报错：Exception in thread "main" java.lang.NoClassDefFoundError: Lorg/apache/hadoop/fs/FileSystem
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><span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">></span>yk.bigdate<span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">></span>flinkHDFS<span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">version</span><span style="color: rgba(0, 0, 255, 1)">></span>1.0-SNAPSHOT<span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">version</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">properties</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">project.build.sourceEncoding</span><span style="color: rgba(0, 0, 255, 1)">></span>UTF-8<span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">project.build.sourceEncoding</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">flink.version</span><span style="color: rgba(0, 0, 255, 1)">></span>1.6.1<span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">flink.version</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">slf4j.version</span><span style="color: rgba(0, 0, 255, 1)">></span>1.7.7<span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">slf4j.version</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">log4j.version</span><span style="color: rgba(0, 0, 255, 1)">></span>1.2.17<span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">log4j.version</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">properties</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">dependencies</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 128, 0, 1)"><!--</span><span style="color: rgba(0, 128, 0, 1)">******************* flink *******************</span><span style="color: rgba(0, 128, 0, 1)">--></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">dependency</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">></span>org.apache.flink<span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">></span>flink-java<span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">version</span><span style="color: rgba(0, 0, 255, 1)">></span>${flink.version}<span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">version</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">dependency</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">dependency</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">></span>org.apache.flink<span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">></span>flink-streaming-java_2.11<span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">version</span><span style="color: rgba(0, 0, 255, 1)">></span>${flink.version}<span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">version</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">dependency</span><span style="color: rgba(0, 0, 255, 1)">></span><!-- <dependency>
<groupId>org.apache.flink</groupId>
<artifactId>flink-clients_2.11</artifactId>
<version>${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><span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">dependencies</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">build</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">plugins</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">plugin</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">></span>org.apache.maven.plugins<span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">groupId</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">></span>maven-compiler-plugin<span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">version</span><span style="color: rgba(0, 0, 255, 1)">></span>3.3<span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">version</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">configuration</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">source</span><span style="color: rgba(0, 0, 255, 1)">></span>1.8<span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">source</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">target</span><span style="color: rgba(0, 0, 255, 1)">></span>1.8<span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">target</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">configuration</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">plugin</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 128, 0, 1)"><!--</span><span style="color: rgba(0, 128, 0, 1)">打jar包</span><span style="color: rgba(0, 128, 0, 1)">--></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">plugin</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">></span>maven-assembly-plugin<span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">artifactId</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">configuration</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">archive</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">manifest</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">mainClass</span><span style="color: rgba(0, 0, 255, 1)">></span>com.allen.capturewebdata.Main<span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">mainClass</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">manifest</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">archive</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">descriptorRefs</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"><</span><span style="color: rgba(128, 0, 0, 1)">descriptorRef</span><span style="color: rgba(0, 0, 255, 1)">></span>jar-with-dependencies<span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">descriptorRef</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">descriptorRefs</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">configuration</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">plugin</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">plugins</span><span style="color: rgba(0, 0, 255, 1)">></span> <span style="color: rgba(0, 0, 255, 1)"></</span><span style="color: rgba(128, 0, 0, 1)">build</span><span style="color: rgba(0, 0, 255, 1)">></span></project>