flink error Hadoop is not in the classpath/dependencies.

1. 在 $FLINK_HOME/lib 下加 Hadoop 的jar包，官网可以下载 https://flink.apache.org/downloads.html

2. mvn 添加依赖：

<dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-client</artifactId>
            <version>${hadoop.version}</version>
        </dependency>