Maven命令行执行错误ClassNotFoundException答案

【问题标题】：Maven command line execution error ClassNotFoundExceptionMaven命令行执行错误ClassNotFoundException
【发布时间】：2020-02-29 00:10:17
【问题描述】：

我正在使用 Kafka，并且我创建了一个简单的 maven 项目来使用 Kafka Streams API。当我从 IntelliJ 执行项目时，它运行正常。当我尝试从命令行运行项目时，出现以下错误：

Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/kafka/common/serialization/Serdes
at pega.main(pega.java:18)
Caused by: java.lang.ClassNotFoundException: org.apache.kafka.common.serialization.Serdes
at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
at java.lang.ClassLoader.loadClass(ClassLoader.java:419)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:352)
at java.lang.ClassLoader.loadClass(ClassLoader.java:352)
... 1 more

java代码和pom.xml如下：

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>vodafone.vfgr.pega</groupId>
    <artifactId>s_order_project</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.json/json -->
        <dependency>
            <groupId>org.json</groupId>
            <artifactId>json</artifactId>
            <version>20190722</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.apache.kafka/kafka-streams -->
        <dependency>
            <groupId>org.apache.kafka</groupId>
            <artifactId>kafka-streams</artifactId>
            <version>2.3.1</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.6.0</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

Pega.java

public class pega {
    public static void main(String[] args) {
        Properties properties = new Properties();
        properties.put(StreamsConfig.APPLICATION_ID_CONFIG, "pega-app");
        properties.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
        properties.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
        properties.put(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass());
        properties.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.String().getClass());
        properties.put(StreamsConfig.COMMIT_INTERVAL_MS_CONFIG, 1000);

        StreamsBuilder builder = new StreamsBuilder();

        KStream<String, String> s_order = builder.stream("gg-input-topic", Consumed.with(Serdes.String(),Serdes.String()))
                .selectKey((k,v) -> v);
        s_order.to("pega-output-topic", Produced.with(Serdes.String(),Serdes.String()));

        KafkaStreams streams = new KafkaStreams(builder.build(), properties);
        streams.start();

        System.out.println(streams.toString());

        Runtime.getRuntime().addShutdownHook(new Thread(streams::close));
    }
}

我在终端中执行的命令如下：

mvn clean

[INFO] Scanning for projects...
[INFO]
[INFO] -----------------< vodafone.vfgr.pega:s_order_project >-----------------
[INFO] Building s_order_project 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ s_order_project ---
[INFO] Deleting /home/christoforos/IdeaProjects/s_order_project/target
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  0.813 s
[INFO] Finished at: 2020-02-28T17:15:11+02:00
[INFO] ------------------------------------------------------------------------

mvn package

[INFO] Scanning for projects...
[INFO]
[INFO] -----------------< vodafone.vfgr.pega:s_order_project >-----------------
[INFO] Building s_order_project 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ s_order_project ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] Copying 1 resource
[INFO]
[INFO] --- maven-compiler-plugin:3.6.0:compile (default-compile) @ s_order_project ---
[INFO] Changes detected - recompiling the module!
[WARNING] File encoding has not been set, using platform encoding UTF-8, i.e. build is platform dependent!
[INFO] Compiling 1 source file to /home/christoforos/IdeaProjects/s_order_project/target/classes
[INFO]
[INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ s_order_project ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory /home/christoforos/IdeaProjects/s_order_project/src/test/resources
[INFO]
[INFO] --- maven-compiler-plugin:3.6.0:testCompile (default-testCompile) @ s_order_project ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ s_order_project ---
[INFO] No tests to run.
[INFO]
[INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ s_order_project ---
[INFO] Building jar: /home/christoforos/IdeaProjects/s_order_project/target/s_order_project-1.0-SNAPSHOT.jar
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  4.474 s
[INFO] Finished at: 2020-02-28T17:15:23+02:00
[INFO] ------------------------------------------------------------------------

java -cp target/s_order_project-1.0-SNAPSHOT.jar pega

还有我得到错误的地方。你能帮我解决这个问题吗？（我提醒当我从 IntelliJ 执行时它运行正确）

【问题讨论】：

您正在尝试运行不包含所有依赖项的 jar 文件，因此请通过 maven-assembly-plugin 或 maven-shade-plugin 创建可执行的 ueber-jar ...
第二个选项是枚举类路径中所有必需的依赖项，这个插件可以帮助maven.apache.org/plugins/maven-dependency-plugin/…

标签： java maven apache-kafka apache-kafka-streams

【解决方案1】：

它没有在终端上运行，因为所需的依赖项不在类路径中。它在 IntelliJ 中运行，因为 IntelliJ IDEA 的类路径中提供了依赖项。

您有两种选择：

为了在终端上运行它，您需要为所有需要的 jar 指定类路径。
或者简单地在pom.xml中指定下面的maven插件来生成fat jar（带有依赖项的jar）并在运行时运行。

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-assembly-plugin</artifactId>
    <version>3.1.1</version>

    <configuration>
        <descriptorRefs>
            <descriptorRef>jar-with-dependencies</descriptorRef>
        </descriptorRefs>
    </configuration>

    <executions>
        <execution>
            <id>make-assembly</id>
            <phase>package</phase>
            <goals>
                <goal>single</goal>
            </goals>
        </execution>
    </executions>
</plugin>

希望这会有所帮助！

【讨论】：

我尝试了您的第二个解决方案，效果很好。谢谢！

【解决方案2】：

尝试使用包层次结构而不是 pega。希望它会有所帮助。

java - cp target/s_order_project-1.0-SNAPSHOT.jar com.example.pega

【讨论】：