Question

我遇到了Kafka 0.9无法通过Java客户端创建主题的奇怪问题。

给出以下代码 -

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Properties;

import kafka.admin.AdminUtils;
import kafka.utils.ZKStringSerializer$;
import kafka.utils.ZkUtils;

import org.I0Itec.zkclient.ZkClient;
import org.I0Itec.zkclient.ZkConnection;

import scala.collection.JavaConversions;

/**
 * This class contains static methods to operate on queues, allowing queue
 * creation and deletion, checking whether queues exist on the broker, and
 * listing all queues on the broker.
 *
 * A topic represents a queue.
 */
public class Topic
{
private static final int DEFAULT_SESSION_TIMEOUT = 10 * 1000;
private static final int DEFAULT_CONNECTION_TIMEOUT = 8 * 1000;
private static final String ZOOKEEPER_CONNECT = "localhost:2181";

/**
 * Opens a new ZooKeeper client to access the Kafka broker.
 */
private static ZkClient connectToZookeeper ()
{
    return new ZkClient(ZOOKEEPER_CONNECT,
                        DEFAULT_SESSION_TIMEOUT,
                        DEFAULT_CONNECTION_TIMEOUT,
                        ZKStringSerializer$.MODULE$);
}

/**
 * Given a ZooKeeper client instance, accesses the broker and returns
 * information about Kafka's contents.
 *
 * @param zookeeperClient A ZooKeeper client to access broker information
 *                        through.
 */
private static ZkUtils zookeeperUtility (ZkClient zookeeperClient)
{
    boolean isSecureCluster = false;
    return new ZkUtils(zookeeperClient, 
                       new ZkConnection(ZOOKEEPER_CONNECT),
                       isSecureCluster);
}

/**
 * Given its name, checks if a topic exists on the Kafka broker.
 *
 * @param name The name of the topic.
 *
 * @return <code>true</code> if the topic exists on the broker,
 *         <code>false</code> if it doesn't.
 */
public static boolean existsTopic (String name)
{
    ZkClient zkClient = connectToZookeeper();
    ZkUtils zkUtils = zookeeperUtility(zkClient);

    boolean topicExists = AdminUtils.topicExists(zkUtils, name);

    zkClient.close();
    return topicExists;
}

/**
 * Creates new topics, which remain persistent on the Kafka broker.
 *
 * @param names The names of the topic.
 * @param partitions The number of partitions in the topic.
 * @param replication The number of brokers to host the topic.
 */
public static void createTopics (ArrayList<String> names, int partitions, int replication)
{
    ZkClient zkClient = connectToZookeeper();
    ZkUtils zkUtils = zookeeperUtility(zkClient);

    for (String name: names)
    {
        if (existsTopic(name))
            continue;

        AdminUtils.createTopic(zkUtils, name, partitions, replication, new Properties());

    }

    zkClient.close();
}

/**
 * Given its name, deletes a topic on the Kafka broker.
 *
 * @param names The name of the topic.
 */
public static void deleteTopics (ArrayList<String> names)
{
    ZkClient zkClient = connectToZookeeper();
    ZkUtils zkUtils = zookeeperUtility(zkClient);

    for (String name: names)
    {
        if (!existsTopic(name))
            return;

        AdminUtils.deleteTopic(zkUtils, name);
    }

    zkClient.close();
}

/**
 * Lists all topics on the Kafka broker.
 */
public static void listTopics ()
{
    ZkClient zkClient = connectToZookeeper();
    ZkUtils zkUtils = zookeeperUtility(zkClient);

    List<String> brokerTopics = JavaConversions.seqAsJavaList(zkUtils.getAllTopics());

    for (String topic: brokerTopics)
        System.out.println(topic);

    zkClient.close();
}
}

deleteTopics()和existsTopic()工作正常，暗示一切都是最新的，我正确访问AdminUtils方法。但是，createTopics()在运行时崩溃，但出现以下异常 - java.lang.NoClassDefFoundError: scala/Product$class

可能会发生什么？

Answer 1

有two Kafka compiles需要不同的Scala库，Scala 2.10或Scala 2.11。如果您使用下载站点中的两个tgz之一，则会获得正确的scala库作为其中一部分。如果你使用maven，你可能需要单独添加依赖项（我只使用过tgz，所以我不知道maven的依赖。）

Kafka AdminUtils.createTopic引发java.lang.NoClassDefFoundError：scala / Product $ class

1 个答案: