Infinite Loop when having any Enum type in a WebHandler

[rbanikaz]

We ran into a problem where snow 1.9.x will go into an infinite loop when we have a Enum type in the WebHandler method. This was working in the old snow.

The infinite loop occurs in WebParamResolverRegistry.getWebParamResolverRef:

       // if still null, then, check the parent classes
       if (ref == null){
            Class parentClass = paramType.getSuperclass();
            while (ref == null && parentClass != Object.class){
                ref = refByReturnType.get(parentClass);
            }
        }

Enum types do not extend from Object.class so this was being repeated and system would hang.

Resolved the issue by creating a WebParamResolver for java.lang.Enum:

 @WebParamResolver
    public Enum resolveEnum(AnnotationMap annotationMap, Class paramType, RequestContext rc) {
        WebParam webParam = annotationMap.get(WebParam.class);
        String val = rc.getParam(webParam.value());
        return Enum.valueOf(paramType, val);
    }

[jeremychone]

Very cool, you are correct, this slip through the crack. We will put this fix in 1.9.9.

Note: In the Snow implementation, we will not use Enum.valueOf as it throws exception when no match, but the default Snow WebParamResolver in these type of circumstance is to return null.

[rbanikaz]

In xadcms we use the following utility function to return null in that case:

 public static <T extends Enum<T>> T enumValueOf(Class<T> enumClass, String name) {
        try {
            return Enum.valueOf(enumClass, name);
        } catch(Exception e) {
            return null;
        }

    }

[jeremychone]

ObjectUtil.getValue(value,EnumClass) does the same. But good to have your own.

[jeremychone]

Fix in the main trunk. Will be available in 1.9.9.

@rbanikaz note that your fix will still run, since it will override the default system parser.