You can configure whether a modified JSP gets compiled or not in the default-web.xml file. This file can be found in the config directory of your domain.
The initialization parameter "development" of the JspServlet must be set to "debug". This is the default value for a developer profile.
To be on the safe side you might wish to add the following lines to your JSP-servlet:
<init-param>
<param-name>development</param-name>
<param-value>true</param-value>
</init-param>
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