SqlTemplate | SqlTemplate 是sql模板引擎，主要解决动态拼接sql字符串

In Cayenne you can't fetch a partial object. Or rather you can fetch it as long as its ID columns are present, but the object will be in a "hollow" state. Then whenever you try to read a property of such object, it will be lazily resolved from DB (exactly what you are observing). Partial object fetch feature was requested recently, so this may change soon.

Now you have two options:

• Use full objects (via ObjectSelect query instead of SQLTemplate assuming you are on 4.0 or newer), as most often than not you don't care about micro-optimizations.
• Use column select (ObjectSelect.columnQuery(..)), that will produce a result that is a List of Object[], where each array contains values of the specified columns for a single DB row.

In the former case you preserve the object model sacrificing some extra memory (and perhaps fetch speed), in the latter - you optimize your query, but work with raw data. Programming is often about trade-offs after all :)

I'm struggling to understand what you're trying to achieve here.

For a start you never define a here-string you just define $number as a string

A here-string would look like this

Neither MappedSelect nor SQLSelect support prefetches, which is an unfortunate omission (I'll follow up to fill this gap in Cayenne). You may have to switch to the older, less pretty, but totally functional SQLTemplate query that does:

You should set select.setFetchingDataRows(true) as by default SQLTemplate will try to convert result into data objects (DateInfo in your case). After this flag set query will return List and DataRow is a Cayenne internal extension of plain java.util.HashMap.

Reason for Cayenne to return null instead of an object is that PK field either not found in the result set or its value is NULL. In your case I think that Cayenne can't find PK in the result as it seems that it's defined as userid id DB and in Cayenne code I see it's USERID.

And please let me give you some general advise about your code. Creating ServerRuntime per request is not really effective solution, you should keep it as application singleton, see this question for details. Moreover ObjectSelect (or SelectQuery if you are using older version of Cayenne) is a better (and really more flexible) way of selecting objects.

You can use it like this: