Java – Spring autowire by name constructor arguments

autowiredconstructorjavaspring

We have a big java applications with thousands of beans, profiling the slow spring context initialization we found that the auto-wiring by type is what's taking most of the context loading time.
Autowiring the bean by name seems to improve the context initialization by an order of magnitude.
However I couldn't find a way to auto-wire beans by name as constructor arguments.

The following is a member autowire that works fine, spring does the lookup by name:

class MyClass {
   @Resource
   private MyBean mybean;
}

But since @Resource only applies to members and methods it doesn't apply to constructor.
We tried both the @Inject with @Named and @Autowired with @Qualifier but Spring does the slow by type lookup for these approaches:

class MyClass {
   @Inject
   public MyClass(@Named("myBean") MyBean myBean) {
   }
}

class MyClass {

   @Autowired
   public MyClass(@Qualifer("myBean") MyBean myBean) {
   }
}

How to tell spring not to lookup by type when using constructor injection?

We understand the advantaged of wire by type (decouple from bean names) yet at this point context loading performance is our biggest concern.

Best Answer

I know it is now a bit old fashioned, but wiring by name is really easy in xml, and Spring supports mixing of xml and java configuration.

Provided bean myBean is defined in xml of java configuration, you can write

<bean id="myClass" class="...MyClass">
    <constructor-arg ref = "myBean"/>
</bean>

or in case of multiple arguments :

<bean id="myClass" class="...MyClass">
    <constructor-arg index="0" ref = "myBean"/>
    <constructor-arg index="1" ref = "myOtherBean"/>
</bean>

EDIT

Alternatively in a java config way you can have :

@Configuration
public class MyClassConfig() {

@Autowire
@Qualifier("myBean")
MyBean myBean;

@Bean
MyClass myclass = new MyClass(myBean);
}

Thanks to jny for suggesting it.

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