Question

如标题所示 - 如何仅保存从主题到文件的最后一条消息？我尝试过这样做，但是当我打开一个文件时，它包含了我之前发送的最后10条消息。这是我的代码：

public class Consumer {
FileWriter fw;
PrintWriter pw;

public void Consume(String topic){
    Properties props = new Properties();
    props.put("bootstrap.servers", "localhost:9092");
    props.put("group.id", "ranking_consumer");
    props.put("enable.auto.commit", "false");
    props.put("auto.offset.reset", "latest");
    props.put("auto.commit.interval.ms", "1000");
    props.put("session.timeout.ms", "30000");
    props.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
    props.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");

    KafkaConsumer<String, String> consumer = new KafkaConsumer<>(props);
    consumer.subscribe(Arrays.asList(topic));

    File dir = new File("C:/kafka-logs/kafka-logs-0/data");
    if (!dir.exists()) {
        dir.mkdir();
    }

    try{
    while(true){
        ConsumerRecords<String, String> records = consumer.poll(1000);
        int chunkSize = records.count();
        int recordIndex = 0;

        for(ConsumerRecord<String, String> record : records){
            recordIndex++;
            if (recordIndex == chunkSize){
            fw = new FileWriter("C:/kafka-logs/kafka-logs-0/data/msg-"+topic, false);
            pw = new PrintWriter(fw);
            pw.print(record.value());
            pw.close();
            }
        }
    }} catch(IOException e){
        e.printStackTrace();
    }finally{
    consumer.close();
    }
}

}

注意：添加了dbustosp

提出的代码行

注2：更清楚地解释我的问题。我有一个简单的JFrame用于生产者＆＃34;选择文件＆＃34;将.csv文件作为字符串变量发送的按钮。然后我有第二个简单的JFrame用于接收上次发布的消息并将其保存到文件中。也许我对消费者有一个错误的线程声明但是当我从生产者发送一些消息时，我会收到一个带有一些相同消息的文件，而不是只有一个 - 最后一个。下面我发送我的代码给消费者的JFrame和制作人：

public class Producer {

public void Produce(String msg, String topic){

    Properties props = new Properties();
    props.put("bootstrap.servers", "localhost:9092");
    props.put("acks", "all");
    props.put("retries", 0);
    props.put("batch.size", 16384);
    props.put("linger.ms", 1);
    props.put("buffer.memory", 33554432);
    props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
    props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");

    KafkaProducer<String, String> producer = new KafkaProducer<>(props);
    ProducerRecord<String, String> record = new ProducerRecord<>(topic, null, msg);
    producer.send(record);
    producer.close();
}
}

public class Kafka_Consumer extends javax.swing.JFrame {

Thread t;

public Kafka_Consumer() {
    initComponents();
}
private void btn_ReceiveFromKafkaActionPerformed(java.awt.event.ActionEvent evt) {                                                     
    if (textField_topic.getText().equals("")) {
        showMessageDialog(null, "Nie wprowadziłeś/aś tematu!");
    }
    else{
        Consumer consumer = new Consumer();
        t = new Thread(new Runnable(){
        public void run(){
        consumer.Consume(textField_topic.getText());
        }
    });
    t.start();
    }

}

Answer 1

我没有看到任何代码在轮询请求后处理最后一条消息。在您的代码中进行以下修改应该可行。

    libpq-dev python3-dev libxml2-dev libxslt1-dev libldap2-dev libsasl2-dev, build-essential, gcc

如何只保存从主题到文件的最后一条消息？

1 个答案: