The previous post introduces way to do Redis CRUD Operations. In this tutorial, we’re gonna look at how to implement Redis Messaging- PubSub with Spring Boot.
Related Post: Spring Data Redis CRUD Operations example with Spring Boot
I. Technology
– Java 1.8
– Maven 3.3.9
– Spring Tool Suite – Version 3.9.0.RELEASE
– Spring Boot: 1.5.9.RELEASE
II. Spring Data Redis Messaging – PubSub
1. Overview
Spring Data provides dedicated messaging integration for Redis that can be roughly divided into two areas of functionality: production (or publication) and consumption (or subscription) of messages.
– Publisher doesn’t know specific subscribers to send messages to. Instead, Publisher specifies channel.
– Subscriber receives messages from one or more topics, without knowledge of Publisher.
2. Maven Dependency
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-redis</artifactId> </dependency> |
3. Redis Configuration
We need:
– connection factory -> JedisConnectionFactory
– a channel -> ChannelTopic
– a template for publisher to publish messages -> RedisTemplate
– a message listener for consumer to consume messages -> RedisMessageListenerContainer
@Bean JedisConnectionFactory jedisConnectionFactory() { return new JedisConnectionFactory(); } @Bean public RedisTemplate<String, Object> redisTemplate() { final RedisTemplate<String, Object> template = new RedisTemplate<String, Object>(); template.setConnectionFactory(jedisConnectionFactory()); template.setValueSerializer(new GenericToStringSerializer<Object>(Object.class)); return template; } @Bean MessageListenerAdapter messageListener() { return new MessageListenerAdapter(new CustomerInfoSubscriber()); } @Bean RedisMessageListenerContainer redisContainer() { final RedisMessageListenerContainer container = new RedisMessageListenerContainer(); container.setConnectionFactory(jedisConnectionFactory()); container.addMessageListener(messageListener(), topic()); container.setTaskExecutor(Executors.newFixedThreadPool(4)); return container; } @Bean CustomerInfoPublisher redisPublisher() { return new RedisCustomerInfoPublisher(redisTemplate(), topic()); } @Bean ChannelTopic topic() { return new ChannelTopic("pubsub:jsa-channel"); } |
We can also supply an executor within RedisMessageListenerContainer for asynch manner of messages.
4. Publish Message
We use convertAndSend() method of the redisTemplate to format and publish message to topic.
RedisTemplate<String, Object> redisTemplate; ChannelTopic topic; public void publish() { redisTemplate.convertAndSend(topic.getTopic(), message); } |
When a message is published, it goes to all the subscribers.
5. Subscribe to Message
We implement the Spring Data Redis-provided MessageListener interface and handle received Message in onMessage() method:
class CustomerInfoSubscriber implements MessageListener { @Override public void onMessage(Message message, byte[] pattern) { // handle message... } } |
III. Practice
1. Project Structure
2. Step by Step
1. Create Spring Boot project & add Dependencies
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-redis</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> |
2. Create DataModel Class
Under package model, create Customer class:
package com.javasampleapproach.redis.pubsub.model; import java.io.Serializable; public class Customer implements Serializable { private static final long serialVersionUID = 1L; private long id; private String firstName; private String lastName; public Customer() { } public long getId() { return id; } public void setId(long id) { this.id = id; } public String getFirstName() { return firstName; } public void setFirstName(String firstName) { this.firstName = firstName; } public String getLastName() { return lastName; } public void setLastName(String lastName) { this.lastName = lastName; } public Customer(long id, String firstName, String lastName) { this.id = id; this.firstName = firstName; this.lastName = lastName; } @Override public String toString() { return String.format("Customer[id=%d, firstName='%s', lastName='%s']", id, firstName, lastName); } } |
3. Create Publisher
Under package producer:
– CustomerInfoPublisher interface:
package com.javasampleapproach.redis.pubsub.producer; public interface CustomerInfoPublisher { void publish(); } |
– And its implementation:
package com.javasampleapproach.redis.pubsub.producer; import java.util.ArrayList; import java.util.Arrays; import java.util.List; import java.util.concurrent.atomic.AtomicInteger; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.data.redis.core.RedisTemplate; import org.springframework.data.redis.listener.ChannelTopic; import com.javasampleapproach.redis.pubsub.model.Customer; public class RedisCustomerInfoPublisher implements CustomerInfoPublisher { List<Customer> customers = new ArrayList<>(Arrays.asList(new Customer(1, "Jack", "Smith"), new Customer(2, "Adam", "Johnson"), new Customer(3, "Kim", "Smith"), new Customer(4, "David", "Williams"), new Customer(5, "Peter", "Davis"))); private final AtomicInteger counter = new AtomicInteger(0); @Autowired private RedisTemplate<String, Object> redisTemplate; @Autowired private ChannelTopic topic; public RedisCustomerInfoPublisher() { } public RedisCustomerInfoPublisher(RedisTemplate<String, Object> redisTemplate, ChannelTopic topic) { this.redisTemplate = redisTemplate; this.topic = topic; } @Override public void publish() { Customer customer = customers.get(counter.getAndIncrement()); System.out.println( "Publishing... customer with id=" + customer.getId() + ", " + Thread.currentThread().getName()); redisTemplate.convertAndSend(topic.getTopic(), customer.toString()); } } |
4. Create Subscriber
Under package consumer:
package com.javasampleapproach.redis.pubsub.consumer; import org.springframework.data.redis.connection.Message; import org.springframework.data.redis.connection.MessageListener; public class CustomerInfoSubscriber implements MessageListener { @Override public void onMessage(Message message, byte[] pattern) { System.out.println("Received >> " + message + ", " + Thread.currentThread().getName() ); } } |
5. Configure Spring Data Redis
Under package config, create RedisConfig class:
package com.javasampleapproach.redis.pubsub.config; import java.util.concurrent.Executors; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.ComponentScan; import org.springframework.context.annotation.Configuration; import org.springframework.data.redis.connection.jedis.JedisConnectionFactory; import org.springframework.data.redis.core.RedisTemplate; import org.springframework.data.redis.listener.ChannelTopic; import org.springframework.data.redis.listener.RedisMessageListenerContainer; import org.springframework.data.redis.listener.adapter.MessageListenerAdapter; import org.springframework.data.redis.serializer.GenericToStringSerializer; import com.javasampleapproach.redis.pubsub.consumer.CustomerInfoSubscriber; import com.javasampleapproach.redis.pubsub.producer.CustomerInfoPublisher; import com.javasampleapproach.redis.pubsub.producer.RedisCustomerInfoPublisher; @Configuration @ComponentScan("com.javasampleapproach.redis.pubsub") public class RedisConfig { @Bean JedisConnectionFactory jedisConnectionFactory() { return new JedisConnectionFactory(); } @Bean public RedisTemplate<String, Object> redisTemplate() { final RedisTemplate<String, Object> template = new RedisTemplate<String, Object>(); template.setConnectionFactory(jedisConnectionFactory()); template.setValueSerializer(new GenericToStringSerializer<Object>(Object.class)); return template; } @Bean MessageListenerAdapter messageListener() { return new MessageListenerAdapter(new CustomerInfoSubscriber()); } @Bean RedisMessageListenerContainer redisContainer() { final RedisMessageListenerContainer container = new RedisMessageListenerContainer(); container.setConnectionFactory(jedisConnectionFactory()); container.addMessageListener(messageListener(), topic()); container.setTaskExecutor(Executors.newFixedThreadPool(4)); return container; } @Bean CustomerInfoPublisher redisPublisher() { return new RedisCustomerInfoPublisher(redisTemplate(), topic()); } @Bean ChannelTopic topic() { return new ChannelTopic("pubsub:jsa-channel"); } } |
6. Application Class
package com.javasampleapproach.redis.pubsub; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.CommandLineRunner; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import com.javasampleapproach.redis.pubsub.producer.CustomerInfoPublisher; @SpringBootApplication public class SpringDataRedisPubSubApplication implements CommandLineRunner { @Autowired private CustomerInfoPublisher redisPublisher; public static void main(String[] args) { SpringApplication.run(SpringDataRedisPubSubApplication.class, args); } @Override public void run(String... arg0) throws Exception { redisPublisher.publish(); redisPublisher.publish(); redisPublisher.publish(); Thread.sleep(50); redisPublisher.publish(); redisPublisher.publish(); } } |
7. Run Spring Boot Application & Check Result
– Config maven build:
clean install
– Run project with mode Spring Boot App
– Check results:
Publishing... customer with id=1, main Publishing... customer with id=2, main Publishing... customer with id=3, main Received >> Customer[id=1, firstName='Jack', lastName='Smith'], pool-1-thread-2 Received >> Customer[id=2, firstName='Adam', lastName='Johnson'], pool-1-thread-3 Received >> Customer[id=3, firstName='Kim', lastName='Smith'], pool-1-thread-4 Publishing... customer with id=4, main Publishing... customer with id=5, main Received >> Customer[id=4, firstName='David', lastName='Williams'], pool-1-thread-2 Received >> Customer[id=5, firstName='Peter', lastName='Davis'], pool-1-thread-2 |
IV. Source Code
Last updated on September 4, 2018.
Hi Team,
Need help asap.
Caused by: org.springframework.data.redis.RedisConnectionFailureException: Cannot get Jedis connection; nested exception is redis.clients.jedis.exceptions.JedisConnectionException: Could not get a resource from the pool
Many Thanks
Sushil
写的不错