Question

我在Flink 0.9中开发了一个使用图形模块（Gelly）的工作。作业在IDE（Eclipse）中成功运行，但在使用maven（mvn clean install）将其导出到JAR后，无法在本地flink实例上执行，并出现以下错误

“由于链接失败，无法加载程序的入口点类'myclass'”

java.lang.NoClassDefFoundError: org/apache/flink/graph/GraphAlgorithm

知道为什么会发生这种情况以及如何解决它？

Answer 1

看起来flink-gelly的代码没有在你的jar文件中结束。此问题最明显的原因是项目的pom文件中缺少maven依赖项。但我认为依赖存在，否则在IDE中开发工作是不可能的。

最有可能的是，jar文件是由maven-jar-plugin创建的，不包括依赖项。尝试将以下片段添加到pom.xml：

    <build>
    <plugins>
        <!-- We use the maven-shade plugin to create a fat jar that contains all dependencies
        except flink and it's transitive dependencies. The resulting fat-jar can be executed
        on a cluster. Change the value of Program-Class if your program entry point changes. -->
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-shade-plugin</artifactId>
            <version>2.3</version>
            <executions>
                <!-- Run shade goal on package phase -->
                <execution>
                    <phase>package</phase>
                    <goals>
                        <goal>shade</goal>
                    </goals>
                    <configuration>
                        <filters>
                            <filter>
                                <artifact>org.apache.flink:*</artifact>
                                <excludes>
                                    <exclude>org/apache/flink/shaded/**</exclude>
                                    <exclude>web-docs/**</exclude>
                                </excludes>
                            </filter>
                        </filters>
                        <transformers>
                            <!-- add Main-Class to manifest file -->
                            <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                                <mainClass>YOURMAINCLASS</mainClass>
                            </transformer>
                        </transformers>
                        <createDependencyReducedPom>false</createDependencyReducedPom>
                    </configuration>
                </execution>
            </executions>
        </plugin>
    </plugins>

</build>
<profiles>
    <profile>
        <!-- A profile that does everyting correctly:
        We set the Flink dependencies to provided -->
        <id>build-jar</id>
        <activation>
            <activeByDefault>false</activeByDefault>
        </activation>
        <dependencies>
            <dependency>
                <groupId>org.apache.flink</groupId>
                <artifactId>flink-java</artifactId>
                <version>0.9-SNAPSHOT</version>
                <scope>provided</scope>
            </dependency>
            <dependency>
                <groupId>org.apache.flink</groupId>
                <artifactId>flink-streaming-core</artifactId>
                <version>0.9-SNAPSHOT</version>
                <scope>provided</scope>
            </dependency>
            <dependency>
                <groupId>org.apache.flink</groupId>
                <artifactId>flink-clients</artifactId>
                <version>0.9-SNAPSHOT</version>
                <scope>provided</scope>
            </dependency>
        </dependencies>
    </profile>
</profiles>

现在，您可以使用mvn clean package -Pbuild-jar构建jar。 jar文件现在位于target/目录中。

您可以手动检查jar（zip）文件是否包含/org/apache/flink/graph/

中的类文件

运行Apache Flink作业时链接失败

1 个答案: