JPA 2.1 with EclipseLink


Ahmed Bhaila
Dealer Profiles



JPA


  • Java API for Database Persistence and Reads
  • Implementation Versions: 1.0, 2.0, 2.1
  • Implementations


                                                          

Which Implementation to choose?





  • Supports implementation JPA 2.1
  • Support for Coherence Caching
  • Good community support


EclipseLink



Reference Implementation of JPA 2.0/2.1
Based off Oracle TopLink
Plays nice with Coherence
Performs better*
Fewer Bugs

JPA Benchmark




source: http://www.jpab.org/All/All/All.html

ORM Mapping - Today



Reviews with multiple visit reasons

Using JPA Collections


1. Using a Set
@ElementCollection(fetch=FetchType.LAZY)
	@CollectionTable(joinColumns=@JoinColumn(name="CNSMR_DLR_REV_ID"), name="CNSMR_VISIT_REAS")
	@Column(name="CNSMR_VISIT_REAS_TYP_CD",insertable=false,updatable=false)
	protected Set reasonsForVisit;

Result Set:

reasonsForVisit: ["SHOPNEW", "SHOPUSED", "SHOPSVC"]

More ORM Mapping



Reviews with Categorized Ratings

Using JPA Collections


2. Using Maps

@ElementCollection(fetch=FetchType.LAZY)
	@CollectionTable(joinColumns=@JoinColumn(name="CNSMR_DLR_REV_ID"), name="CNSMR_DLR_REVIEW_CTGY")
	@Column(name="DLR_REV_CTGY_RATE_NBR",insertable=false,updatable=false)
	@MapKeyColumn(name="DLR_REV_CTGY_TYP_CD")
	protected Map ratings;ResultSet:{category=OverallFacilities, value=4.0}
{category=CustomerService, value=4.0}
{category=QualityOfRepair, value=4.0}
{category=BuyingProcess, value=4.0}

Extended ON Clause

Find All Reviews with approved responses

select distinct R from Review R LEFT JOIN R.responses rr ON rr.status = 'APP' where R.dealerPartyId = :dealerPartyId

Where Exists

Find All Reviews where one of the reasons for visiting is coming in for Service and Repair

select CR from ConsumerReviews CR JOIN CR.reviews R JOIN R.ratings RA JOIN R.reasonsForVisit VR " +
		     		"LEFT JOIN R.responses rr ON rr.status = 'APP' where exists(select v from VisitReason v where v.visitReasonCode = 'SVCREPAIR' and v.reviewId = R.reviewId) " +
		     		"and CR.dealerPartyId = :dealerPartyId and R.status='APP' " +
		     		"ORDER BY R.overallRating DESC, R.submittedDate DESC 

JPA QueryHints


Can be used to customize or optimize queries
  • QueryHints.FETCH
  • QueryHints.LEFT_FETCH 
 query="select CR from ConsumerReviews CR JOIN CR.reviews R JOIN R.ratings RA LEFT JOIN R.responses rr ON rr.status = 'APP' where CR.dealerPartyId = :dealerPartyId and R.status='APP' ORDER BY R.submittedDate DESC",
	     hints={
	    		 @QueryHint(name=QueryHints.FETCH, value="CR.reviews"),
	    		 @QueryHint(name=QueryHints.LEFT_FETCH, value="CR.ratings"),
	    		 @QueryHint(name=QueryHints.LEFT_FETCH, value="CR.reviews.reasonsForVisit"),
	    		 @QueryHint(name=QueryHints.LEFT_FETCH, value="CR.reviews.ratings"),
	    		 @QueryHint(name=QueryHints.LEFT_FETCH, value="CR.reviews.responses"),
	     }
Other QueryHints
  • QueryHints.BATCH_SIZE - The number of keys in the "IN" clause
  • QueryHints.QUERY_RESULTS_CACHE - To Cache or not to Cache

Questions?


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