报错现象：
Exception in thread "main" java.lang.NoClassDefFoundError: Lorg/apache/hadoop/fs/FileSystem;
at java.lang.Class.getDeclaredFields0(Native Method)
at java.lang.Class.privateGetDeclaredFields(Class.java:2583)
at java.lang.Class.getDeclaredFields(Class.java:1916)
at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:72)
at org.apache.flink.streaming.api.environment.StreamExecutionEnvironment.clean(StreamExecutionEnvironment.java:1560)
at org.apache.flink.streaming.api.datastream.DataStream.clean(DataStream.java:185)
at org.apache.flink.streaming.api.datastream.DataStream.addSink(DataStream.java:1191)
at KafkaHadoop.main(KafkaHadoop.java:46)
Caused by: java.lang.ClassNotFoundException: org.apache.hadoop.fs.FileSystem
at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
... 8 more
报错背景：
当时我是在做kafka+flink+hadoop数据存取的功能，一直在报这个错，代码也没有问题，困扰了很长时间。
报错解决：
第一步：我怀疑是依赖冲突问题，于是将关于hadoop的pom依赖给一一注释掉，发现做完之后还是报错；
第二步：我开始怀疑是没有这个jar包，但是当我去MVNREPOSITORY网站搜索关于org.apache.hadoop.fs.FileSystem的依赖时，搜索到了一下几个依赖：
hadoop-hdfs、flink-connector-filesystem_2.11、flink-hadoop-fs 相关的，但是放上去之后发现并没有什么卵用；
第三步：于是我就开始百度 org.apache.hadoop.fs.FileSystem 相关信息，
（1）找到了下面这个网站入口：
（2）点进去发现：
（3）然后点了进去：
虽然看不懂，但是我感觉很有可能就是在下面这几个jar包中，于是我就去MVNREPOSITORY网站搜索hadoop-core,
<!-- https://mvnrepository.com/artifact/org.apache.hadoop/hadoop-core -->
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-core</artifactId>
<version>1.1.0</version>
</dependency>
将这个依赖加了进去，然后报错解决。
完整pom：
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion> <groupId>yk.bigdate</groupId>
<artifactId>flinkHDFS</artifactId>
<version>1.0-SNAPSHOT</version> <properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<flink.version>1.6.1</flink.version>
<slf4j.version>1.7.7</slf4j.version>
<log4j.version>1.2.17</log4j.version>
</properties> <dependencies>
<!--******************* flink *******************-->
<dependency>
<groupId>org.apache.flink</groupId>
<artifactId>flink-java</artifactId>
<version>${flink.version}</version>
</dependency>
<dependency>
<groupId>org.apache.flink</groupId>
<artifactId>flink-streaming-java_2.11</artifactId>
<version>${flink.version}</version>
</dependency>
<!-- <dependency>
<groupId>org.apache.flink</groupId>
<artifactId>flink-clients_2.11</artifactId>
<version>${flink.version}</version>
</dependency>-->
<dependency>
<groupId>org.apache.flink</groupId>
<artifactId>flink-connector-kafka-0.11_2.11</artifactId>
<version>${flink.version}</version>
<scope> compile</scope>
</dependency>
<dependency>
<groupId>org.apache.flink</groupId>
<artifactId>flink-connector-filesystem_2.11</artifactId>
<version>${flink.version}</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.hadoop/hadoop-core -->
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-core</artifactId>
<version>1.1.0</version>
</dependency>
<!--******************* kafka *******************-->
<dependency>
<groupId>org.apache.kafka</groupId>
<artifactId>kafka-clients</artifactId>
<version>1.1.1</version>
</dependency> </dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.3</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
<!--打jar包-->
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<configuration>
<archive>
<manifest>
<mainClass>com.allen.capturewebdata.Main</mainClass>
</manifest>
</archive>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
</configuration>
</plugin>
</plugins>
</build>
</project>