spring autowiring with unique beans: Spring 期望单个匹配 bean 但找到了 2
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 set of beans. For now the map only has one entry. When i run in tomcat and call the service I get an error saying that the second bean (held in the controller) is not unique
No unique bean of type [com.hp.it.km.search.web.suggestion.SuggestionService] is defined: expected single matching bean but found 2: [suggestionService, SuggestionService]
I cannot see where I am defining the bean twice however am new to Spring and autowiring so I may be missing something fundamental. Source code for xml and 2 class listed below...
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">
<context:component-scan base-package="com.hp.it.km.search.web.suggestion" />
<mvc:annotation-driven />
<context:annotation-config />
<bean id="SuggestionController" class="com.hp.it.km.search.web.suggestion.SuggestionController">
<property name="service">
<ref bean="SuggestionService" />
</property>
</bean>
<bean id="SuggestionService" class="com.hp.it.km.search.web.suggestion.SuggestionService">
<property name="indexSearchers">
<map>
<entry key="KMSearcher"> <ref bean="KMSearcherBean"></ref></entry>
</map>
</property>
</bean>
<bean id="KMSearcherBean" class="com.hp.it.km.search.web.suggestion.SuggestionIndexSearcher">
<constructor-arg index="0" value="KMSearcher" />
<constructor-arg index="1" value="C://dev//workspace//search-restful-webapp//src//main//resources//indexes//keyword" />
</bean>
The class asscoaites with the autowired controller and service bean are here...
@Controller
public class SuggestionController {
private SuggestionService service;
@Autowired
public void setService(SuggestionService service) {
this.service = service;
}
public SuggestionService getService() {
return service;
}
and...
@Component
public class SuggestionService {
private Map<String, IndexSearcher> indexSearchers = new HashMap<String, IndexSearcher>();
@Autowired
public void setIndexSearchers(Map<String, IndexSearcher> indexSearchers) {
this.indexSearchers = indexSearchers;
}
public SuggestionService() {
super(); }
Please Help!
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 one of the following
Remove @Component from your Service and depend on mapping via XML - Easiest Remove SuggestionService from XML and autowire the dependencies - use util:map to inject the indexSearchers map. 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.
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;
}
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
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.
