src/jdk.packager/share/classes/jdk/packager/internal/DeployParams.java

*** 566,588 ****
              StandardBundlerParam.ARGUMENTS.getID(),
              StandardBundlerParam.MODULE_PATH.getID(),
              StandardBundlerParam.ADD_MODULES.getID(),
              StandardBundlerParam.LIMIT_MODULES.getID(),
              StandardBundlerParam.STRIP_NATIVE_COMMANDS.getID(),
              JLinkBundlerHelper.DETECT_MODULES.getID()
      ));
  
      @SuppressWarnings("unchecked")
      public void addBundleArgument(String key, Object value) {
          // special hack for multi-line arguments
!         if (multi_args.contains(key) && value instanceof String) {
              Object existingValue = bundlerArguments.get(key);
!             if (existingValue instanceof String) {
                  bundlerArguments.put(key, existingValue + "\n\n" + value);
!             } else if (existingValue instanceof List) {
!                 ((List)existingValue).add(value);
!             } else if (existingValue instanceof Map && ((String)value).contains("=")) {
                  String[] mapValues = ((String)value).split("=", 2);
                  ((Map)existingValue).put(mapValues[0], mapValues[1]);
              } else {
                  bundlerArguments.put(key, value);
              }
--- 566,590 ----
              StandardBundlerParam.ARGUMENTS.getID(),
              StandardBundlerParam.MODULE_PATH.getID(),
              StandardBundlerParam.ADD_MODULES.getID(),
              StandardBundlerParam.LIMIT_MODULES.getID(),
              StandardBundlerParam.STRIP_NATIVE_COMMANDS.getID(),
+             StandardBundlerParam.FILE_ASSOCIATIONS.getID(),
              JLinkBundlerHelper.DETECT_MODULES.getID()
      ));
  
      @SuppressWarnings("unchecked")
      public void addBundleArgument(String key, Object value) {
          // special hack for multi-line arguments
!         if (multi_args.contains(key)) {
              Object existingValue = bundlerArguments.get(key);
!             if (existingValue instanceof String && value instanceof String) {
                  bundlerArguments.put(key, existingValue + "\n\n" + value);
!             } else if (existingValue instanceof List && value instanceof List) {
!                 ((List)existingValue).addAll((List)value);
!             } else if (existingValue instanceof Map &&
!                 value instanceof String && ((String)value).contains("=")) {
                  String[] mapValues = ((String)value).split("=", 2);
                  ((Map)existingValue).put(mapValues[0], mapValues[1]);
              } else {
                  bundlerArguments.put(key, value);
              }