fixes #2334 make convertEnvVars configurable to work with lower case …

config/src/main/java/com/networknt/config/ConfigInjection.java

@@ -52,6 +52,7 @@ public class ConfigInjection {
     private static final String SCALABLE_CONFIG = "config";
     private static final String EXCLUSION_CONFIG_FILE_LIST = "exclusionConfigFileList";
     private static final String ALLOW_DEFAULT_EMPTY = "allowDefaultValueEmpty";
+    private static final String CONVERT_ENV_VARS = "convertEnvVars";
 
     private static final Map<String, Object> exclusionMap = Config.getInstance().getJsonMapConfig(SCALABLE_CONFIG);
 
@@ -107,6 +108,10 @@ static String convertEnvVars(String input){
         if (input == null) {
             return null;
         }
+        if (exclusionMap.get(CONVERT_ENV_VARS) != null && !(Boolean)exclusionMap.get(CONVERT_ENV_VARS)) {
+            // only if the flag is set to false, then don't convert.
+            return input;
+        }
         return input.replaceAll("[^A-Za-z0-9]", "_").toUpperCase();
     }
 

config/src/main/resources/config/config.yml

@@ -29,3 +29,9 @@ decryptorClass: com.networknt.decrypt.AutoAESSaltDecryptor
 # would be negative impact on the application security. The following config will ensure that
 # null will be used when the default value is empty without stopping the server during the start.
 allowDefaultValueEmpty: true
+
+# For some operating systems, environment variable can be only upper case, to make sure they can
+# match the key defined in each config files, we can convert the env vars to upper case to match.
+# The default value is true, and it will cover most operating systems (Linux and Windows). Change
+# this value to false if you have lower or mix case environment variable names.
+convertEnvVars: true