根据属性值自动装配Spring bean

Question

nI am developing a Spring MVC web app using Spring 3.2. We will deploy the web app to different customers. Each customer may use one of several implementations of a service interface.

It's possible that the customer may need to reset these values, so we can't just hard-wire the implementation into the application, it needs to be externally configurable. We are already using customer-specific property files that for setting simple properties such as Strings, numbers etc, but I'm asking how to set a particular implementation of an interface.

Eg,

class MyClass {
 // this is straightforward
 @Value("${customer.propertyInPropertyFile}")
 private String customerSpecificString;

 // how to set the correct implementation for each customer?
 private ISomeService service;

}

If there are 4 implementations of ISomeService, we can't autowire, or explicitly set a bean, as this will then be set in the compiled code - and it needs to be configurable after the application is deployed ( it would be OK to restart the application though if need be)..

Does anyone know how to do this? Would this better be performed using Spring EL, or profiles?

Thanks!

Answer 1

So, as I wanted to used Java configuration, I used the following solution:

@Configuration
@Profile("prod")
@EnableAsync
public class ProductionConfig extends BaseConfig
// inject property value which identifies theimplementation to use
Value("${service.impl}")
private String serviceName;

@Bean()

    public IRepository repository() {
        IRepository rc = null;
        if(StringUtils.isEmpty(serviceName)){
            rc =  new Impl1();
        } else if ("sword-mets".equals(serviceName)){
            rc = new Impl2();
        } else {
            rc = new Impl3();
        }
        log.info("Setting in repository implementation " + rc);
        return rc;

    }

So, this isn't quite as clean as the suggested reply using aliases - the Config class needs to know about all the possible implementation classes - but is simple and avoids having to use the XML config just for this bean.