what to expect - jpa spec or impl discretion
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In reply to this post
by Beyer,Nathan
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In reply to this post
by Pinaki Poddar
The spec says in 3.6.1
"TheelementsoftheresultofaJavaPersistencequerywhoseSELECTclauseconsistsofmorethanone selectexpressionareoftypeObject[]" with apologies to those who prefer spaces in sentences. So the result of a SELECT MIN(e.sequence), MAX(e.sequence) should be an Object[] in which the first element is the MIN and the second element the MAX. If you use getResultList, then the result will be a List each element of which is an Object[2]. If you call getSingleResult, the result will be a single Object[2]. Craig On Jul 21, 2008, at 10:45 AM, Pinaki Poddar wrote: > > Hi, >> I'm a little confused by your example. You indicate that OpenJPA is >> returning an array of Objects? Did you mean that OpenJPA is >> returning a >> single Object? > > For results of native queries, OpenJPA returns a List. But each > member of > the list can be Object[] depending upon what has been selected by > the query > and @SQLResultSetMapping. > For example, a SQL > SELECT p.name, p.age FROM PERSON p WHERE p.age > 20 > > may select 42 rows. In that case, OpenJPA will return a List of 42 > elements where each element is a Object[] of length 2 with 0-th > element > being p.name and 1-st element is p.age. > > > > > Beyer,Nathan wrote: >> >> Re: the question about the return type of the native query >> >> To clarify, this is what I see in OpenJPA ... >> >> // LOG is table name with a 'sequence' column/field of Java type >> 'long' >> final Query query = entityManager.createNativeQuery("SELECT >> MIN(e.sequence), MAX(e.sequence) FROM LOG e"); >> >> If you use 'getResultList', then a List is return with one element, >> which >> is an Object[], so to process, you do this. >> final List result = query.getResultList(); >> final Object[] e0 = (Object[])result.get(0); >> final Number minSeq = (Number)e0[0]; >> final Number maxSeq = (Number)e0[1]; >> >> >> If you use 'getSingleResult', then just the Object[] is returned, >> so to >> process, you do this. >> final Object result = query.getSingleResult(); >> final Object[] e0 = (Object[])result; >> final Number minSeq = (Number)e0[0]; >> final Number maxSeq = (Number)e0[1]; >> >> >> >> -----Original Message----- >> From: Kevin Sutter [mailto:[hidden email]] >> Sent: Monday, July 21, 2008 12:01 PM >> To: [hidden email] >> Subject: Re: what to expect - jpa spec or impl discretion >> >> Nathan, >> Comments embedded below. This is just my interpretation of the >> spec (I am >> a >> member of the JPA expert group, but I am not the lead). Posting to >> the >> EclipseLink forum might be interesting as well... >> >> On Mon, Jul 21, 2008 at 10:15 AM, Beyer,Nathan <[hidden email]> >> wrote: >> >>> I'm trying to write a bit of code that's portable between JPA >>> providers >>> and >>> ran into a few differences and I'd like to know if they are >>> undefined >>> bits >>> of the spec or just me doing something silly. >>> >>> 1. 0 is considered null for primary key fields (@Id) of type >>> int, >>> long >>> - OpenJPA DOES NOT do this, but other providers, such as >>> EclipseLink do. >>> Is >>> this in the spec or up for debate? >> >> >> The spec does not identify valid values for a given annotation or >> field >> type. But, logic would say that 0 is a valid int or long and, thus, >> should >> be allowed as a primary key value. Of course, you could say that >> this >> wouldn't be a very solid value for a primary key, but it should be >> allowed >> in my book. >> >> >>> >>> 2. Return value of native queries is an Object[] or a List - >>> Consider >>> the following snippets >>> >>> // LOG is table name with a 'sequence' column/field >>> of >>> Java >>> type 'long' >>> final Query query = entityManager.createNativeQuery("SELECT >>> MIN(e.sequence), MAX(e.sequence) FROM LOG e"); >>> final Object result = query.getSingleResult(); >>> >>> With OpenJPA a Object[] is returned, in EclipseLink >>> a List >>> is returned. Is this defined anywhere? How can I define it. >> >> >> I'm a little confused by your example. You indicate that OpenJPA is >> returning an array of Objects? Did you mean that OpenJPA is >> returning a >> single Object? The JavaDoc for getSingleResult is like this: >> >> /** >> * Execute a SELECT query that returns a single result. >> * @return the result >> * @throws NoResultException if there is no result >> * @throws NonUniqueResultException if more than one result >> * @throws IllegalStateException if called for a Java >> * Persistence query language UPDATE or DELETE statement >> */ >> public Object getSingleResult(); >> >> So, I could see where someone might return a List (since it's an >> Object), >> but returning an array of Objects seems like a stretch. >> >> Given that, I would expect the result to be a single Object (not a >> List). >> If I wanted to process a List, then I would call getResultList. The >> example >> usage in the spec also supports this interpretation. >> >> Good luck with your comparisons, >> Kevin >> >> >>> >>> >>> Thanks, >>> -Nathan >>> >>> ---------------------------------------------------------------------- >>> CONFIDENTIALITY NOTICE This message and any included attachments >>> are from >>> Cerner Corporation and are intended only for the addressee. The >>> information >>> contained in this message is confidential and may constitute >>> inside or >>> non-public information under international, federal, or state >>> securities >>> laws. Unauthorized forwarding, printing, copying, distribution, or >>> use of >>> such information is strictly prohibited and may be unlawful. If >>> you are >>> not >>> the addressee, please promptly delete this message and notify the >>> sender >>> of >>> the delivery error by e-mail or you may call Cerner's corporate >>> offices >>> in >>> Kansas City, Missouri, U.S.A at (+1) (816)221-1024. >> >> > > -- > View this message in context: http://n2.nabble.com/what-to-expect---jpa-spec-or-impl-discretion-tp575285p575455.html > Sent from the OpenJPA Users mailing list archive at Nabble.com. > Architect, Sun Java Enterprise System http://java.sun.com/products/jdo 408 276-5638 mailto:[hidden email] P.S. A good JDO? O, Gasp! |
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