Detecting the insertion of data into the table and calling the method - spring

Question

I have an issue with detecting adding a new row to the table. I want to trigger a method from some service (Spring boot) when somebody executes an insert query on the database (Postgres)
Somebody told me I can use #Scheduled annotation and check if something was added using a repository. I have to make some changes instantly (by using another method). The scheduled method should run every 5 seconds to do this instantly. Of course, this is a really bad idea because it will kill the database someday and it's not efficient.
How can I do this better?

Answer 1

You can write concrete implementer of org.hibernate.integrator.spi.Integrator. and give it to hibernate.integrator_provider
From ServiceRegistry we can get EventListenerRegistry and then append listener of type EventType.POST_INSERT. More events here.
Main Reference Hibernate Integrator Ref
As per the query, I have also added how to call the service method from the listener class.
Here is how I have done it:
package com.example.samplejdbctemplatecall;
import lombok.AllArgsConstructor;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;
import lombok.extern.slf4j.Slf4j;
import org.hibernate.boot.Metadata;
import org.hibernate.engine.spi.SessionFactoryImplementor;
import org.hibernate.event.service.spi.EventListenerGroup;
import org.hibernate.event.service.spi.EventListenerRegistry;
import org.hibernate.event.spi.EventType;
import org.hibernate.event.spi.PostInsertEvent;
import org.hibernate.event.spi.PostInsertEventListener;
import org.hibernate.integrator.spi.Integrator;
import org.hibernate.jpa.boot.spi.IntegratorProvider;
import org.hibernate.persister.entity.EntityPersister;
import org.hibernate.service.spi.SessionFactoryServiceRegistry;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.orm.jpa.HibernatePropertiesCustomizer;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Repository;
import org.springframework.stereotype.Service;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import java.util.Collections;
import java.util.Map;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
#RequestMapping(path = "/entity-listener")
#RestController
public class SampleLogController {
private final SampleLogRepository sampleLogRepository;
private final SampleLogEntries sampleLogEntiries;
#Autowired
public SampleLogController(SampleLogRepository sampleLogRepository, SampleLogEntries sampleLogEntiries) {
this.sampleLogRepository = sampleLogRepository;
this.sampleLogEntiries = sampleLogEntiries;
}
// This is usually post method but for test purpose creating new log with uuid random and inserting
#GetMapping(path = "insert")
public SampleLog insertNewEntry() {
final String uuid = UUID.randomUUID().toString();
final SampleLog sampleLog = new SampleLog();
sampleLog.setMessage(uuid);
return sampleLogRepository.save(sampleLog);
}
#GetMapping(path = "list-recent-inserts")
public Map<Long, String> entries() {
return sampleLogEntiries.data();
}
}
#Slf4j
#Component
class HibernateConfig implements HibernatePropertiesCustomizer {
private final JpaEventListenerIntegrator jpaEventListenerIntegrator;
#Autowired
HibernateConfig(JpaEventListenerIntegrator jpaEventListenerIntegrator) {
this.jpaEventListenerIntegrator = jpaEventListenerIntegrator;
}
#Override
public void customize(Map<String, Object> hibernateProperties) {
log.warn("Called hibernate configuration");
hibernateProperties.put("hibernate.integrator_provider",
(IntegratorProvider) () -> Collections.singletonList(jpaEventListenerIntegrator));
}
}
#Configuration
class SampleConfiguration {
#Bean
SampleLogEntries sampleEntries() {
return new SampleLogEntries();
}
}
class SampleLogEntries {
private final ConcurrentMap<Long, String> map = new ConcurrentHashMap<>();
public void add(SampleLog sampleLog) {
this.map.put(sampleLog.getId(), sampleLog.getMessage());
}
public Map<Long, String> data() {
return Collections.unmodifiableMap(this.map);
}
}
#Repository
interface SampleLogRepository extends CrudRepository<SampleLog, Long> {
}
#Getter
#Setter
#NoArgsConstructor
#AllArgsConstructor
#Entity
class SampleLog {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String message;
}
#Service
#Slf4j
class JpaEventListenerIntegrator implements Integrator, PostInsertEventListener {
private final SampleLogEntries sampleLogEntiries;
#Autowired
JpaEventListenerIntegrator(SampleLogEntries sampleLogEntiries) {
this.sampleLogEntiries = sampleLogEntiries;
}
#Override
public void integrate(Metadata metadata, SessionFactoryImplementor sessionFactory, SessionFactoryServiceRegistry serviceRegistry) {
final EventListenerRegistry eventListenerRegistry = serviceRegistry.getService(EventListenerRegistry.class);
eventListenerRegistry
.appendListeners(EventType.POST_INSERT, this);
}
#Override
public void disintegrate(SessionFactoryImplementor sessionFactory, SessionFactoryServiceRegistry serviceRegistry) {
final EventListenerRegistry eventListenerRegistry = serviceRegistry.getService(EventListenerRegistry.class);
EventListenerGroup<PostInsertEventListener> eventListenerGroup = eventListenerRegistry
.getEventListenerGroup(EventType.POST_INSERT);
log.info("listener attached were: " + eventListenerGroup.getClass().getSimpleName());
log.error("disintegrate : " + getClass().getCanonicalName());
eventListenerGroup.clearListeners();
}
#Override
public void onPostInsert(PostInsertEvent event) {
log.info("Inserted : " + event.getEntity());
final Object entity = event.getEntity();
if (entity instanceof SampleLog) {
sampleLogEntiries.add((SampleLog) entity);
}
}
#Override
public boolean requiresPostCommitHanding(EntityPersister persister) {
return false;
}
}

Answer 2

The answer from #silentsudo is the best one if you only ever use JPA to update the table in question, and if you only have one process updating it.
The issue is that since you are being notified via the JPA interceptor, you won't be notified of any updates that happen outside of your JAP repository.
If you need these other notifications, then you can use Postgres' LISTEN/NOTIFY without polling by using an alternate postgresql JDBC driver, pgjdbc-ng, which implements async notifications.
With this method, you create a trigger in the database to send the notification, so you will be notified of other's updates as well. See https://www.openmakesoftware.com/postgresql-listen-notify-events-example