启动spark streaming失败，报错为：

原因: java.lang.NoClassDefFoundError: org/apache/spark/api/java/function/FlatMapFunction

解决：

在pom.xml里面，原配置

        <dependency>
            <groupId>org.apache.spark</groupId>
            <artifactId>spark-streaming_2.12</artifactId>
            <version>3.2.1</version>
            <scope>provided</scope>
        </dependency>

的

<scope>provided</scope>

删掉即可。变为：

        <dependency>
            <groupId>org.apache.spark</groupId>
            <artifactId>spark-streaming_2.12</artifactId>
            <version>3.2.1</version>
        </dependency>