Spring bean with no id or name

Question

I'm reviewing some Spring code, and I see a few bean defs that do not have an id or a name. The person who did it is not around to ask. The application is working fine. I am not familiar what this necessarily means. Anybody know if this means anything in particular? Thanks

Answer 1

One possibility is that you can define a bean in place, and so you don't need an id since you don't need to refer to it from anywhere else. Say I have a Foo object that takes a Bar property:

<bean id="foo" class="Foo">
     <property name="bar">
         <bean class="Bar">
     </property>
</bean>

The Bar bean doesn't need a name because it's only used to set that one property.

Answer 2

thanks, but that's not what i have here. the bean defn in question is on its own

Answer 3

The id and name attributes are optional and are used to reference the bean definition from other definitions. Look at the official Spring documentation for more detail.

Answer 4

Check the possibility of auto-wiring. An other bean could reference the unnamed bean by having the autowire property set to byType.

This is just a guess. Without a concrete example, I can't say any more.

Answer 5

Some beans are not required to be accessed by other beans in the context file or programmatically. So as mentioned by JacobM, they don't require an id or name as they're not referenced.

Such an example would be a PropertyPlaceholderConfigurer, which reads a property file, then allows for runtime property replacement in the context definition.

The example definition would be

<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
  <property name="location" value="myapp.properties" />
</bean>

The JavaDoc provides further documentation on this object, but further on in the file you can reference properties from your file by just using the standard template replace placeholder ${...}.

Answer 6

Beans without id or name can still be referenced by the class name. Spring names those beans automatically using the class name and if there is more than one bean of the same class it appends a number to them. Anonymous beans are usually defined inside a property tag, but if they're just there maybe there's autowiring configured in some other beans. Anyway, I think adding a name or id to those beans won't break your application.

Answer 7

As a couple of people mentioned above, not all bean-grabbing is based on name/ID; some of it is based on type. For example, there is a method

BeanFactoryUtils.beansOfTypeIncludingAncestors(...)

that grabs all the beans of some given type. This is used for example by the Spring Web MVC DispatcherServlet (among many other places) to discover beans by type, such as HandlerMappings, HandlerAdapters, HandlerExceptionResolvers and so forth. Contrast this with cases where the bean must have a specific well-known name/ID to be found, such as the LocaleResolver (ID must be "localeResolver" or it won't be found) and ThemeResolver (ID must be "themeResolver" or it won't be found).

Answer 8

Thanks for all of the help