ImpalaWebConfiguration

Simple Startup

For vanilla Spring web applications, using a ContextLoader instance set up using a ContextLoaderListener in the web application's web.xml.

For Impala, the mechanisms is similar with a ContextLoaderListener subclass being used:

<listener>
    <listener-class>org.impalaframework.web.loader.ImpalaContextLoaderListener</listener-class>
</listener>

Impala startup works very similarly to regular Spring applications. The big difference is that the ContextLoader subclass does not bootstrap the application directly. Instead, it bootstraps the Impala runtime (itself just a set of Spring beans), which itself if responsible for loading the modules which comprise your application.

Advanced Startup

With Impala, it's straightforward to vary the ContextLoader subclass which is used to bootstrap Impala in a web environment. Simply add an extra entry into web.xml.

<context-param>
    <param-name>contextLoaderClassName</param-name>
    <param-value>my.context.loader.subclass.name</param-value>
</context-param>

If this element is not present, the default is assumed to be ExternalModuleContextLoader.

Changing the ContextLoader is appropriate if you want to modify the actual mechanism for bootstrapping Impala in a web application. If you are happy with this mechanism, but you want to vary the details of the Impala runtime configuration, then you have two choices:

• Using the built in configuration options.
• Setting or adding Spring XML configuration files (context locations) used to bootstrap Impala.