eed090e5f5
Prior to this change, request-scoped components having
@Resource-injected dependencies caused a memory leak in
DefaultListableBeanFactory#dependenciesForBeanMap.
Consider the following example:
@Component
@Scope(value="request", proxyMode=ScopedProxyMode.TARGET_CLASS)
public class MyComponent {
@Resource
private HttpServletRequest request;
// ...
}
The bean name for "MyComponent" will end up being
'scopedTarget.myComponent', which will become a key in
the #dependenciesForBeanMap structure.
On the first request, the injected HttpServletRequest bean will be a
proxy and will internally have a bean name of the form
"$Proxy10@1a3a2a52". This name will be added to the Set value associated
with the 'scopedTarget.myComponent' entry in #dependenciesForBeanMap.
On the second request, the process will repeat, but the injected
HttpServletRequest will be a different proxy instance, thus having a
different identity hex string, e.g. "$Proxy10@5eba06ff". This name will
also be added to the Set value associated with the
'scopedTarget.myComponent' entry in #dependenciesForBeanMap, and this
is the source of the leak: a new entry is added to the set on each
request but should be added only once.
This commit fixes the leak by introducing caching to
CommonAnnotationBeanPostProcessor#ResourceElement similar to that already
present in AutowiredAnnotationBeanPostProcessor#AutowiredFieldElement
and #AutowiredMethodElement. Essentially, each ResourceElement instance
now tracks whether it has been created, caches the ultimate value to be
injected and returns it eagerly if necessary. Besides solving the memory
leak, this has the side effect of avoiding unnecessary proxy creation.
This fix also explains clearly why injection into request-scoped
components using @Autowired never suffered this memory leak: because the
correct caching was already in place. Because @Resource is considerably
less-frequently used than @Autowired, and given that this particular
injection arrangement is relatively infrequent, it becomes
understandable how this bug has been present without being reported
since the introduction of @Resource support in Spring 2.5: developers
were unlikely to encounter it in the first place; and if they did, the
leak was minor enough (adding strings to a Set), that it could
potentially go unnoticed indefinitely depending on request volumes and
available memory.
Issue: SPR-9363
Backport-Issue: SPR-9176
Backport-Commit: f779c199ea
Spring Framework
The Spring Framework provides a comprehensive programming and configuration model for modern Java-based enterprise applications - on any kind of deployment platform. A key element of Spring is infrastructural support at the application level: Spring focuses on the "plumbing" of enterprise applications so that teams can focus on application-level business logic, without unnecessary ties to specific deployment environments.
The framework also serves as the foundation for Spring Integration, Spring Batch and the rest of the Spring family of projects. Browse the repositories under the SpringSource organization on GitHub for a full list.
.NET and Python variants are available as well.
Downloading artifacts
Instructions on downloading Spring artifacts via Maven and other build systems are available via the project wiki.
Documentation
See the current Javadoc and Reference docs.
Getting support
Check out the Spring forums and the Spring tag on StackOverflow. Commercial support is available too.
Issue Tracking
Spring's JIRA issue tracker can be found here. Think you've found a bug? Please consider submitting a reproduction project via the spring-framework-issues repository. The readme provides simple step-by-step instructions.
Building from source
Instructions on building Spring from source are available via the project wiki.
Contributing
Pull requests are welcome; you'll be asked to sign our contributor license agreement (CLA). Trivial changes like typo fixes are especially appreciated (just fork and edit!). For larger changes, please search through JIRA for similiar issues, creating a new one if necessary, and discuss your ideas with the Spring team.
Staying in touch
Follow @springframework and its team members on Twitter. In-depth articles can be found at the SpringSource team blog, and releases are announced via our news feed.
License
The Spring Framework is released under version 2.0 of the Apache License.