spring autowiring with unique beans: Spring expected single matching bean but found 2

Question

I am trying to autowire some beans (for dependency injection) using Spring for a webapp. One controller bean contains another bean which in turn holds a hashmap of another

Answer 1

If I'm not mistaken, the default bean name of a bean declared with @Component is the name of its class its first letter in lower-case. This means that

@Component
public class SuggestionService {

declares a bean of type SuggestionService, and of name suggestionService. It's equivalent to

@Component("suggestionService")
public class SuggestionService {

or to

<bean id="suggestionService" .../>

You're redefining another bean of the same type, but with a different name, in the XML:

<bean id="SuggestionService" class="com.hp.it.km.search.web.suggestion.SuggestionService">
    ...
</bean>

So, either specify the name of the bean in the annotation to be SuggestionService, or use the ID suggestionService in the XML (don't forget to also modify the <ref> element, or to remove it, since it isn't needed). In this case, the XML definition will override the annotation definition.

Answer 2

The issue is because you have a bean of type SuggestionService created through @Component annotation and also through the XML config . As explained by JB Nizet, this will lead to the creation of a bean with name 'suggestionService' created via @Component and another with name 'SuggestionService' created through XML .

When you refer SuggestionService by @Autowired, in your controller, Spring autowires "by type" by default and find two beans of type 'SuggestionService'

You could do the following

1. Remove @Component from your Service and depend on mapping via XML - Easiest

2. Remove SuggestionService from XML and autowire the dependencies - use util:map to inject the indexSearchers map.

3. Use @Resource instead of @Autowired to pick the bean by its name .

    @Resource(name="suggestionService")
    private SuggestionService service;
   

or

    @Resource(name="SuggestionService")
    private SuggestionService service;

both should work.The third is a dirty fix and it's best to resolve the bean conflict through other ways.

Answer 3

For me it was case of having two beans implementing the same interface. One was a fake ban for the sake of unit test which was conflicting with original bean. If we use

@component("suggestionServicefake")

, it still references with suggestionService. So I removed @component and only used

@Qualifier("suggestionServicefake")

which solved the problem

Answer 4

If you have 2 beans of the same class autowired to one class you shoud use @Qualifier (Spring Autowiring @Qualifier example).

But it seems like your problem comes from incorrect Java Syntax.

Your object should start with lower case letter

SuggestionService suggestion;

Your setter should start with lower case as well and object name should be with Upper case

public void setSuggestion(final Suggestion suggestion) {
    this.suggestion = suggestion;
}