DDevelopment & Design

Abstract method in Enums

Did you know that you can do that? private static enum DynamicProperty { cacheManagerName { @Override void applyChange(final PropertyChangeEvent evt, final RuntimeCfg config) { config.cacheManagerName = (Str…

Did you know that you can do that?

private static enum DynamicProperty {

    cacheManagerName {
        @Override
        void applyChange(final PropertyChangeEvent evt, final RuntimeCfg config) {
            config.cacheManagerName = (String) evt.getNewValue();
        }
    },
    defaultCacheConfiguration {
        @Override
        void applyChange(final PropertyChangeEvent evt, final RuntimeCfg config) {
            LOG.debug("Default Cache Configuration has changed, previously created caches remain untouched");
        }
    };

    abstract void applyChange(PropertyChangeEvent evt, RuntimeCfg config);
}

I think it’s nice because it allows you to customize Enum’s behavior or perform other actions on use.

Piece of code taken from EhCache Configuration (line 118 and further).

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DDevelopment & Design

Grails render as JSON catch

One of a reasons your controller doesn't render a proper response in JSON format might be wrong package name that you use. It is easy to overlook. Import are on top of a file, you look at your code and everything seems to be fine. Except response is still not in JSON format.

Consider this simple controller:

class RestJsonCatchController {
def grailsJson() {
render([first: 'foo', second: 5] as grails.converters.JSON)
    }

def netSfJson() {
render([first: 'foo', second: 5] as net.sf.json.JSON)
    }
}

And now, with finger crossed... We have a winner!

$ curl localhost:8080/example/restJsonCatch/grailsJson
{"first":"foo","second":5}
$ curl localhost:8080/example/restJsonCatch/netSfJson
{first=foo, second=5}

As you can see only grails.converters.JSON converts your response to JSON format. There is no such converter for net.sf.json.JSON, so Grails has no converter to apply and it renders Map normally.

Conclusion: always carefully look at your imports if you're working with JSON in Grails!

Edit: Burt suggested that this is a bug. I've submitted JIRA issue here: GRAILS-9622 render as class that is not a codec should throw exception