Hi Dave,
By "object context" you don't mean ObjectContext, but rather the type of the
result, right?
If you need to determine result type dynamically, you can look at query
metadata:
QueryMetadata md = query.getMetaData(context.getEntityResolver());
List<Object> rsMapping = md.getResultSetMapping();
The returned list contains instances of EntityResultSegment or
ScalarResultSegment, so you ca make sense of the result format. Not sure if
this was your question here?
Andrus
On Mar 22, 2011, at 6:43 AM, Dave Mansfield wrote:
> Hello -
>
> I'm having a tough time understanding how to use the ResultItator properly.
> Reading the 3.0.1 Javadocs, it reports:
>
> Result "rows", depending on the query, may be represented as scalar values,
> DataRows, or Object[] arrays containing a mix of scalars and DataRows.
>
> In the performance tuning example, the guide shows:
>
> // ResultIterator operations all throw checked CayenneException
> try {
> // special "performIteratedQuery" method is used
> it = context.performIteratedQuery(q);
>
> while(it.hasNextRow()) {
> // ResultIterator always returns data rows Map row = (Map)
> it.nextRow();
> // do something with the row...
> ...
> }
> }
>
>
> How can one pre-determine the object context being returned from a
> ResultIterator.nextRow() call? My code depends on a base class applying
> object-specific behavior to serialize queries to another context.. One pass a
> scalar is returned; yet another pass I have a Map returned..
>
> Tks!
>
> Code snippet:
>
> ResultIterator resultIter = null;
> query.setPageSize(mPageSize);
> query.setFetchingDataRows(true);
> long rowCnt = 0;
> try {
> resultIter = mDataCtx.performIteratedQuery(query);
> } catch (CayenneException e) {
> mLogger.log(Level.FATAL, "Query failed!", e);
> return;
> }
> boolean needHeader = true;
> try {
> while ( resultIter.hasNextRow() ) {
> DataRow row = (DataRow)resultIter.nextRow();
> rowCnt++;
> if ( needHeader ) {
> this.writeHeader(row, errors);
> }
> this.writeLine(row, errors);
> }
> resultIter.close();
> } catch (CayenneException e) {
> mLogger.log(Level.FATAL, "Iterating through query failed!", e);
> return;
> }
> finally {
> try { if ( resultIter != null ) { resultIter.close(); } } catch
> (CayenneException e) { /* nothing */ }
> }
> }
>
>
