fix logger command do not work with Log4j2. ##1394 #1395

core/src/main/java/com/taobao/arthas/core/command/logger/Log4j2Helper.java

@@ -19,8 +19,6 @@ import org.apache.logging.log4j.core.appender.FileAppender;
 import org.apache.logging.log4j.core.config.Configuration;
 import org.apache.logging.log4j.core.config.LoggerConfig;
 
-import com.taobao.arthas.core.util.StringUtils;
-
 /**
  * 
  * @author hengyunabc 2019-09-20
@@ -96,7 +94,7 @@ public class Log4j2Helper {
                 return loggerInfoMap;
             }
             // 排掉非root时，获取到root的logger config
-            if (!name.equalsIgnoreCase(LoggerConfig.ROOT) && StringUtils.isEmpty(loggerConfig.getName())) {
+            if (!name.equalsIgnoreCase(LoggerConfig.ROOT) && isEmpty(loggerConfig.getName())) {
                 return loggerInfoMap;
             }
             loggerInfoMap.put(name, doGetLoggerInfo(loggerConfig));
@@ -190,4 +188,7 @@ public class Log4j2Helper {
         return result;
     }
 
+    private static boolean isEmpty(Object str) {
+        return str == null || "".equals(str);
+    }
 }