log4j2項目打成jar包運行日志無法打印

maven項目中因為引入的有log4j2 在打成jar包 通過java -cp 命令運行時，引起下面這段錯誤，后果就是log日志無法打印。

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 是采用的插件式編程，當log4j2包編譯時，或者含有log4j2插件的包編譯時，會將需要加載的插件信息放在META-INF/org/apache/logging/log4j/core/config/plugins/Log4j2Plugins.dat這個文件中（包括官方logj42的原生插件），然后項目啟動的時候，log4j2會在各個jar包的META-INF目錄下掃描這個插件信息文件，然后去加載插件。但是當項目被打成一個jar包時，如果兩個不同的jar包中都有Log4j2Plugins.dat 這個文件，就會出現問題，其中一個文件會被另一個覆蓋，導致項目啟動的時候有一個文件中的插件不能被正常加載，導致報錯。

所以解決辦法有兩種，第一種是在項目編譯打包時排除這個文件，第二種是合並這些文件。
我在嘗試第二種時該問題還是沒能解決，但是用第一種就解決了。

下面分別說下兩種解決辦法：

一：

在打包插件中maven-shade-plugin 排除相關這個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 解決在打成jar包運行時日志無法打印的問題 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：添加個transformer合並Log4j2Plugins.dat文件即可，需要一個第三方的轉換器maven-shade-plugin.log4j2-cachefile-transformer 。本人在嘗試該方法時還是未能解決以上問題，估計是哪里沒配置好，該方法不行的話，建議使用第一種，簡單方便。

<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>