LinkageError解决

思路参考这个回答
在解决依赖冲突的场景中，偶尔会遇到这个问题：

java.lang.LinkageError: loader constraint violation: when resolving method "org.slf4j.impl.StaticLoggerBinder.getLoggerFactory()Lorg/slf4j/ILoggerFactory;" the class loader (instance of org/apache/catalina/loader/WebappClassLoader) of the current class, org/slf4j/LoggerFactory, and the class loader (instance of org/apache/catalina/loader/StandardClassLoader) for resolved class, org/slf4j/impl/StaticLoggerBinder, have different Class objects for the type taticLoggerBinder.getLoggerFactory()Lorg/slf4j/ILoggerFactory; used in the signature
at org.slf4j.LoggerFactory.getILoggerFactory(LoggerFactory.java:299)
at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:269)
at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:281)

显然，这是log4j的依赖冲突，但是通过idea的Mavendependency Analyzer并没有找到冲突的依赖，想办法排依赖可能就解决了。然而这种解决方式并不靠谱。这里把问题出现的原因和解决流程记录一下。

排查流程

这个问题是ILoggerFactory这个类被加载了两次

1. 在jvm参数里添加 -verbose:class， 打印类的加载路径
   找到冲突的jar包

   [Loaded org.slf4j.ILoggerFactory from file:/Users/kunni/.m2/repository/org/slf4j/slf4j-api/1.7.30/slf4j-api-1.7.30.jar]
   ......
   [Loaded org.slf4j.ILoggerFactory from file:/Users/kunni/.m2/repository/org/apache/hive/hive-exec/2.3.8/hive-exec-2.3.8.jar]

   可以看到这个类在slf4j-api-1.7.30.jar和hive-exec-2.3.8.jar上都出现了，可以断定hive-exec-2.3.8.jar里包含了其他版本的slf4j依赖。
2. 通过反编译查看依赖版本
   通过jd-gui查看hive-exec-2.3.8.jar里包含的slf4j依赖版本
   
   发现两个版本确实是不一致的，想办法解决这个问题。

解决

1. 通过maven的依赖覆盖解决这个问题
2. 通过maven shade插件改名解决这个问题

   <plugin>
       <groupId>org.apache.maven.plugins</groupId>
       <artifactId>maven-shade-plugin</artifactId>
       <version>3.2.4</version>
       <executions>
           <execution>
               <phase>package</phase>
               <goals>
                   <goal>shade</goal>
               </goals>
               <configuration>
                   <artifactSet>
                       <includes>
                           <include>*:*</include>
                       </includes>
                   </artifactSet>
                   <relocations>
                       <relocation>
                           <pattern>org.slf4j..</pattern>
                           <shadedPattern>shade.org.slf4j.</shadedPattern>
                       </relocation>
                   </relocations>
               </configuration>
           </execution>
       </executions>
   </plugin>