On May 18, 2010, at 9:57 AM, Jason Lee wrote:
> I'm currently working on getting a prototype running of the Admin Console using the REST API, and I'm having an issue with default values. Using AMX, when we ask the system for the default values for a JDBC Connection Pool, for steadyPoolSize, for example, we get 8. Via REST, we get null. I glanced at the AMX code, and it appears that it is asking JMX for the default value (how that works, specifically, I really don't know). The REST API returns the value of the "defaultValue" attribute on the Param annotation, which causes problems for us, as that value is not always specified.
>
> Looking that the class CreateJdbcConnectionPool, we see this code:
>
> @Param(name="steadypoolsize", camelCaseName = "steadyPoolSize", optional=true)
> String steadypoolsize = "8";
I think this is the wrong design pattern
it should be :
@Param(name="steadypoolsize", camelCaseName = "steadyPoolSize", optional=true, defaultValue="8")
String steadypoolsize;
and have the @Param injector takes care of "injecting" the fields with the annotation default value if the parameter was not specified on the command line.
should I implement that ?
jerome
>
> While defaultValue is not specified, there clearly exists a default, as steadypoolsize is initialized to 8 when an instance of the class is created.
>
> My question, then, is how should we handle this? Altering every Param instance to specify a default value would work, though it would be tedious, and, unless we then removed the initialization values on the ivars, we wouldn't be DRY, but removing that might break other code.
>
> Another approach might be to populate the defaultValue attribute automatically when CommandModel.getParameters() is called. Ultimately, that method call ends up calling CommandModelImpl.add():
>
> private void add(AnnotatedElement e) {
> if (e.isAnnotationPresent(Param.class)) {
> ParamModel model = new ParamModelImpl(e);
> if (!params.containsKey(model.getName())) {
> params.put(model.getName(), model);
> }
> }
> }
>
> It would probably be pretty trivial to check for null and populate if necessary here, but that would require instantiating an instance of the AdminCommand, which may involve side effects and/or performance issues that I can't predict as this is the first I've looked at the code this deeply. :)
>
> We could also put this second option at the REST layer, and query a live object every time the default values are needed, if this type of behavior is undesirable at the CommandModel level.
>
> Any thoughts? Other options I'm missing? For the prototype, I don't think this is a real blocker, but we'll certainly need a solution before we can begin the Console's AMX to REST migration in earnest.
>
> --
> Jason Lee
> Senior Member of Technical Staff
> GlassFish Administration Console
>
> Oracle Corporation
> Phone x31197/+1 405-343-1964
> Blog http://blogs.steeplesoft.com
>
>
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