Java集成pubSub

什么是pubSub

pubSub是“Publish/Subscribe”（发布/订阅）的缩写，是一种消息传递范式。在pubSub模式中，消息的发送者（发布者）和接收者（订阅者）不直接通信，而是通过一个消息代理（broker）来传递消息。发布者将消息发送到代理，订阅者从代理订阅消息，并在消息到达时收到通知。

在Java中集成pubSub

在Java中集成pubSub最常用的库是Apache Kafka。Apache Kafka是一个分布式的流处理平台，支持pubSub模式。

步骤

  1. 首先，引入Apache Kafka的依赖：
dependencies {
    implementation 'org.apache.kafka:kafka-clients:2.8.1'
}
  1. 创建一个生产者（发布者）：
Properties props = new Properties();
props.put("bootstrap.servers", "localhost:9092");
props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");

Producer<String, String> producer = new KafkaProducer<>(props);

ProducerRecord<String, String> record = new ProducerRecord<>("topic", "key", "value");
producer.send(record);
producer.close();
  1. 创建一个消费者（订阅者）：
Properties props = new Properties();
props.put("bootstrap.servers", "localhost:9092");
props.put("group.id", "test-group");
props.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
props.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");

Consumer<String, String> consumer = new KafkaConsumer<>(props);

consumer.subscribe(Collections.singletonList("topic"));

while (true) {
    ConsumerRecords<String, String> records = consumer.poll(Duration.ofMillis(100));
    for (ConsumerRecord<String, String> record : records) {
        System.out.printf("offset = %d, key = %s, value = %s%n", record.offset(), record.key(), record.value());
    }
}

示例

下面是一个使用Apache Kafka实现pubSub的示例代码：

```java
// 生产者
Properties props = new Properties();
props.put("bootstrap.servers", "localhost:9092");
props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");

Producer<String, String> producer = new KafkaProducer<>(props);

ProducerRecord<String, String> record = new ProducerRecord<>("topic", "key", "value");
producer.send(record);
producer.close();

// 消费者
Properties props = new Properties();
props.put("bootstrap.servers", "localhost:9092");
props.put("group.id", "test-group");
props.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
props.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");

Consumer<String, String> consumer = new KafkaConsumer<>(props);

consumer.subscribe(Collections.singletonList("topic"));

while (true) {
    ConsumerRecords<String, String> records = consumer.poll(Duration.ofMillis(100));
    for (ConsumerRecord<String, String> record : records) {
        System.out.printf("offset = %d, key = %s, value = %s%n", record.offset(), record.key(), record.value());
    }
}

总结

通过上述示例，我们可以看到在Java中集成pubSub并不复杂，借助Apache Kafka等库，我们可以轻松实现发布/订阅模式的消息传递。希望以上内容能够帮助您更好地理解和应用pubSub模式。