spring 学习1-Request, session, and global session scopes|（Initial web configuration）

Initial web configuration

To support the scoping of beans at the

request

,

session

,
and

global session

levels
(web-scoped beans), some minor initial configuration is required before you define your beans. (This initial setup is not required for the standard scopes, singleton and prototype.)

How you accomplish this initial setup depends on your particular Servlet environment..

If you access scoped beans within Spring Web MVC, in effect, within a request that is processed by the Spring

DispatcherServlet

,
or

DispatcherPortlet

,
then no special setup is necessary:

DispatcherServlet

and

DispatcherPortlet

already
expose all relevant state.

If you use a Servlet 2.5 web container, with requests processed outside of Spring’s DispatcherServlet (for example, when using JSF or Struts), you need to register the

org.springframework.web.context.request.RequestContextListener

ServletRequestListener

.
For Servlet 3.0+, this can done programmatically via the

WebApplicationInitializer

interface.
Alternatively, or for older containers, add the following declaration to your web application’s

web.xml

file:

<web-app>
...
<listener>
<listener-class>
org.springframework.web.context.request.RequestContextListener
</listener-class>
</listener>
...
</web-app>

Alternatively, if there are issues with your listener setup, consider the provided

RequestContextFilter

.
The filter mapping depends on the surrounding web application configuration, so you have to change it as appropriate.

<web-app>
...
<filter>
<filter-name>requestContextFilter</filter-name>
<filter-class>org.springframework.web.filter.RequestContextFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>requestContextFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
...
</web-app>

DispatcherServlet

,

RequestContextListener

and

RequestContextFilter

all
do exactly the same thing, namely bind the HTTP request object to the

Thread

that
is servicing that request. This makes beans that are request- and session-scoped available further down the call chain.