Do resource bundles in Java support runtime string substitution?

Question

Can you do the following with a Java ResourceBundle?

In the properties file...

example.dynamicresource=You currently have {0} accounts. 

At runtime...

int accountAcount = 3; bundle.get("example.dynamicresource",accountCount,param2,...); 

To give a result of

"You currently have 3 accounts."

Answer 1

Not without using the MessageFormat class, such as:

String pattern = bundle.getString("example.dynamicresource"); String message = MessageFormat.format(pattern, accountCount); 

Answer 2

On their own, ResourceBundle does not support property placeholders. The usual idea is to take the String you get from the bundle, and stick it into a MessageFormat, and then use that to get your parameterized message.

If you're using JSP/JSTL, then you can combine <fmt:message> and <fmt:param> to do this, which uses ResourceBundle and MessageFormat under the covers.

If you happen to be using Spring, then it has the ResourceBundleMessageSource which does something similar, and can be used anywhere in your program. This MessageSource abstraction (combined with MessageSourceAccessor) is much nicer to use than ResourceBundle.