Add another option to process null bind list

[shelocks]

Current for this sql use BindList and StringTemplate4

@SqlQuery("select * from resource where app_id = :appId <if(resourceIds)> and resource_id in 
                     +"(<resourceIds>) <endif> "
@UseStringTemplateEngine 
List<Object> query(@Bind("appId") String appId,@Define("resourceIds") @BindList(value = "resourceIds", onEmpty = BindList.EmptyHandling.NULL) List<String> resourceIds)

when resourceIds input is null,the sql will render to

select * from resource where app_id=xxx and resource_id in (null)

but i want it render to

select * from resource where app_id=xxx

currently a workaround way is convert input null to a empty list，but not everyone invoke this method know this trick

can BindList.EmptyHandling add another option？we can process null list like this:

stmt.define(name, null); 

[leaumar]

I don't see how EmptyHandling would offer a solution here, that option only controls what the in (?) part should render to if the list is null or empty: in (null), in (), or an exception.

I'm not familiar with using StringTemplate, but it seems odd to me that it considers resourceIds truthy when it's null. Is that the root problem we should look at?

Does your code work when you pass in an emptyList() instead of null?

[shelocks]

but it seems odd to me that it considers resourceIds truthy when it's null. Is that the root problem we should look at?

StringTemplate evaluate like this:

expr	x undefined	x null	x=""	x=list len=0
<if(x)>y< endif>	""	""	y	""

Currently EmptyHandling value processed like:
EmptyHandling.VOID --> stmt.define("name","")
EmptyHandling.NULL --> stmt.define("name","null"), is null string,not null value
EmptyHandling.THROW --> throw a exception

Does your code work when you pass in an emptyList() instead of null?

yes.but everyone invoke this method need to know this trick(empty list will evaluated to false),and convert a null value to empty list

[leaumar]

Hmm, I think the reason we insert "null" instead of null is because it's a Map, where getting a non-existent key returns null, so putting any key with value null is pointless. We also have to put it as a string because this is in the context of templating, where we need the literal word "null" to show up in the query.