Spring Autowiring class vs. interface?

Question

I have this Spring config: ``` <bean id="boo" class="com.x.TheClass"/> ``` The class `TheClass` implements `TheInterface`. Then I have this (hypothetical) Java code: ``` @Autowired TheInterface x; @Autowired TheClass y; ``` The autowiring of `TheInterface` works but the autowiring of `TheClass` fails. Spring gives me a `NoSuchBeanDefinitionException` for the class. Why can you wire the interface and not the class?

Accepted Answer

Normally, both will work, you can autowire interfaces or classes.

There's probably an autoproxy generator somewhere in your context, which is wrapping your `boo` bean in a generated proxy object. This proxy object will implement `TheInterface`, but will not be a `TheClass`. When using autoproxies, you need to program to the interface, not the implementation.

The likely candidate is transactional proxies - are you using Spring transactions, using AspectJ or `@Transactional`?

Spring Autowiring class vs. interface?

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