如果所有类不在同一个包中，则Spring @autowired不起作用

Question

I have four packages:

1. com.spring.org

   Files: HomeController.java

2. com.spring.org.dao

   Files: SubscriberDao.java , SubscriberDaoImpl.java

3. com.spring.org.model

   Files: Subscriber.java

4. com.spring.org.service

   Files: SubscriberService.java , SubscriberServiceImpl.java

I put all my controller classes in com.spring.org package and others in different packages based on its type. If I run my application I get this error message :

HTTP Status 500 - Servlet.init() for servlet appServlet threw exception No qualifying bean of type [com.spring.org.service.SubscriberService] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency.....

FYI: I am using autowired annoation in my Controller like following:

@Autowired
private SubscriberService subService;

But if I put all my classes and interfaces in com.spring.org package then my application works perfectly.

I have tried using these tags in my servlet-context.xml file to solve the problem, but still it did not work:

<annotation-driven />
<context:annotation-config />
<context:component-scan base-package="com.spring.org.**" />
<context:component-scan base-package="com.spring.org.dao" />
<context:component-scan base-package="com.spring.org.model" />
<context:component-scan base-package="com.spring.org.service" />

I also tried only this:

<context:component-scan base-package="com.spring.org" />

You can see the code of my servlet-context.xml file here http://postimg.org/image/s6bnjccrn/

Could you please tell me how to solve this problem ?

Please let me know if you need to see any other files.

Update

My Code for SubscriberService :

@Service
public interface SubscriberService {

 public void addSubscriber(Subscriber subscriber);
 public void updateSubscriber(Subscriber subscriber);
 public Subscriber getSubscriberById(int subId);
 public List<Subscriber> listSubs();
 public int removeSubscriber(int subId);    

}

Root Cause

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'homeController': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.spring.service.SubscriberService com.spring.org.HomeController.subService; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.spring.service.SubscriberService] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true), @org.springframework.beans.factory.annotation.Qualifier(value=)} org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:292)

Files

It would be very difficult to follow if I paste all my codes here, so I have upload my entire project here https://www.mediafire.com/?crxe7vt7uwyqwtl . I am using Eclipse IDE.

Answer 1

your structure should be like this

SubscriberService Interface

package com.spring.org.service;

public interface SubscriberService {

}

SubscriberServiceImpl.java

package com.spring.org.service;

@Component
@Qualifier("Subscriber")
public class SubscriberServiceImpl implements SubscriberService {

}

'SubscriberServiceImpl1' is a component and it implements 'SubscriberService'.

SubscriberServiceImpl1.java

package com.spring.org.service;

@Component
@Qualifier("Subscriber1")
public class SubscriberServiceImpl1 implements SubscriberService {

}

I setup a Spring context that scans both of these packages for beans marked with '@Component'.

servlet-context.xml

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

HomeController.java

@Controller
public class HomeController {

    @Autowired
    @Qualifier("Subscriber")
    private SubscriberService subService;

}

refer from this link . hope this will help you....

EDIT

as per your package structure your SubscriberServiceImpl class is under package com.spring.org.service just change your base package with com.spring this will work for you

<context:component-scan base-package="com.spring"/>

Answer 2

The problem is you are having multiple implementation of SubscriberService interface.

When you write following code:

@Autowired
private SubscriberService subService;

Spring will look for an implementation of SubscriberService , and since you would be having multiple implementation for it spring will not know which implementation to inject.

Solution to this is using @Qualifier to differentiate between different implementations.

For more and for a demo on @Qualifier visit this link.

Alternatively if you're having a single implementation for SubscriberService make sure both the service and implementation fall under the packages you provide for scan in spring context.

Hope it helps.

Answer 3

You just need to specify the base package:

<context:component-scan base-package="com.spring.org"/>

I believe you should annotate the implementation class instead of the interface.

Answer 4

Try comma-separating the packages, like this:

<context:component-scan 
base-package="com.spring.org,com.spring.org.dao,com.spring.org.model,com.spring.org.service" />

Answer 5

Try to add @Component on SubscriberServiceImpl.

Basically annotations like @Service, @Repository, @Component, etc. they all serve the same purpose:

auto-detection when using annotation-based configuration and classpath scanning.

From my experience I am always using @Service annotation on the interfaces or abstract classes and annotations like @Component and @Repository for their implementation. @Component annotation I am using on those classes which serves basic purposes, simple Spring beans, nothing more. @Repository annotation I am using in the DAO layer, for eg if I have to communicate to the database, have some transactions, etc.

Answer 6

Specify the base scan as follows and remove the annotation from interface and keep only in the implementation class eg @Service, @Repository, @Component, etc.

<context:component-scan base-package="com.spring.org"/> 

EDIT:

I looked into your code.You have given your component scan as

But your SubscriberService.java is in the package com.spring.service. Kindly change the package to com.spring.org.service.

Answer 7

First you have to put this tag in your XML (application context file):

<context:component-scan base-package="com.spring.org"/>

To fix the expection you got you have to change this :

@Autowired
@Qualifier("Subscriber")
private SubscriberService subService

because Spring searches for a bean of type SubscriberService (in your case), and if it finds such bean, it injects it to this method. If it finds two such beans you will get an Exception ( it is the same one in your stack trace).

f you don't want to use two annotations (the @Autowired and @Qualifier ) you can use @Resource to combine these two:

@Resource(name="redBean")
private SubscriberService subService