Nucleus can configure a component from properties that are set in multiple configuration directories. If configuration files in multiple directories set the same property, Nucleus can resolve this in two ways:

Override property settings

You can override the settings in any properties file from another properties file that has higher precedence. For example, any settings in a module’s base configuration can be overridden by a properties file of the same name in the application’s localconfig directory.

Combine multi-value property settings

You can concatenate settings from multiple files for a given multi-value property (such as an array or list) by using the += operator, as follows:


Note: No white space should precede or follow the += operator.

This can be especially useful when you need to supplement existing settings that are supplied by the base configuration of an ATG module. For example, the standard ATG distribution provides the base, which starts a number of services:


It is likely that your application also starts its own set of services. Because installation of any later ATG distribution always overwrites the base, you should not modify this file so it includes application-specific services. You also should not override it with another copy of elsewhere in the configuration path—for example, in localconfig. If the next ATG distribution changes the installed list of initial services, those changes are shadowed by the localconfig version of

Instead, you can concatenate settings for the initialServices property from the base and localconfig versions of For example, you might modify localconfig/ as follows:


Given the previous settings in the base, this yields the following settings for initialServices:


By using the += operator, the store/CatalogManager entry is appended to the list of services already set by the base version of When Nucleus reads the configuration path, it finds two files in /config/config.jar and /localconfig, and combines initialServices settings from both files. If product updates change the base version’s set of services, the /localconfig setting is appended to the new set.

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