In our hook that created a custom login action, we modified the
login.events.pre portal property. This property accepts multiple values, so our value was appended to the existing
login.events.pre values. We can repeatedly modify the property from additional hooks because it accepts multiple values. Some portal properties only accept a single value, such as the
terms.of.use.required property, which is either
false. Only modify single value properties from one hook; otherwise Liferay won’t know which value to use.
To find out which properties accept multiple values, look in the Configuring Liferay’s Properties document.
Now let’s look at overriding and adding Struts actions from a hook plugin.