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From Steve Wells <websyst...@gmail.com>
Subject EJBQL with aggregrate function render to Java List
Date Tue, 12 Jan 2010 01:42:31 GMT
Hi All,

I have an EJBQL query selecting a grouped value from a master table
(Category.name) and the count of detail rows for each grouping (ie count of
the Category.questions), so I get results:
cat1, 5
cat2, 3
cat3, 10
etc...

Ideally what I need to do is get the results into a java List<?>, so I was
hoping (by waving magic Cayenne wand!) that this would work:

"select new CategorySummary(c.name, count(q)) from Category c left join
c.questions q group by c.name" returning a List<CategorySummary>...but I
can't get it working.  Is there a prescribed approach for this?

At the moment I get this:

java.lang.NullPointerException
	at org.apache.cayenne.ejbql.parser.Compiler.compileEntityResult(Compiler.java:219)
	at org.apache.cayenne.ejbql.parser.Compiler.compile(Compiler.java:200)
	at org.apache.cayenne.ejbql.parser.EJBQL$EJBQLDefaultParser.compile(EJBQL.java:30)
	at org.apache.cayenne.query.EJBQLQuery.getExpression(EJBQLQuery.java:122)
	at org.apache.cayenne.query.EJBQLQueryMetadata.resolve(EJBQLQueryMetadata.java:38)
	at org.apache.cayenne.query.EJBQLQuery.getMetaData(EJBQLQuery.java:66)
	at org.apache.cayenne.util.ObjectContextQueryAction.<init>(ObjectContextQueryAction.java:79)
	at org.apache.cayenne.access.DataContextQueryAction.<init>(DataContextQueryAction.java:48)
	at org.apache.cayenne.access.DataContext.onQuery(DataContext.java:1278)
	at org.apache.cayenne.access.DataContext.performQuery(DataContext.java:1267)
	at org.apache.click.extras.cayenne.CayenneTemplate.performQuery(CayenneTemplate.java:276)



CategorySummary.java:

CategorySummary {
    private String name;
    private Number count;

plus getters and setters

The EJB spec says you can do something like:

SELECT NEW com.acme.example.CustomerDetails(c.id, c.status, o.count)
FROM Customer c JOIN c.orders o
WHERE o.count > 100

Does Cayenne support this?

Thanks for any help,

Steve

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