Dynamically defining which bean to autowire in Spring (using qualifiers)

Question

I have a Java EE + Spring app that favors annotations over XML configuration. The beans always have prototype scope.

I now have in my app business rules that depend

Answer 1

You could provide a Configuration class that will return the correct bean based on the ThreadLocal value. This assumes you are using Spring 3. I did a little test to make sure that the provider method was called on each request. Here's what I did.

@Configuration
public class ApplicationConfiguration
{
    private static int counter = 0;

    @Bean( name="joel" )
    @Scope( value="request", proxyMode=ScopedProxyMode.TARGET_CLASS)
    List getJoel()
    {
        return Arrays.asList( new String[] { "Joel " + counter++ } );
    }
}

And referenced the value in my Controller as follows.

@Resource( name="joel" )
private List joel;

in your implementation of the provider you could check the ThreadLocal for the locale and return the correct TransactionRules object or something like that. The ScopedProxy stuff is because I was injecting into a Controller, which is Singleton scoped whereas the value is request scoped.