Apache Kafka
Apache Kafka是一个开源项目,用于基于容错消息传递系统发布和订阅消息。 它设计快速,可扩展和分布。 如果您是Kafka的初学者,或想要更好地了解它,请参阅此链接 - https://www.xnip.cn/docs/apache-kafka
在本章中,我们将了解如何在Spring Boot应用程序中实现Apache Kafka。
首先,我们需要在构建配置文件中添加Spring Kafka依赖项。
Maven用户可以在pom.xml文件中添加以下依赖项。
<dependency>
<groupId>org.springframework.kafka</groupId>
<artifactId>spring-kafka</artifactId>
<version>2.1.0.RELEASE</version>
</dependency>
Gradle用户可以在build.gradle文件中添加以下依赖项。
compile group: 'org.springframework.kafka', name: 'spring-kafka', version: '2.1.0.RELEASE'
制作消息
要向Apache Kafka生成消息,我们需要为Producer配置定义Configuration类,如下所示 -
package cn.xnip.kafkademo;
import java.util.HashMap;
import java.util.Map;
import org.apache.kafka.clients.producer.ProducerConfig;
import org.apache.kafka.common.serialization.StringSerializer;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.kafka.core.DefaultKafkaProducerFactory;
import org.springframework.kafka.core.KafkaTemplate;
import org.springframework.kafka.core.ProducerFactory;
@Configuration
public class KafkaProducerConfig {
@Bean
public ProducerFactory<String, String> producerFactory() {
Map<String, Object> configProps = new HashMap<>();
configProps.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
configProps.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
configProps.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
return new DefaultKafkaProducerFactory<>(configProps);
}
@Bean
public KafkaTemplate<String, String> kafkaTemplate() {
return new KafkaTemplate<>(producerFactory());
}
}
要发布消息,请自动连接Kafka Template对象并生成消息,如图所示。
@Autowired
private KafkaTemplate<String, String> kafkaTemplate;
public void sendMessage(String msg) {
kafkaTemplate.send(topicName, msg);
}
消费消息
要使用消息,我们需要编写一个Consumer配置类文件,如下所示。
package cn.xnip.kafkademo;
import java.util.HashMap;
import java.util.Map;
import org.apache.kafka.clients.consumer.ConsumerConfig;
import org.apache.kafka.common.serialization.StringDeserializer;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.kafka.annotation.EnableKafka;
import org.springframework.kafka.config.ConcurrentKafkaListenerContainerFactory;
import org.springframework.kafka.core.ConsumerFactory;
import org.springframework.kafka.core.DefaultKafkaConsumerFactory;
@EnableKafka
@Configuration
public class KafkaConsumerConfig {
@Bean
public ConsumerFactory<String, String> consumerFactory() {
Map<String, Object> props = new HashMap<>();
props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:2181");
props.put(ConsumerConfig.GROUP_ID_CONFIG, "group-id");
props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class);
props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class);
return new DefaultKafkaConsumerFactory<>(props);
}
@Bean
public ConcurrentKafkaListenerContainerFactory<String, String> kafkaListenerContainerFactory() {
ConcurrentKafkaListenerContainerFactory<String, String>
factory = new ConcurrentKafkaListenerContainerFactory<>();
factory.setConsumerFactory(consumerFactory());
return factory;
}
}
接下来,编写一个监听器来收听消息。
@KafkaListener(topics = "xnip", groupId = "group-id")
public void listen(String message) {
System.out.println("Received Messasge in group - group-id: " + message);
}
让我们从主Spring Boot应用程序类文件中调用ApplicationRunner类run方法中的sendMessage()方法,并使用来自同一类文件的消息。
您的主要Spring Boot应用程序类文件代码如下 -
package cn.xnip.kafkademo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.kafka.annotation.KafkaListener;
import org.springframework.kafka.core.KafkaTemplate;
@SpringBootApplication
public class KafkaDemoApplication implements ApplicationRunner {
@Autowired
private KafkaTemplate<String, String> kafkaTemplate;
public void sendMessage(String msg) {
kafkaTemplate.send("xnip", msg);
}
public static void main(String[] args) {
SpringApplication.run(KafkaDemoApplication.class, args);
}
@KafkaListener(topics = "xnip", groupId = "group-id")
public void listen(String message) {
System.out.println("Received Messasge in group - group-id: " + message);
}
@Override
public void run(ApplicationArguments args) throws Exception {
sendMessage("Hi Welcome to Spring For Apache Kafka");
}
}
完整构建配置文件的代码如下所示。
Maven – pom.xml
<?xml version = "1.0" encoding = "UTF-8"?>
<project xmlns = "http://maven.apache.org/POM/4.0.0"
xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation = "http://maven.apache.org/POM/4.0.0
http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>cn.xnip</groupId>
<artifactId>kafka-demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>kafka-demo</name>
<description>Demo project for Spring Boot</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.9.RELEASE</version>
<relativePath /> <!-- lookup parent from repository -->
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.kafka</groupId>
<artifactId>spring-kafka</artifactId>
<version>2.1.0.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
Gradle – build.gradle
buildscript {
ext {
springBootVersion = '1.5.9.RELEASE'
}
repositories {
mavenCentral()
}
dependencies {
classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
}
}
apply plugin: 'java'
apply plugin: 'eclipse'
apply plugin: 'org.springframework.boot'
group = 'cn.xnip'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = 1.8
repositories {
mavenCentral()
}
dependencies {
compile('org.springframework.boot:spring-boot-starter')
compile group: 'org.springframework.kafka', name: 'spring-kafka', version: '2.1.0.RELEASE'
testCompile('org.springframework.boot:spring-boot-starter-test')
}
现在,创建一个可执行的JAR文件,并使用如下所示的Maven或Gradle命令运行Spring Boot应用程序 -
对于Maven,使用如下所示的命令 -
mvn clean install
在“BUILD SUCCESS”之后,您可以在目标目录下找到JAR文件。
对于Gradle,使用如下所示的命令 -
gradle clean build
在“BUILD SUCCESSFUL”之后,您可以在build/libs目录下找到JAR文件。
使用此处给出的命令运行JAR文件 -
java –jar <JARFILE>
您可以在控制台窗口中看到输出。