Spring 3 Autowired BeanInitializationException

Question

I have a big problem with @Autowired that always return with exception

Initialization of bean failed; nested exception is org.springframework.beans.factory.BeanInitializationException: Property 'serviceFactory' is required for bean 'A'

Here are the brief of everything (I am using Spring 3.2 and I have put all the jar in the right place WEB-INF/lib).

applicationContext.xml

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:p="http://www.springframework.org/schema/p" 
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:context="http://www.springframework.org/schema/context"
        xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-3.2.xsd">

<context:annotation-config />
<context:component-scan base-package="com.sc" />

<!-- Comment out - we are going to use @Component @Autowired - 2014-01-07
<bean id="A" class="com.sc.A">
  <property name="serviceFactory" ref="serviceFactoryBean" />
</bean> 
-->

<bean id="serviceFactoryBean" class="com.sc.ServiceFactory" autowire="byName" />

</beans>

Content of Class com.sc.A

@Component
public class A
{

private Logger logger = Logger.getLogger(A.class);

// @Autowired -- 2014-01-07 comment out as not need it since annotation in setter below
// @Qualifier("serviceFactoryBean")
private ServiceFactory serviceFactory;

public A()
{ }

@Autowired // add 2014-01-07
@Required
public void setServiceFactory(ServiceFactory serviceFactory)
{
  this.serviceFactory = serviceFactory;
}

public boolean checkSomething() 
{
  if(this.serviceFactory == null)
   logger.error("serviceFactory is null. Autowired failed");

 // do something
}


} // end of class A

Content of class com.sc.ServiceFactory

// @Component -- comment out 2014-01-07
public class ServiceFactory
{
  // do whatever
}

then I compiled the classes and ran it in jetty and when jetty went up, It always throw up long exception of

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'A' defined in URL ... Initialization of bean failed; nested exception is org.springframework.beans.factory.BeanInitializationException: Property 'serviceFactory' is required for bean 'A'

I have try many combination with and without annotation to no avail. It is very frustrating to face this error.

Please help

Answer 1

There are a few things wrong (or rather misunderstood) in your question.

With your current context, you are declaring two bean definitions for each of A and ServiceFactory. One implicitly from the @Component annotation and <component-scan> and another from the explicit <bean> declarations. Choose one or the other or you might find yourself in a position where Spring doesn't know which to use.

With the above, what happens is that Spring tries to generate an A bean because of its @Component annotation and sees @Required on the setServiceFactory() method, but doesn't know what to do with it. @Required's javadoc states

Marks a method (typically a JavaBean setter method) as being 'required': that is, the setter method must be configured to be dependency-injected with a value.

But in your case, it isn't. Add @Autowired to it.

@Required
@Autowired
public void setServiceFactory(ServiceFactory serviceFactory) {
    this.serviceFactory = serviceFactory;
}

Now Spring will know what to do with that method, ie. inject a ServiceFactory bean.