解决java.lang.NoClassDefFoundError: io/netty/util/concurrent/GenericFutureListener

Given the information as follows:

[ERROR]Activator initialize error : websocket
[ERROR]io/netty/util/concurrent/GenericFutureListener
java.lang.NoClassDefFoundError: io/netty/util/concurrent/GenericFutureListener
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:264)
    ……
Caused by: java.lang.ClassNotFoundException: io.netty.util.concurrent.GenericFutureListener
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1363)
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1186)
    ... 45 more

Class not found, it should be the lack of dependence of this class can derive the corresponding dependent on it

https://mvnrepository.com/artifact/io.netty/netty-all

You can add

<!-- https://mvnrepository.com/artifact/io.netty/netty-all -->
<dependency>
    <groupId>io.netty</groupId>
    <artifactId>netty-all</artifactId>
    <version>5.0.0.Alpha2</version>
</dependency>

Pom files to or from the site to download the jar and add it to the class path or lib folder

Reproduced in: https: //www.jianshu.com/p/13bf0f0e1539