一，新建Spring Boot

最近忙着搞低代码开发，好久没新建spring项目了，结果今天心血来潮准备建个springboot项目

注意Type选Maven，java选8，其他默认

1，Maven配置

点下一步后完成就新建了一个spring boot项目，配置下Maven环境，主要是settings.xml文件，里面要包含阿里云仓库，不然可能依赖下载不下来

2，无法识别为SpringBoot项目

在maven配置没问题的前提下，IDEA无法识别这是一个Spring Boot项目，倒腾半天，终于发现问题原因所在=======>是Maven版本太高的原因

把.mvn/wrapper目录下的maven-wrapper.properties文件第一行的版本号降低，比如说降为3.5.4，然后重新点下Maven的同步按钮

3，无效的源发行版

接下来运行项目报错：java: 无效的源发行版: 14

修改pom.xml中java.version值为8，原来是17

	<properties><java.version>17</java.version></properties>

4，无法访问SpringApplication

继续运行，继续报错
降低spring-boot-starter-parent版本，原来是3.1.3，改为2.7.2

5，运行直接Finish

继续运行，没报错，服务直接Finished

需要添加web依赖

 		<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency>

6，服务运行成功

终于，一个空的spring boot项目成功跑起来了，喜极而泣

二，安装启动Kafka

1，下载

官网=>https://kafka.apache.org/downloads，下载最新版的kafka，目前是3.5.1

2，配置

解压到D盘Config目录下即完成安装，目录为D:\Config\kafka_2.13-3.5.1
修改配置文件
(1) server.properties

broker.id=1
log.dirs=/Config/kafka_2.13-3.5.1/logs-kafka

(2) zookeeper.properties

dataDir=/Config/kafka_2.13-3.5.1/logs-zookeeper

3，启动

先启动zookeeper

bin\windows\zookeeper-server-start.bat config\zookeeper.properties	

再启动kafka

bin\windows\kafka-server-start.bat config\server.properties

停止的时候，先停止kafka，再停止zookeeper，直接ctrl+c停止

4，其他命令

1，查看topic列表

bin\windows\kafka-topics.bat --list --bootstrap-server localhost:9092

2，查看topic具体信息

bin\windows\kafka-topics.bat --describe --bootstrap-server localhost:9092 --topic test

3，创建topic

bin\windows\kafka-topics.bat --create --bootstrap-server localhost:9092 --replication-factor 1 --partitions 1 --topic test

三，生产消费消息

1，加入依赖

 		<dependency><groupId>org.springframework.kafka</groupId><artifactId>spring-kafka</artifactId></dependency>

2，yam配置文件

application.yaml

spring:profiles:active: dev

application-dev.yaml

server:port: 8082servlet:context-path: /test-kafkaspring:cache:type: ehcacheconfig: classpath:ehcache.xmljpa:database-platform: com.enigmabridge.hibernate.dialect.SQLiteDialectkafka:bootstrap-servers: 127.0.0.1:9092consumer:group-id: kafka-demo-kafka-groupkey-deserializer: org.apache.kafka.common.serialization.StringDeserializer value-deserializer: org.apache.kafka.common.serialization.StringDeserializer producer:key-serializer: org.apache.kafka.common.serialization.StringSerializer value-serializer: org.apache.kafka.common.serialization.StringSerializer retries: 10

3，报错enabled mechanisms are []

Connection to node -1 (activate.navicat.com/127.0.0.1:9092) failed authentication due to: Unexpected handshake request with client mechanism PLAIN, enabled mechanisms are []

这个错误我本地测试下来是因为没把账号密码配置这块注释掉

4，生产者生产消息

@Slf4j
@Component
public class KafkaProducer {@Autowiredprivate KafkaTemplate<String, String> kafkaTemplate;public String sendMessage(String content) {String topic = "test_topic";kafkaTemplate.send(topic, content).addCallback(success -> {String topic = success.getRecordMetadata().topic();int partition = success.getRecordMetadata().partition();long offset = success.getRecordMetadata().offset();log.info("发送成功：主题：{}，分区：{}，偏移量：{}",topic,partition,offset);}, failure -> {log.info("发送失败：{}",failure.getMessage());});return "发送成功";}
}

5，订阅和消费消息

一，订阅主题
1，获取消费者

import org.apache.kafka.clients.consumer.ConsumerConfig;
import org.apache.kafka.clients.consumer.KafkaConsumer;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Configuration;
import org.springframework.stereotype.Component;import java.util.Properties;/*** kafka消费者配置* @author liuxunming*/
@Configuration
@Component
public class KafkaConfig {@Value("${spring.kafka.bootstrap-servers}")private String bootstrapServers;@Value("${spring.kafka.consumer.group-id}")private String groupId;@Value("${spring.kafka.consumer.key-deserializer}")private String keyDeserializer;@Value("${spring.kafka.consumer.value-deserializer}")private String valueDeserializer;public KafkaConsumer<String, String> createConsumer() {Properties props = new Properties();props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapServers);props.put(ConsumerConfig.GROUP_ID_CONFIG, groupId);props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, keyDeserializer);props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, valueDeserializer);props.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");KafkaConsumer<String, String> consumer = new KafkaConsumer<>(props);return consumer;}}

2，订阅topic

 		KafkaConsumer<String, String> consumer = kafkaConfig.createConsumer();consumer.subscribe(Collections.singleton("traffic"));

3，拉取消息

 ConsumerRecords<String, String> records = consumer.poll(Duration.ofMillis(100));for (ConsumerRecord<String, String> record : records) {String key = record.key();String value = record.value();log.info("\n收到消息key=>{}\n收到消息value=>{}",key,value);
}

4，消费位移，释放资源

// 提交消费位移
consumer.commitSync();
// 关闭消费者以释放资源
consumer.close();

二，点对点模式

@Slf4j
@Component
public class KafkaConsumer {@KafkaListener(topics = {"test_topic"})public void handlerMsg(String content) {log.info("接收到消息：消息值：{} ",content);}
}

6，接口

@Slf4j
@RestController
public class KafkaController {@Autowiredprivate KafkaProducer kafkaProducer;@PostMapping("/sendMessage")public String sendMessage(@RequestParam String content) {kafkaProducer.sendMessage(content);return "ok";}
}

7，测试结果

接收到消息

四，参考博文

1. 解决IDEA无法识别SpringBoot项目
2. SpringBoot从入门到精通（十二）SpringBoot集成Kafka
3. Kafka的下载安装以及使用
4. Kafka消息消费流程详解
5. Kafka之Consumer使用与基本原理