Self injection with Spring

Update: February 2016

Self autowiring will be officially supported in Spring Framework 4.3. The implementation can be seen in this GitHub commit.

The definitive reason that you cannot autowire yourself is that the implementation of Spring's DefaultListableBeanFactory.findAutowireCandidates(String, Class, DependencyDescriptor) method explicitly excludes the possibility. This is visible in the following code excerpt from this method:

for (String candidateName : candidateNames) {    if (!candidateName.equals(beanName) && isAutowireCandidate(candidateName, descriptor)) {        result.put(candidateName, getBean(candidateName));    }}

FYI: the name of the bean (i.e., the bean that's trying to autowire itself) is beanName. That bean is in fact an autowire candidate, but the above if-condition returns false (since candidateName in fact equals the beanName). Thus you simply cannot autowire a bean with itself (at least not as of Spring 3.1 M1).

Now as for whether or not this is intended behavior semantically speaking, that's another question. ;)

I'll ask Juergen and see what he has to say.

Regards,

Sam (Core Spring Committer)

p.s. I've opened a Spring JIRA issue to consider supporting self-autowiring by type using @Autowired. Feel free to watch or vote for this issue here: https://jira.springsource.org/browse/SPR-8450

This code works too:

@Servicepublic class UserService implements Service {    @Autowired    private ApplicationContext applicationContext;    private Service self;    @PostConstruct    private void init() {        self = applicationContext.getBean(UserService.class);    }}

I don't know why, but it seems that Spring can get the bean from ApplicationContext if is created, but not initialized. @Autowired works before initialization and it cannot find the same bean. So, @Resource maybe works after @Autowired and before @PostConstruct.

But I don't know, just speculating. Anyway, good question.

By the way, the more elegant solution to the self-invocation problem is to use AspectJ Load-Time Weaving for your transactional proxies (or whatever AOP-introduced proxy you're using).

For example, with annotation-driven transaction management, you can use the "aspectj" mode as follows:

<tx:annotation-driven mode="aspectj" />

Note that the default mode is "proxy" (i.e., JDK dynamic proxies).

Regards,

Sam