servletContext.setAttribute()

The servletContext.setAttribute() is dynamic which can be set and reset during runtime.

Where as init-parameter specified in web.xml is static which will not change during the lifetime of application.

Example:

• The database properties like database name configuration propety. It will be mostly configured as context init-param
• And if you want to set property value which derives based on runtime changes, like "last user logged in" or "number of failures" should be context attributes.