*
* Copyright 2012-2015 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 io.joshworks.snappy.loader.util;
import java.util.HashSet;
import java.util.Properties;
import java.util.Set;
/**
* Helper class for resolving placeholders in texts. Usually applied to file paths.
*
* A text may contain {@code $ ...} placeholders, to be resolved as system properties:
* e.g. {@code $ user.dir} . Default values can be supplied using the ":" separator
* between key and value.
*
* Adapted from Spring.
*
* @author Juergen Hoeller
* @author Rob Harrop
* @author Dave Syer
* @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 = "}";
/**
* Value separator for system property placeholders: ":".
*/
public static final String VALUE_SEPARATOR = ":";
private static final String SIMPLE_PREFIX = PLACEHOLDER_PREFIX.substring(1);
/**
* Resolve ${...} placeholders in the given text, replacing them with corresponding
* system property values.
*
* @param text the String to resolve
* @return the resolved String
* @throws IllegalArgumentException if there is an unresolvable placeholder
* @see #PLACEHOLDER_PREFIX
* @see #PLACEHOLDER_SUFFIX
*/
public static String resolvePlaceholders(String text) {
if (text == null) {
return text;
}
return parseStringValue(null, text, text, new HashSet());
}
/**
* Resolve ${...} placeholders in the given text, replacing them with corresponding
* system property values.
*
* @param properties a properties instance to use in addition to System
* @param text the String to resolve
* @return the resolved String
* @throws IllegalArgumentException if there is an unresolvable placeholder
* @see #PLACEHOLDER_PREFIX
* @see #PLACEHOLDER_SUFFIX
*/
public static String resolvePlaceholders(Properties properties, String text) {
if (text == null) {
return text;
}
return parseStringValue(properties, text, text, new HashSet());
}
private static String parseStringValue(Properties properties, String value,
String current, Set visitedPlaceholders) {
StringBuilder buf = new StringBuilder(current);
int startIndex = current.indexOf(PLACEHOLDER_PREFIX);
while (startIndex != -1) {
int endIndex = findPlaceholderEndIndex(buf, startIndex);
if (endIndex != -1) {
String placeholder = buf
.substring(startIndex + PLACEHOLDER_PREFIX.length(), endIndex);
String originalPlaceholder = placeholder;
if (!visitedPlaceholders.add(originalPlaceholder)) {
throw new IllegalArgumentException("Circular placeholder reference '"
+ originalPlaceholder + "' in property definitions");
}
// Recursive invocation, parsing placeholders contained in the
// placeholder
// key.
placeholder = parseStringValue(properties, value, placeholder,
visitedPlaceholders);
// Now obtain the value for the fully resolved key...
String propVal = resolvePlaceholder(properties, value, placeholder);
if (propVal == null && VALUE_SEPARATOR != null) {
int separatorIndex = placeholder.indexOf(VALUE_SEPARATOR);
if (separatorIndex != -1) {
String actualPlaceholder = placeholder.substring(0,
separatorIndex);
String defaultValue = placeholder
.substring(separatorIndex + VALUE_SEPARATOR.length());
propVal = resolvePlaceholder(properties, value,
actualPlaceholder);
if (propVal == null) {
propVal = defaultValue;
}
}
}
if (propVal != null) {
// Recursive invocation, parsing placeholders contained in the
// previously resolved placeholder value.
propVal = parseStringValue(properties, value, propVal,
visitedPlaceholders);
buf.replace(startIndex, endIndex + PLACEHOLDER_SUFFIX.length(),
propVal);
startIndex = buf.indexOf(PLACEHOLDER_PREFIX,
startIndex + propVal.length());
} else {
// Proceed with unprocessed value.
startIndex = buf.indexOf(PLACEHOLDER_PREFIX,
endIndex + PLACEHOLDER_SUFFIX.length());
}
visitedPlaceholders.remove(originalPlaceholder);
} else {
startIndex = -1;
}
}
return buf.toString();
}
private static String resolvePlaceholder(Properties properties, String text,
String placeholderName) {
String propVal = getProperty(placeholderName, null, text);
if (propVal != null) {
return propVal;
}
return properties == null ? null : properties.getProperty(placeholderName);
}
public static String getProperty(String key) {
return getProperty(key, null, "");
}
public static String getProperty(String key, String defaultValue) {
return getProperty(key, defaultValue, "");
}
/**
* Search the System properties and environment variables for a value with the
* provided key. Environment variables in {@code UPPER_CASE} style are allowed where
* System properties would normally be {@code lower.case}.
*
* @param key the key to resolve
* @param defaultValue the default value
* @param text optional extra context for an error message if the key resolution fails
* (e.g. if System properties are not accessible)
* @return a static property value or null of not found
*/
public static String getProperty(String key, String defaultValue, String text) {
try {
String propVal = System.getProperty(key);
if (propVal == null) {
// Fall back to searching the system environment.
propVal = System.getenv(key);
}
if (propVal == null) {
// Try with underscores.
propVal = System.getenv(key.replace(".", "_"));
}
if (propVal == null) {
// Try uppercase with underscores as well.
propVal = System.getenv(key.toUpperCase().replace(".", "_"));
}
if (propVal != null) {
return propVal;
}
} catch (Throwable ex) {
System.err.println("Could not resolve key '" + key + "' in '" + text
+ "' as system property or in environment: " + ex);
}
return defaultValue;
}
private static int findPlaceholderEndIndex(CharSequence buf, int startIndex) {
int index = startIndex + PLACEHOLDER_PREFIX.length();
int withinNestedPlaceholder = 0;
while (index < buf.length()) {
if (substringMatch(buf, index, PLACEHOLDER_SUFFIX)) {
if (withinNestedPlaceholder > 0) {
withinNestedPlaceholder--;
index = index + PLACEHOLDER_SUFFIX.length();
} else {
return index;
}
} else if (substringMatch(buf, index, SIMPLE_PREFIX)) {
withinNestedPlaceholder++;
index = index + SIMPLE_PREFIX.length();
} else {
index++;
}
}
return -1;
}
private static boolean substringMatch(CharSequence str, int index,
CharSequence substring) {
for (int j = 0; j < substring.length(); j++) {
int i = index + j;
if (i >= str.length() || str.charAt(i) != substring.charAt(j)) {
return false;
}
}
return true;
}
}