org.jboss.common.beans.property.PropertiesValueResolver Maven / Gradle / Ivy
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* JBoss, Home of Professional Open Source.
* Copyright 2011, Red Hat, Inc., and individual contributors
* as indicated by the @author tags. See the copyright.txt file in the
* distribution for a full listing of individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
package org.jboss.common.beans.property;
import java.io.File;
/**
* Parses a string and replaces any references to system properties or environment variables in the string
*
* @author Jaikiran Pai (copied from JBoss DMR project)
* @author David M. Lloyd
*/
public class PropertiesValueResolver {
private static final int INITIAL = 0;
private static final int GOT_DOLLAR = 1;
private static final int GOT_OPEN_BRACE = 2;
private static final int RESOLVED = 3;
private static final int DEFAULT = 4;
/**
* Replace properties of the form:
* ${<[env.]name>[,<[env.]name2>[,<[env.]name3>...]][:<default>]}
* Method inspects given string and replaces all encountered properties. If method is able to replace all properties, it
* returns String with replaced values. If it fails to replace property and ${} does not contain default declaration, method throws {@link IllegalStateException}.
*
* Example1:
*
* String toReplace = "userLang=${user.language};user=${env.USER}";
* String result = "userLang=en;user=santa";
*
*
* Example2:
*
* String toReplace = "userLang=${IDoneExist,user.language};user=${ImNotThereEither,env.USER}";
* String result = "userLang=en;user=santa";
*
*
* Example3:
*
* String toReplace = "userLang=${IDoneExist:user.language};user=${ImNotThereEither,env.USER:defaultWontBeUsed}";
* String result = "userLang=user.language;user=santa";
*
* NOTE: in Example 3 value of userLang in result String. The default value IS NOT RESOLVED. It is used as fallback value.
* @param value - string containig system or env variable reference(s)
* @return the value of the system property or environment variable referenced if it exists
* @throws IllegalStateException - thrown when state of properties does not allow to replace all variable references.
*/
public static String replaceProperties(final String value) throws IllegalStateException {
final StringBuilder builder = new StringBuilder();
final int len = value.length();
int state = INITIAL;
int start = -1;
int nameStart = -1;
String resolvedValue = null;
for (int i = 0; i < len; i = value.offsetByCodePoints(i, 1)) {
final int ch = value.codePointAt(i);
switch (state) {
case INITIAL: {
switch (ch) {
case '$': {
state = GOT_DOLLAR;
continue;
}
default: {
builder.appendCodePoint(ch);
continue;
}
}
// not reachable
}
case GOT_DOLLAR: {
switch (ch) {
case '$': {
builder.appendCodePoint(ch);
state = INITIAL;
continue;
}
case '{': {
start = i + 1;
nameStart = start;
state = GOT_OPEN_BRACE;
continue;
}
default: {
// invalid; emit and resume
builder.append('$').appendCodePoint(ch);
state = INITIAL;
continue;
}
}
// not reachable
}
case GOT_OPEN_BRACE: {
switch (ch) {
case ':':
case '}':
case ',': {
final String name = value.substring(nameStart, i).trim();
if ("/".equals(name)) {
builder.append(File.separator);
state = ch == '}' ? INITIAL : RESOLVED;
continue;
} else if (":".equals(name)) {
builder.append(File.pathSeparator);
state = ch == '}' ? INITIAL : RESOLVED;
continue;
}
// First check for system property, then env variable
String val = System.getProperty(name);
if (val == null && name.startsWith("env."))
val = System.getenv(name.substring(4));
if (val != null) {
builder.append(val);
resolvedValue = val;
state = ch == '}' ? INITIAL : RESOLVED;
continue;
} else if (ch == ',') {
nameStart = i + 1;
continue;
} else if (ch == ':') {
start = i + 1;
state = DEFAULT;
continue;
} else {
throw new IllegalStateException("Failed to resolve expression: "
+ value.substring(start - 2, i + 1));
}
}
default: {
continue;
}
}
// not reachable
}
case RESOLVED: {
if (ch == '}') {
state = INITIAL;
}
continue;
}
case DEFAULT: {
if (ch == '}') {
state = INITIAL;
builder.append(value.substring(start, i));
}
continue;
}
default:
throw new IllegalStateException("Unexpected char seen: " + ch);
}
}
switch (state) {
case GOT_DOLLAR: {
builder.append('$');
break;
}
case DEFAULT: {
builder.append(value.substring(start - 2));
break;
}
case GOT_OPEN_BRACE: {
// We had a reference that was not resolved, throw ISE
if (resolvedValue == null)
throw new IllegalStateException("Incomplete expression: " + builder.toString());
break;
}
}
return builder.toString();
}
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