public void registerEvaluator(ExpressionEvaluator evaluator) {
if (evaluator == null) {
throw new IllegalArgumentException(CoreMessages.objectIsNull("evaluator").getMessage());
}
final String name = evaluator.getName();
// TODO MULE-3809 Eliminate duplicate evaluators registration
if (logger.isDebugEnabled()) {
logger.debug(
"Evaluators already contain an object named '"
+ name
+ "'. The previous object will be overwritten.");
}
evaluators.put(evaluator.getName(), evaluator);
}
/**
* Evaluates the given expression. The expression should be a single expression definition with or
* without enclosing braces. i.e. "mule:serviceName" and "#[mule:serviceName]" are both valid. For
* situations where one or more expressions need to be parsed within a single text, the {@link
* org.mule.api.expression.ExpressionManager#parse(String,org.mule.api.MuleMessage,boolean)}
* method should be used since it will iterate through all expressions in a string.
*
* @param expression a single expression i.e. xpath://foo
* @param evaluator the evaluator to use when executing the expression
* @param message the current message to process. The expression will evaluata on the message.
* @param failIfNull determines if an exception should be thrown if expression could not be
* evaluated or returns null or if an exception should be thrown if an empty collection is
* returned.
* @return the result of the evaluation. Expressions that return collection will return an empty
* collection, not null.
* @throws ExpressionRuntimeException if the expression is invalid, or a null is found for the
* expression and 'failIfNull is set to true.
*/
public Object evaluate(
String expression, String evaluator, MuleMessage message, boolean failIfNull)
throws ExpressionRuntimeException {
ExpressionEvaluator extractor = (ExpressionEvaluator) evaluators.get(evaluator);
if (extractor == null) {
throw new IllegalArgumentException(
CoreMessages.expressionEvaluatorNotRegistered(evaluator).getMessage());
}
Object result = extractor.evaluate(expression, message);
// TODO Handle empty collections || (result instanceof Collection &&
// ((Collection)result).size()==0)
if (failIfNull && (result == null)) {
throw new ExpressionRuntimeException(
CoreMessages.expressionEvaluatorReturnedNull(evaluator, expression));
}
if (logger.isDebugEnabled()) {
logger.debug(
MessageFormat.format(
"Result of expression: {0}:{1} is: {2}", evaluator, expression, result));
}
return result;
}