Merge remote-tracking branch 'remotes/origin/dev_bugfix_ljj' into dev

# Conflicts:
#	epmet-commons/epmet-commons-tools/src/main/java/com/epmet/commons/tools/utils/EpmetRequestHolder.java

epmet-commons/epmet-commons-tools/src/main/java/com/epmet/commons/tools/utils/EpmetRequestHolder.java

@@ -49,7 +49,7 @@ public class EpmetRequestHolder {
     public static String getHeader(String headerName) {
         Map<String, String> stringStringMap = requestHeaderTtl.get();
         if (stringStringMap == null){
-            return StrConstant.EPMETY_STR;
+            return null;
         }
         return stringStringMap.get(headerName.toLowerCase());
     }