I am encountering an issue while attempting to invoke Cannot invoke “jakarta.persistence.EntityManager.createQuery(String, java.lang.Class)” in my java application. The error message indicates that “this.em” is null causing the invocation to fail.

I’d appreciate guidance on resolving this error related to the null EntityManager when invoking createQuery(String, Class).

@Configuration
@EnableJpaRepositories
@EnableTransactionManagement
public class ApplicationConfig {
    
    @PersistenceUnit
    private EntityManagerFactory emf;
    
    @Bean
    public DataSource dataSource() {
        EmbeddedDatabaseBuilder builder = new EmbeddedDatabaseBuilder();
        return builder.setType(EmbeddedDatabaseType.HSQL).build();
    }
    
    @Bean
    public LocalContainerEntityManagerFactoryBean entityManagerFactory() {
    
        HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
        vendorAdapter.setGenerateDdl(true);
    
        LocalContainerEntityManagerFactoryBean factory = new LocalContainerEntityManagerFactoryBean();
        factory.setJpaVendorAdapter(vendorAdapter);
        factory.setPackagesToScan("com.project.repository");
        factory.setDataSource(dataSource());
        return factory;
    }
    
    @Bean
    public PlatformTransactionManager transactionManager(EntityManagerFactory entityManagerFactory) {
    
        JpaTransactionManager txManager = new JpaTransactionManager(entityManagerFactory);
        return txManager;
    }

}

@Repository
public class StudentSystemRepository{
    
     @PersistenceContext
     private EntityManager em;
     
     public List<Student> findAll(){
         String jpql = "SELECT t FROM Student t ";
         
         TypedQuery<Student> query = em.createQuery(jpql, Student.class);

         return query.getResultList();
     }
}