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简介：

        kafkaStream：提供了对存储在kafka中的数据进行流式处理和分析的功能

特点：

        KafkasSream提供了一个非常简单轻量的Library，它可以非常方便的嵌入到java程序中，也可以任何方式打包部署

入门案例：

  1、新建工程kafka-demo

           引入kafkaStream依赖

    <dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><!-- kafkfa --><dependency><groupId>org.springframework.kafka</groupId><artifactId>spring-kafka</artifactId><exclusions><exclusion><groupId>org.apache.kafka</groupId><artifactId>kafka-clients</artifactId></exclusion></exclusions></dependency><dependency><groupId>org.apache.kafka</groupId><artifactId>kafka-clients</artifactId></dependency><dependency><groupId>com.alibaba</groupId><artifactId>fastjson</artifactId></dependency><!--kafkaStream--><dependency><groupId>org.apache.kafka</groupId><artifactId>kafka-streams</artifactId><exclusions><exclusion><artifactId>connect-json</artifactId><groupId>org.apache.kafka</groupId></exclusion><exclusion><groupId>org.apache.kafka</groupId><artifactId>kafka-clients</artifactId></exclusion></exclusions></dependency></dependencies>

   2、新建流式处理类

          代码如下

package com.heima.kafkademo.sample;import org.apache.kafka.common.serialization.Serdes;
import org.apache.kafka.streams.KafkaStreams;
import org.apache.kafka.streams.KeyValue;
import org.apache.kafka.streams.StreamsBuilder;
import org.apache.kafka.streams.StreamsConfig;
import org.apache.kafka.streams.kstream.KStream;
import org.apache.kafka.streams.kstream.TimeWindows;
import org.apache.kafka.streams.kstream.ValueMapper;import java.time.Duration;
import java.util.Arrays;
import java.util.Properties;/*
* 流式处理
* */
public class KafkaStreamQuickStart {public static void main(String[] args) {/*创建kafka配置中心并配置参数*/Properties prop = new Properties();//连接地址prop.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG,"192.168.200.130:9092");//key序列化prop.put(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass());//value序列化prop.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.String().getClass());//创建id名称prop.put(StreamsConfig.APPLICATION_ID_CONFIG,"streams-quickstart");//stream构造器StreamsBuilder streamsBuilder = new StreamsBuilder();//流式计算streamProcessor(streamsBuilder);//创建KafkaStream对象KafkaStreams kafkaStreams = new KafkaStreams(streamsBuilder.build(),prop);//开启流式计算kafkaStreams.start();}//流式计算方法private static void streamProcessor(StreamsBuilder streamsBuilder) {//创建kafka对象，同时指定从哪个topic获取消息KStream<String, String> stream = streamsBuilder.stream("itcast-topic-input");//处理消息的valuestream.flatMapValues(new ValueMapper<String, Iterable<?>>() {@Overridepublic Iterable<String> apply(String value) {return Arrays.asList(value.split(" "));}})      //按照value进行聚合.groupBy((key,value)->value)//时间窗口,每隔10秒更新一次.windowedBy(TimeWindows.of(Duration.ofSeconds(10)))//统计单词个数.count()//转换为kStream.toStream().map((key,value)->{System.out.println("key:"+key+",vlaue:"+value);return new KeyValue<>(key.key().toString(),value.toString());})//发送消息.to("itcast-topic-out");}
}

3、启动消费者类和流式处理类监听消息

        使用生产者类发送消息

       消费者和生产者类代码参考Kafka：安装和配置_Success___的博客-CSDN博客

4、测试

        成功接收到消息