How can I inject a bean into an ApplicationContext before it loads from a file?

Question

I have a FileSystemXmlApplicationContext and I would like the beans defined in the XML to take as a constructor argument a bean which is not declared in Spring

Answer 1

If the existing context needs the bean you wish to inject then things need to be done a little differently. The approaches in other answers don't work for the following reasons

• Context cannot be refreshed until the missing bean is registered
• refresh() causes the injected bean to be destroyed.

This can be worked around by using a "bean factory post processor", this allows code to be run after the context is loaded but before it it refreshed.

ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext();
applicationContext.setConfigLocation("/org/example/app-context.xml");
applicationContext.getBeanFactoryPostProcessors().add(new BeanFactoryPostProcessor() {

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
        beanFactory.registerSingleton("customBeanName", customBean);
    }
});
applicationContext.refresh();

Answer 2

As I had trouble solving this with an AnnotationConfigApplicationContext, I found the following alternative:

DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();
beanFactory.registerSingleton("customBean", new CustomBean());
context = new AnnotationConfigApplicationContext(beanFactory);
context.register(ContextConfiguration.class);
context.refresh();

Answer 3

How about programmatically creating an empty parent context first, registering your object as a singleton with that context's BeanFactory using the fact that getBeanFactory returns an implementation of SingletonBeanRegistry.

parentContext = new ClassPathXmlApplicationContext();
parentContext.refresh(); //THIS IS REQUIRED
parentContext.getBeanFactory().registerSingleton("myBean", myBean)

Then specify this context as a parent to your "real" context The beans in the child context will then be able to refer to the bean in the parent.

String[] fs = new String[] { "/path/to/myfile.xml" } 
appContext = new FileSystemXmlApplicationContext(fs, parentContext);