Meu repositório não pode inicializar automaticamente ao usar o Spring Data JPA

Eu estou tentando adicionar dados da primavera jpa ao meu projeto web spring-mvc depois de explorar um par de tutoriais. Mas eu achei meu repositório não pode inicializar automaticamente, eu tenho NullPointerException na minha classe de serviço. Por favor, veja o seguinte código de exemplo:

Meu repositório:

<code>public interface SubjectRepository extends JpaRepository<PSubject, String>{
public Page<PSubject> findByType(String title, Pageable pageable);
public Page<PSubject> findByType(String title);
public Page<PSubject> findByMacaddress(String macaddress, Pageable pageable);
public Page<PSubject> findByMacaddress(String macaddress);
public Page<PSubject> findByUri(String uri);
</code>

}

Meu controlador:

<pre><code>@Controller @RequestMapping("/subject") public class VPSubjectController { .... @RequestMapping("/{id}.htm") public ModelAndView detail(@PathVariable String id) { ModelAndView mav = new ModelAndView("subject/detail"); PSubject subject = subjectService.get(id); .... } } </code></pre>

Meu serviço:

<code>@Service("subjectService")
public class SubjectServiceImpl extends VPService implements SubjectService
{

    @Autowired
    private SubjectRepository subjectRepository;
......
@Override
    @Transactional(propagation=Propagation.REQUIRED, readOnly=true)
    public PSubject get(String subject) {
        PSubject subObj = subjectRepository.findOne(subject);
        return subObj;
    }
.....
</code>

Minha configuração:

<code><?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xmlns:util="http://www.springframework.org/schema/util"
    xmlns:jpa="http://www.springframework.org/schema/data/jpa"
    xsi:schemaLocation="    
           http://www.springframework.org/schema/beans 
           http://www.springframework.org/schema/beans/spring-beans.xsd 
           http://www.springframework.org/schema/context 
           http://www.springframework.org/schema/context/spring-context.xsd 
           http://www.springframework.org/schema/mvc 
           http://www.springframework.org/schema/mvc/spring-mvc.xsd
           http://www.springframework.org/schema/util 
           http://www.springframework.org/schema/util/spring-util-3.0.xsd
           http://www.springframework.org/schema/data/jpa
           http://www.springframework.org/schema/data/jpa/spring-jpa.xsd">
....
<jpa:repositories base-package="com.mypacke.repository"  repository-impl-postfix="Impl" entity-manager-factory-ref="entityManagerFactory" transaction-manager-ref="transactionManager"/>
</code>

....

Eu encontrei nesta linha subjectRepository.findOne (subject), subjectRepository é null, minha pergunta é semelhante a estapostar

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