log4j2项目打成jar包运行日志无法打印

maven项目中因为引入的有log4j2 在打成jar包 通过java -cp 命令运行时，引起下面这段错误，后果就是log日志无法打印。

ERROR StatusLogger Unrecognized format specifier [d]
ERROR StatusLogger Unrecognized conversion specifier [d] starting at position 16 in conversion pattern.
ERROR StatusLogger Unrecognized format specifier [thread]
ERROR StatusLogger Unrecognized conversion specifier [thread] starting at position 25 in conversion pattern.
ERROR StatusLogger Unrecognized format specifier [level]
ERROR StatusLogger Unrecognized conversion specifier [level] starting at position 35 in conversion pattern.
ERROR StatusLogger Unrecognized format specifier [logger]
ERROR StatusLogger Unrecognized conversion specifier [logger] starting at position 47 in conversion pattern.
ERROR StatusLogger Unrecognized format specifier [msg]
ERROR StatusLogger Unrecognized conversion specifier [msg] starting at position 54 in conversion pattern.
ERROR StatusLogger Unrecognized format specifier [n]
ERROR StatusLogger Unrecognized conversion specifier [n] starting at position 56 in conversion pattern.
ERROR StatusLogger Reconfiguration failed: No configuration found for ‘5c647e05‘ at ‘null‘ in ‘null‘

先分析原因：

log4j2 是采用的插件式编程，当log4j2包编译时，或者含有log4j2插件的包编译时，会将需要加载的插件信息放在META-INF/org/apache/logging/log4j/core/config/plugins/Log4j2Plugins.dat这个文件中（包括官方logj42的原生插件），然后项目启动的时候，log4j2会在各个jar包的META-INF目录下扫描这个插件信息文件，然后去加载插件。但是当项目被打成一个jar包时，如果两个不同的jar包中都有Log4j2Plugins.dat 这个文件，就会出现问题，其中一个文件会被另一个覆盖，导致项目启动的时候有一个文件中的插件不能被正常加载，导致报错。

所以解决办法有两种，第一种是在项目编译打包时排除这个文件，第二种是合并这些文件。
我在尝试第二种时该问题还是没能解决，但是用第一种就解决了。

下面分别说下两种解决办法：

一：

在打包插件中maven-shade-plugin 排除相关这个Log4j2Plugins.dat即可
**/Log4j2Plugins.dat

<plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>3.0.0</version>
                <configuration>
                    <filters>
                        <filter>
                            <artifact>*:*</artifact>
                            <excludes>
                                <exclude>META-INF/*.SF</exclude>
                                <exclude>META-INF/*.DSA</exclude>
                                <exclude>META-INF/*.RSA</exclude>
                                <!-- 排除log4j2插件文件 解决在打成jar包运行时日志无法打印的问题 https://stackoverflow.com/questions/34945438/log4j2-configuration-not-found-when-running-standalone-application-built-by-shad-->
                                <exclude>**/Log4j2Plugins.dat</exclude>
                            </excludes>
                        </filter>
                    </filters>
                    <artifactSet>
                        <includes>
                            <include>*:*</include>
                        </includes>
                    </artifactSet>
                </configuration>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

二：添加个transformer合并Log4j2Plugins.dat文件即可，需要一个第三方的转换器maven-shade-plugin.log4j2-cachefile-transformer 。本人在尝试该方法时还是未能解决以上问题，估计是哪里没配置好，该方法不行的话，建议使用第一种，简单方便。

<plugin>
   <groupId>org.apache.maven.plugins</groupId>
   <artifactId>maven-shade-plugin</artifactId>
   <version>2.4.3</version>
   <executions>
       <execution>
           <phase>package</phase>
           <goals>
               <goal>shade</goal>
           </goals>
           <configuration>
               <filters>
                   <filter>
                       <artifact>*:*</artifact>
                       <excludes>
                           <exclude>META-INF/*.SF</exclude>
                           <exclude>META-INF/*.DSA</exclude>
                           <exclude>META-INF/*.RSA</exclude>
                       </excludes>
                   </filter>
               </filters>
               <finalName>${artifactId}-${env}-${version}</finalName>
               <transformers>
                  
                   <transformer
                           implementation="org.apache.maven.plugins.shade.resource.ServicesResourceTransformer"/>
                   <transformer implementation="com.github.edwgiz.mavenShadePlugin.log4j2CacheTransformer.PluginsCacheFileTransformer" />
               </transformers>
           </configuration>
       </execution>
   </executions>
   <dependencies>
       <dependency>
           <groupId>com.github.edwgiz</groupId>
           <artifactId>maven-shade-plugin.log4j2-cachefile-transformer</artifactId>
           <version>2.6.1</version>
       </dependency>
   </dependencies>
</plugin>