I need to inject EntityManager in EntityListener class so that I can perform CRUD operation on it.
POJO:
@Entity
@EntityListner(AuditLogging.class)
class User
{
//Getter / setter of properties
}
AuditLogging (Listner class)
public class AuditInterceptor
{
@PersistenceContext
EntityManager entityManager;
public void setEntityManager(EntityManager entityManager)
{
this.entityManager = entityManager;
}
@PrePersist
public void prePersist(Object obj)
{
// Here I want to use ENTITY manager object so that I can perform CRUD operation
// with prePersist coming object.
entityManager.unwrap(Session.class).save(obj);
// But I am getting NULL POINTER EXCEPTION for entity manager object
}
}
JDBC-CONFIg.xml
<bean id="entityManagerFactory"
class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="dataSource" ref="dataSource" />
<property name="jpaVendorAdapter" ref="hibernateJpaVendorAdapter" />
<property name="packagesToScan" value="com.XXXXX.entity" />
<property name="jpaProperties">
</bean>
<!-- Datasource -->
<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"
destroy-method="close">
<property name="driverClass" value="${jdbc.driver.classname}" />
<property name="jdbcUrl" value="${jdbc.url}" />
</bean>
<!-- transaction Manager -->
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="entityManagerFactory" />
</bean>
EntityListener is not managed by any of the container.EntityListeners are instanciated by JPA, so Spring does not have an opportunity to inject EntityManager. My question is, how we can inject inject EntityManager in EntityListener class so that I can perform CRUD operation on it???
I have faced a similar problem where I was trying to create history records for an entity using EntityListeners.
In order to resolve this problem, I have created utility class BeanUtil
with a static method to get the bean and used this util class to get bean inside my Entitylistener class
@Service
public class BeanUtil implements ApplicationContextAware {
private static ApplicationContext context;
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
context = applicationContext;
}
public static <T> T getBean(Class<T> beanClass) {
return context.getBean(beanClass);
}
}
Now we can call BeanUtil.getBean() to get the bean of any type
public class FileEntityListener {
@PrePersist
public void prePersist(File target) {
perform(target, INSERTED);
}
@Transactional(MANDATORY)
private void perform(File target, Action action) {
EntityManager entityManager = BeanUtil.getBean(EntityManager.class);
entityManager.persist(new FileHistory(target, action));
}
}
We can use this BeanUtil
class to get any spring managed bean from anywhere, To know more you can read my article JPA Auditing: Persisting Audit Logs Automatically using EntityListeners .
Anyways, I got this done by getting entityManager reference from EntityManagerFactory
bean which is configured in my jdbc-config.xml
. But again this is not what I wanted. I wanted to work around with @PersistenceContext
.
@Autowired
EntityManagerFactory entityManagerFactory;
private static EntityManager entityManager;
public void setEntityManagerFactory(EntityManagerFactory entityManagerFactory) {
entityManager=entityManagerFactory.createEntityManager();
this.entityManagerFactory = entityManagerFactory;
}
Here are few notes that we need to keep in mind:
EntityManager
into an EntityListener
(through @PersistenceContext
). EntityListener
is not managed by any of the containers @PersistenceContext
class cannot be static. So we cant attain the instance while class loading.EntityManager
Well, the first solution which came into my mind is a little "hack", but should work.
public class AuditInterceptor {
static setEntityManager emf;
@Autowired
public void setEntityManagerFactory(EntityManager emf) {
AuditInterceptor.emf = emf;
}
@PrePersist
public void prePersist(Object obj) {
EntityManager entityManager = emf.getEntityManager();
// Here I want to use ENTITY manager object so that I can perform CRUD operation
// with prePersist coming object.
entityManager.unwrap(Session.class).save(obj);
// But I am getting NULL POINTER EXCEPTION for entity manager object
}
}
Inside of your code use EntityManager entityManager = emf.getEntityManager()
Declare your AuditInterceptor
as a spring bean ( @Component
with component-scan or define AuditorInterceptor
as a bean)
I used a ThreadLocal to pass the Spring Application Context which contains EntityManager around. Though I am not sure if it is safe Is it safe to pass in the Spring Application Context into a ThreadLocal associated with a request? but so far it is working for me.
The listener can be modified to have autowiring like this. However this needs to be done on on the handlers and not the constructor (doing it on the constructor seems less predictable). You are also not limited to the EntityManager but you have access to the whole context.
@Autowired
private EntityManager entityManager;
@Autowired
private MyDao myDao;
@PrePersist
public void pre() {
SpringBeanAutowiringSupport.processInjectionBasedOnCurrentContext(this);
Objects.requireNotNull(myDao);
myDao.doSomething();
}
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.