org.jboss.dmr.ValueExpressionResolver Maven / Gradle / Ivy
/*
* JBoss, Home of Professional Open Source.
* Copyright 2013, 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.dmr;
import java.io.File;
/**
* A resolver for value expressions.
*
* @author David M. Lloyd
*/
public class ValueExpressionResolver {
/**
* The default value expression resolver.
*/
public static final ValueExpressionResolver DEFAULT_RESOLVER = new ValueExpressionResolver();
/**
* Construct a new instance.
*/
public ValueExpressionResolver() {
}
/**
* Perform expression resolution.
*
* @param expression the expression to resolve
* @return the resolved string
*/
public String resolve(ValueExpression expression) {
final String value = expression.getExpressionString();
final StringBuilder builder = new StringBuilder();
final int len = value.length();
int state = INITIAL;
int start = -1;
int nest = 0;
int nameStart = -1;
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('$').appendCodePoint(ch);
state = INITIAL;
continue;
}
}
// not reachable
}
case GOT_OPEN_BRACE: {
switch (ch) {
case '{': {
nest++;
continue;
}
case ':':
if (nameStart == i) {
// not a default delimiter; same as default case
continue;
}
// else fall into the logic for 'end of key to resolve cases' "," and "}"
case '}':
case ',': {
if (nest > 0) {
if (ch == '}') nest--;
continue;
}
final String val = resolvePart(value.substring(nameStart, i).trim());
if (val != null && !val.equals(value)) {
builder.append(val);
state = ch == '}' ? INITIAL : RESOLVED;
continue;
} else if (ch == ',') {
nameStart = i + 1;
continue;
} else if (ch == ':') {
start = i + 1;
state = DEFAULT;
continue;
} else {
throw new IllegalStateException("Failed to resolve expression: "+ value.substring(start - 2, i + 1));
}
}
default: {
continue;
}
}
// not reachable
}
case RESOLVED: {
if (ch == '{') {
nest ++;
} else if (ch == '}') {
if (nest > 0) {
nest--;
} else {
state = INITIAL;
}
}
continue;
}
case DEFAULT: {
if (ch == '{') {
nest ++;
} else if (ch == '}') {
if (nest > 0) {
nest --;
} else {
state = INITIAL;
builder.append(value.substring(start, i));
}
}
continue;
}
default:
throw new IllegalStateException("Unexpected char seen: "+ch);
}
}
switch (state) {
case GOT_DOLLAR: {
builder.append('$');
break;
}
case DEFAULT: {
builder.append(value.substring(start - 2));
break;
}
case GOT_OPEN_BRACE: {
// We had a reference that was not resolved, throw ISE
throw new IllegalStateException("Incomplete expression: "+builder.toString());
}
}
return builder.toString();
}
/**
* Resolve a single name in the expression. Return {@code null} if no resolution is possible. The default
* implementation (which may be delegated to) checks system properties, environment variables, and a small set of
* special strings.
*
* @param name the name to resolve
* @return the resolved value, or {@code null} for none
*/
protected String resolvePart(String name) {
if ("/".equals(name)) {
return File.separator;
} else if (":".equals(name)) {
return File.pathSeparator;
}
// 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));
return val;
}
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;
}
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