EntityManager object is not getting injected with

Question

I have been trying to create a job to delete all records from database. This job is deployed with my webservice. In webservice I can easily access my EntityManager and it's having no issues so far. But, whenever I try to access EntityManager in my scheduler then it gives me NullPointerException. Even I have tried to inject a service that I have created and tried to access it's method. The method which have no database related work is working fine and returning me result. But, the method which is using entityManager inside is throwing me the same exception.

While if I directly call the service using URL each and everything works fine in service as well.

@Service
public class DeletionJob {

    @PersistenceContext(unitName = "my_pu")
    private EntityManager em;
    @Autowired
    private REST restClass;

    @Scheduled(fixedDelay=10000)
    public void run() {
        boolean flag = false;
        System.out.println(restClass.executeWithoutDB());
        System.out.println(restClass.executeWithDB());
    }
}

Configuration Class:

@EnableWebMvc
@Configuration
@EnableScheduling
@ComponentScan({ "com.jobs.*" })
@javax.ws.rs.ApplicationPath("webresources")
public class AppConfig extends Application {
     @Bean
     public DeletionJob myDeletionJob() {
         return new DeletionJob();
     } 
    @Bean
    public InternalResourceViewResolver viewResolver() {
        InternalResourceViewResolver viewResolver 
                          = new InternalResourceViewResolver();
        return viewResolver;
    }
        @Bean
        public REST restClass(){
            return new REST(); 
        }
    @Override
    public Set<Class<?>> getClasses() {
        Set<Class<?>> resources = new java.util.HashSet<Class<?>>();
        addRestResourceClasses(resources);
        return resources;
    }


    /**
     * Do not modify addRestResourceClasses() method.
     * It is automatically populated with
     * all resources defined in the project.
     * If required, comment out calling this method in getClasses().
     */
    private void addRestResourceClasses(Set<Class<?>> resources) {
        resources.add(com.service.REST.class);
        // Tried to include deletionjob class here but, no luck still the same.
    // resources.add(com.jobs.DeletionJob.class);
    }
}

persistance.xml file:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="1.0" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
  <persistence-unit name="my_pu" transaction-type="JTA">
    <jta-data-source>ds</jta-data-source>
    <exclude-unlisted-classes>false</exclude-unlisted-classes>
    <properties>
        <property name="eclipselink.logging.level" value="FINE"/>
    </properties>
  </persistence-unit>
</persistence>

I have also tried to use this PersistenceAnnotationBeanPostProcessor component. But after including spring-orm it has even started giving me excpetion of BeanInitializationException. Secondly, I am not fond of using too many libraries. So, would like to do this thing in a simplest possible way. I could do it by looking up JNDI, but, the problem is that I want to use Spring or JAVA EE 6 scheduler API.

Version of GlassFish Server: 4.1

Answer 1

@PersistenceContext is simply getting ignored here.
An entity manager can only be injected in classes running inside a transaction.
Use an EntityManagerFactory to create and destroy an EntityManager.

@PersistenceUnit(unitName = "my_pu")
private EntityManagerFactory entityManagerFactory;

And inside your method use below line to create EntityManager:-

EntityManager entityManager = entityManagerFactory.createEntityManager();

Refer this link:- Injection of Persistence Context in spring

I feel your Persistence Context is not getting initialized properly.