How does Spring autowire by name when more than one matching bean is found

Question

Suppose I have interfaces such as these   interface Country    class USA implements Country    class UK implements Country      And this snippet of configuration xml    lt bean class  USA   gt   lt bean id  country  class  UK   gt   lt bean id  main  class  Main   gt    How can I control which dependency is autowired below   I d like the UK one   class Main       private Country country       Autowired     public void setCountry Country country            this country   country            I am using Spring 3 0 3 RELEASE

User · Answer

Another way of achieving the same result is to use the @Value annotation:

public class Main {
     private Country country;

     @Autowired
     public void setCountry(@Value("#{country}") Country country) {
          this.country = country;
     }
}

In this case, the "#{country} string is an Spring Expression Language (SpEL) expression which evaluates to a bean named country.

User · Answer

in some case you can use annotation  Primary    Primary class USA implements Country      This way it will be selected as the default autowire candididate  with no need to autowire-candidate on the other bean   for mo deatils look at Autowiring two beans implementing same interface - how to set default bean to autowire

User · Answer

One more solution with resolving by name    Resource name  country     It uses javax annotation package  so it s not Spring specific  but Spring supports it

User · Answer

You can use the  Qualifier annotation  From here  Fine-tuning annotation-based autowiring with qualifiers  Since autowiring by type may lead to multiple candidates  it is often necessary to have more control over the selection process  One way to accomplish this is with Spring s  Qualifier annotation  This allows for associating qualifier values with specific arguments  narrowing the set of type matches so that a specific bean is chosen for each argument  In the simplest case  this can be a plain descriptive value   class Main       private Country country       Autowired      Qualifier  country       public void setCountry Country country            this country   country            This will use the UK add an id to USA bean and use that if you want the USA

User · Answer

This is documented in section 3 9 3 of the Spring 3 0 manual      For a fallback match  the bean name is considered a default qualifier value     In other words  the default behaviour is as though you d added  Qualifier  country   to the setter method

[spring] How does Spring autowire by name when more than one matching bean is found?

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