列出由SpringMVC创建的请求范围和会话范围的bean

Question

If there's a list of these already available on the web, please link it. I couldn't find any such thing using the Googles.

Request-scoped beans:

• javax.servlet.http.HttpServletRequest

Session-scoped beans:

• javax.servlet.http.HttpSession

Answer 1

Autowiring happens once, after the object creation, and this is a main thing to keep in mind when reasoning about autowiring and different scopes.

About your question, there's in fact no issue when it comes to injecting longer living beans inside a short-lived beans. Its only important that you're aware of it and that it fits your semantic.

Other way around is a bit trickier. So injecting shorter lived beans, inside a longer lived beans. The proper way for doing this is leaning on proxies. If you're injecting a request-scoped bean inside a session-scoped bean, and if the request-scoped bean is proxied, than the proxy will be created only once, but will create a request bean on each request.

Its a simplification of what is described in the docs and available at http://docs.spring.io/spring/docs/current/spring-framework-reference/html/beans.html#beans-factory-scopes-other-injection

Answer 2

Well it really depends on what you've told Spring to create, but you'd see this in a default setup.

REQUEST:

    for(String key : Collections.list(request.getAttributeNames())) {
        System.out.println( key );
    }

RESULT:

org.springframework.web.context.request.async.WebAsyncManager.WEB_ASYNC_MANAGER
org.springframework.web.servlet.DispatcherServlet.CONTEXT
org.springframework.web.servlet.DispatcherServlet.LOCALE_RESOLVER
org.springframework.web.servlet.HandlerMapping.bestMatchingPattern
org.springframework.web.servlet.DispatcherServlet.OUTPUT_FLASH_MAP
org.springframework.web.servlet.DispatcherServlet.FLASH_MAP_MANAGER
org.springframework.core.convert.ConversionService
org.springframework.web.servlet.DispatcherServlet.THEME_SOURCE
org.springframework.web.servlet.HandlerMapping.pathWithinHandlerMapping
org.springframework.web.servlet.HandlerMapping.uriTemplateVariables
org.springframework.web.servlet.DispatcherServlet.THEME_RESOLVER

SESSION:

    for(String key : Collections.list(session.getAttributeNames())) {
        System.out.println( key );
    }

RESULT:

(empty)

Answer 3

You can autowire anything that Spring can build. Whether or not you should is another matter.

For example, it is utterly senseless to autowire a bean with Step scope (from batch processing) to a request scoped bean.