Programmatically set a specific bean object - Spring DI

Question

In my program I need to programmatically configure an ApplicationContext. Specifically, I have a reference to an instance of MyClass and I want to define it as a new bean called "xxyy".

public void f(MyClass mc, ApplicationContext ac) {
  // define mc as the "xxyy" bean on ac ???
  ...
  ...

  // Now retrieve that bean
  MyClass bean = (MyClass) ac.getBean("xxyy");

  // It should be the exact same object as mc
  Assert.assertSame(mc, bean); 
}

The BeanDefinition API let's me specify the class of the new bean, so it does not work for me since I want to specify the instance. I managed to find a solution but it took two additional factory beans which seems like too much code for such an eartly purpose.

Is there a standard API that addresses my needs?

Answer 1

You need to jump through a few hoops to do this. The first step is to obtain a reference to the context's underlying BeanFactory implementation. This is only possible if your context implements ConfigurableApplicationContext, which most of the standard ones do. You can then register your instance as a singleton in that bean factory:

ConfigurableApplicationContext configContext = (ConfigurableApplicationContext)appContext;
SingletonBeanRegistry beanRegistry = configContext.getBeanFactory();
beanRegistry.registerSingleton("xxyy", bean);

You can "insert" any object into the context like this.