[InternalResourceView] Allow exposeContextBeansAsAttributes to be applied to specific beans [SPR-4567]

[spring-projects-issues]

Kenny MacLeod opened SPR-4567 and commented

The exposeContextBeansAsAttributes property of InternalResourceView, while useful, is often a bit too wide-ranging in its effects. Sometimes you get a clash between bean names and JSP scoped variables which can be very hard to track down.

Could InternalResourceView be modified so that a specific collection of beans could be explicitly exposed as JSP attributes, rather than every one of them? These would be injected into the InternalResourceViewResolver by name or reference.

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Affects: 2.5.2

Issue Links:

• UrlBasedViewResolver should implement setExposedContextBeanNames (not InternalResourceViewResolver) [SPR-8064] #12719 UrlBasedViewResolver should implement setExposedContextBeanNames (not InternalResourceViewResolver)

[spring-projects-issues]

Juergen Hoeller commented

The "exposeContextBeansAsAttributes" feature is mainly intended for EL expressions in JSPs, allowing access to Spring beans by name (similar to JSF expressions and JSF-managed beans) - with explicit page/request-scoped attributes overriding those beans in case of overlapping names. What kind of clash did you experience there? Just unclearness where an attribute comes from, maybe in case of similar names?

For exposing specific beans to a set of views, consider setting InternalResourceViewResolver's "attributesMap" property, populating it with attribute names and attribute values that may be static values but may also be bean references (using <entry key="..." value-ref="...">). Note that this expects to refer to singleton beans; scoped beans or lazy-init beans cannot be exposed that way.

We could additionally consider an "exposedContextBeanNames" property, accepting a set of bean names to expose - only getting obtained when actually accessed through EL expressions (or through "request.getAttribute"). Is this what you have in mind?

Juergen

[spring-projects-issues]

Kenny MacLeod commented

That was the idea, yes. The use was that we had a legacy application with a large set of existing JSPs, which happened to be using their own page attributes whose names clashed with the names of the spring beans when the beans were exposed as JSP attributes. In this particular case, I only needed to expose a few spring beans, not all of them, and I could just have listed those beans names explicitly, it would have saved a lot of digging around looking for the duplicate names.

I couldn't have used the attributesMap property because, as you mentioned, some of them were scoped.

[spring-projects-issues]

Juergen Hoeller commented

I've added such a "exposedContextBeanNames" property to InternalResourceView(Resolver) for 2.5.3. Thanks for the suggestion!

Juergen