com.avaje.ebean.config.PropertyExpression Maven / Gradle / Ivy
package com.avaje.ebean.config;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import javax.naming.InitialContext;
import javax.naming.NamingException;
/**
* Helper used to evaluate expressions such as ${CATALINA_HOME}.
*
* The expressions can contain environment variables, system properties or JNDI
* properties. JNDI expressions take the form ${jndi:propertyName} where you
* substitute propertyName with the name of the jndi property you wish to
* evaluate.
*
*/
final class PropertyExpression {
private static final Logger logger = LoggerFactory.getLogger(PropertyExpression.class);
/**
* Prefix for looking up JNDI Environment variable.
*/
private static final String JAVA_COMP_ENV = "java:comp/env/";
/**
* Used to detect the start of an expression.
*/
private static final String START = "${";
/**
* Used to detect the end of an expression.
*/
private static final String END = "}";
/**
* Specify the PropertyHolder.
*/
private PropertyExpression() {
}
/**
* Return the property value evaluating and replacing any expressions such as
* ${CATALINA_HOME}.
*/
static String eval(String val, PropertyMap map) {
if (val == null) {
return null;
}
int sp = val.indexOf(START);
if (sp > -1) {
int ep = val.indexOf(END, sp + 1);
if (ep > -1) {
return eval(val, sp, ep, map);
}
}
return val;
}
/**
* Convert the expression using JNDI, Environment variables, System Properties
* or existing an property in SystemProperties itself.
*/
private static String evaluateExpression(String exp, PropertyMap map) {
if (isJndiExpression(exp)) {
// JNDI property lookup...
String val = getJndiProperty(exp);
if (val != null) {
return val;
}
}
// check Environment Variables first
String val = System.getenv(exp);
if (val == null) {
// then check system properties
val = System.getProperty(exp);
}
if (val == null && map != null) {
// then check PropertyMap
val = map.get(exp);
}
if (val != null) {
return val;
} else {
// unable to evaluate yet... but maybe later based on the order
// in which properties are being set/loaded. You can use
// GlobalProperties.evaluateExpressions() to get any unresolved
// expressions to be evaluated
logger.debug("Unable to evaluate expression [" + exp + "]");
return null;
}
}
private static String eval(String val, int sp, int ep, PropertyMap map) {
StringBuilder sb = new StringBuilder();
sb.append(val.substring(0, sp));
String cal = evalExpression(val, sp, ep, map);
sb.append(cal);
eval(val, ep + 1, sb, map);
return sb.toString();
}
private static void eval(String val, int startPos, StringBuilder sb, PropertyMap map) {
if (startPos < val.length()) {
int sp = val.indexOf(START, startPos);
if (sp > -1) {
// append what is between the last token and the new one (if startPos ==
// sp nothing gets added)
sb.append(val.substring(startPos, sp));
int ep = val.indexOf(END, sp + 1);
if (ep > -1) {
String cal = evalExpression(val, sp, ep, map);
sb.append(cal);
eval(val, ep + 1, sb, map);
return;
}
}
}
// append what is left...
sb.append(val.substring(startPos));
}
private static String evalExpression(String val, int sp, int ep, PropertyMap map) {
// trim off start and end ${ and }
String exp = val.substring(sp + START.length(), ep);
// evaluate the variable
String evaled = evaluateExpression(exp, map);
if (evaled != null) {
return evaled;
} else {
// unable to evaluate at this stage (maybe later)
return START + exp + END;
}
}
private static boolean isJndiExpression(String exp) {
return exp.startsWith("JNDI:") || exp.startsWith("jndi:");
}
/**
* Returns null if JNDI is not setup or if the property is not found.
*
* @param key
* the key of the JNDI Environment property including a JNDI: prefix.
*/
private static String getJndiProperty(String key) {
try {
// remove the JNDI: prefix
key = key.substring(5);
return (String) getJndiObject(key);
} catch (NamingException ex) {
return null;
}
}
/**
* Similar to getProperty but throws NamingException if JNDI is not setup or
* if the property is not found.
*/
private static Object getJndiObject(String key) throws NamingException {
InitialContext ctx = new InitialContext();
return ctx.lookup(JAVA_COMP_ENV + key);
}
}