Spring – How to add a param to a factory-method of a factory-bean in Spring

factoryspring

let's say I have a factory bean:

<bean id="myFactory" class="com.company.MyFactory" lazy-init="true">
  <property name="myProperty" ref="propA">
</bean>

Let's say propA is a bean injected by IOC used in the factory method. And I have 2 beans generated from this factory:

<bean id="bean1" factory-bean="myFactory" factory-method="instance"/>
<bean id="bean2" factory-bean="myFactory" factory-method="instance"/>

How can I make bean2 to use a different myProperty than bean1 without using a different factory method? Or, how can I pass propA as a parameter to the factory-method from the bean1 or bean2 configuration?

Best Answer

This can be achieved in a slightly different way:

class MyFactory {
    public Bean instance(MyProperty myProperty) {
        return //...
    }
}

Now you can use counterintuitive syntax like following:

<bean id="bean1" factory-bean="myFactory" factory-method="instance">
    <constructor-arg ref="propA"/>
</bean>
<bean id="bean2" factory-bean="myFactory" factory-method="instance">
    <constructor-arg ref="propB"/>
</bean>

Believe it or not but propA and propB will be used as instance() method arguments.

Related Solutions

Java – replace a Spring bean definition at runtime

Here is how I have done it in the past: running services which depend on configuration which can be changed on the fly implement a lifecycle interface: IRefreshable:

public interface IRefreshable {
  // Refresh the service having it apply its new values.
  public void refresh(String filter);

  // The service must decide if it wants a cache refresh based on the refresh message filter.
  public boolean requiresRefresh(String filter);
}

Controllers (or services) which can modify a piece of configuration broadcast to a JMS topic that the configuration has changed (supplying the name of the configuration object). A message driven bean then invokes the IRefreshable interface contract on all beans which implement IRefreshable.

The nice thing with spring is that you can automatically detect any service in your application context that needs to be refreshed, removing the need to explicitly configure them:

public class MyCacheSynchService implements InitializingBean, ApplicationContextAware {
 public void afterPropertiesSet() throws Exception {
  Map<String, ?> refreshableServices = m_appCtx.getBeansOfType(IRefreshable.class);
  for (Map.Entry<String, ?> entry : refreshableServices.entrySet() ) {
   Object beanRef = entry.getValue();
   if (beanRef instanceof IRefreshable) {
    m_refreshableServices.add((IRefreshable)beanRef);
   }
  }
 }
}

This approach works particularly well in a clustered application where one of many app servers might change the configuration, which all then need to be aware of. If you want to use JMX as the mechanism for triggering the changes, your JMX bean can then broadcast to the JMS topic when any of its attributes are changed.

Java – Initializing Spring bean from static method from another Class

The factory-method should only contain the method name, not including the class name.

If you want to use a static factory, give the class of the factory(!) to the bean declaration, if you want to use an instance factory, give the factory-bean to the bean declaration, but don't give both: The class of the created bean is not given in the bean declaration.

So a full example should look like this, using a static factory for validatorFactory and an instance factory for validator:

<bean id="validatorFactory" 
    class="javax.validation.Validation" 
    factory-method="buildDefaultValidatorFactory" />

<bean id="validator" 
    factory-bean="validatorFactory"
    factory-method="getValidator" />

See details on the documentation:

http://static.springsource.org/spring/docs/2.0.x/reference/beans.html#beans-factory-class-static-factory-method

To answer you question - How would you create bean in this kind of a situation in Spring? - Do it exactly as shown here, or if you can, use a utility class like the LocalValidatorFactoryBean, which simplifies the Spring configuration.

Best Answer

Related Solutions

Java – replace a Spring bean definition at runtime

Java – Initializing Spring bean from static method from another Class

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