Init-based application scope
When you need the "application" scoped beans, you need to access the ServletContext. But to access ServletContext through a HttpServletRequest, you need to pass through the HttpSession object! You maybe asked: why do I have to pass through a session to get the ServletContext, while the ServletContext exists from the start of the web application? And what do I do if I don't have any session? Do I have to create a new one?
With Scopes now you can use an "init-based" application scope, where the ServletContext is configured at start-up of the web application and without passing through a session object.
To use window scope see Using Scopes with "window" scope
What to put in "init-based" application scope
You can put everything you need to put in "normal" application scope, because it is the same object (ServletContext) that it is used!
Using Scopes with "init-based application" scope
To use the init-based "application" scope support in your web application you have to:
- extract the binary release;
- copy the "scopes.jar" file in the directory [webapp_root]/WEB-INF/lib;
- copy "lib/commons-io.jar" in [webapp_root]/WEB-INF/lib, or download the latest version from Jakarta Commons I/O site.
- configure the CompleteHttpScopesFilter in front of
your servlet, by modifying your "web.xml" file:
<filter> <filter-name>scopesFilter</filter-name> <filter-class>net.sourceforge.scopes.filters.CompleteScopesHttpFilter</filter-class> <init-param> <param-name>manager-scope-names</param-name> <param-value>request,session,application</param-value> </init-param> <init-param> <param-name>manager-class-names</param-name> <param-value> net.sourceforge.scopes.managers.impl.RequestScopeManager, net.sourceforge.scopes.managers.impl.SessionScopeManager, net.sourceforge.scopes.managers.impl.InitBasedApplicationScopeManager </param-value> </init-param> </filter> <filter-mapping> <filter-name>scopesFilter</filter-name> <servlet-name>myServletName</servlet-name> </filter-mapping>
- Installation finished! For the use see the Quick start
How "init-based" application scope works
When the Scopes filter is initialized, the "InitBasedApplicationScopeManager" takes the ServletContext from the FilterConfig object, using it for the rest of the execution.