Question

我正在尝试创建一个将Avro流式传输到kafka主题的Java生产者。我试图重现Confluent's official documentation

中提供的示例

但是无法找到GenericRecord类 - 如下所示使用。

import org.apache.avro.Schema;
import org.apache.avro.generic.GenericData;
import org.apache.avro.generic.GenericRecord;

Schema.Parser parser = new Schema.Parser();
Schema schema = parser.parse(userSchema);
GenericRecord avroRecord = new GenericData.Record(schema);

以下是报告的错误：

Error: A JNI error has occurred, please check your installation and try again
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/avro/generic/GenericRecord
    at java.lang.Class.getDeclaredMethods0(Native Method)
    at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)
    at java.lang.Class.privateGetMethodRecursive(Class.java:3048)
    at java.lang.Class.getMethod0(Class.java:3018)
    at java.lang.Class.getMethod(Class.java:1784)
    at sun.launcher.LauncherHelper.validateMainClass(LauncherHelper.java:544)
    at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:526)
Caused by: java.lang.ClassNotFoundException: org.apache.avro.generic.GenericRecord
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 7 more

这是我的pom.xml文件

<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/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.giorgos.currencies</groupId>
  <artifactId>giorgos-fx_currencies</artifactId>
  <packaging>jar</packaging>
  <version>1.0-SNAPSHOT</version>
  <name>george-fx_currencies</name>
  <url>http://maven.apache.org</url>

    <repositories>
        <repository>
            <id>apache-repo</id>
            <name>Apache Repository</name>
            <url>https://repository.apache.org/content/repositories/releases</url>
            <releases>
                <enabled>true</enabled>
            </releases>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
        <repository>
            <id>confluent</id>
            <url>http://packages.confluent.io/maven/</url>
        </repository>
    </repositories>


    <properties>
        <kafka.version>0.8.2.1</kafka.version>
        <kafka.scala.version>2.10</kafka.scala.version>
        <confluent.version>4.0.0</confluent.version>
        <avro.version>1.7.6</avro.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

   <dependencies>
        <dependency>
            <groupId>org.apache.avro</groupId>
            <artifactId>avro</artifactId>
            <version>${avro.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.avro</groupId>
            <artifactId>avro-maven-plugin</artifactId>
            <version>${avro.version}</version>
        </dependency>
        <dependency>
            <groupId>io.confluent</groupId>
            <artifactId>kafka-avro-serializer</artifactId>
            <version>${confluent.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.kafka</groupId>
            <artifactId>kafka-clients</artifactId>
            <version>${kafka.version}</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.avro</groupId>
                <artifactId>avro-maven-plugin</artifactId>
                <version>${avro.version}</version>
                <executions>
                    <execution>
                        <phase>generate-sources</phase>
                        <goals>
                            <goal>schema</goal>
                            <goal>protocol</goal>
                            <goal>idl-protocol</goal>
                        </goals>
                        <configuration>
                            <sourceDirectory>${project.basedir}/src/main/resources/avro</sourceDirectory>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <finalName>uber-${project.artifactId}-${project.version}</finalName>
                </configuration>
            </plugin>
        </plugins>
    </build>


</project>

我想知道是否在pom.xml中定义了错误版本的avro / kafka / confluent，但我无法找到错误。另请注意，mvn package会导致成功构建，但不会报告任何错误。

修改我试图对这些行进行注释，但在以下行中观察到类似的行为：

KafkaProducer producer = new KafkaProducer(props);

出现以下错误：

Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/kafka/clients/producer/KafkaProducer
    at com.giorgos.currencies.TestFX.main(TestFX.java:103)
Caused by: java.lang.ClassNotFoundException: org.apache.kafka.clients.producer.KafkaProducer
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 1 more

这就是我运行程序的方式：

java -cp target/giorgos-fx_currencies-1.0-SNAPSHOT.jar com.giorgos.currencies.TestFX command-line-argument

Answer 1

由于您正在使用shade插件，因此这些类是此文件的一部分

target/uber-giorgos-fx_currencies-1.0-SNAPSHOT.jar

用它来运行你的代码。

无法在Kafka Producer中实例化GenericRecord以将avro流式传输到主题

1 个答案: