Author Archives: datanucleus

DN v5 : JPQL FROM JOIN to another “root” entity

A vendor extension now available in DataNucleus v5 is for JPQL’s ability to JOIN to other entities. In standard JPQL you can only add a JOIN through a relation. For example SELECT p FROM Person p JOIN p.address a WHERE … Continue reading

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JDO 3.2 JDOQLTypedQuery : improvements relative to DN extension

Now that JDO 3.2 standardises the “typed query” mechanism that we prototyped in DataNucleus v3.x and v4.0/v4.1 it is worth mentioning the additions to the API that are present in the JDO 3.2 variant. StringExpression This has gained the following … Continue reading

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JDO 3.2 JDOQLTypedQuery

JDO 3.2 is now standardising what we initially developed as a DataNucleus extension for JDO querying, namely typesafe queries. In DataNucleus upto and including v4.1 it was referred to as JDOQL Typesafe Query, and in JDO 3.2 (DataNucleus v4.2+) it … Continue reading

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JDO 3.2 Revisions to Query API

Here we present some changes to the JDO Query API that are coming in version 3.2 of the spec. Comments should be directed ASAP to the Apache JDO mailing list if you want any changes to make it in to … Continue reading

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JDO : querying between classes without relation

Let’s say we have the following classes and are using RDBMS for persistence public class Country { long id; String name; } public class Region { long id; String name; Long countryId; } public class District { long id; String … Continue reading

Posted in JDO, JDOQL | 10 Comments

Want to assist in the development of JDO 4.0?

We have, since 2006, been reliant on the Apache JDO project to push forward the JDO standard. Politics have finally become too much for this arrangement, with Oracle involving lawyers to prohibit progress, and the Apache organisation not being as … Continue reading

Posted in JDO, JDOQL | 7 Comments

Bytecode Enhancement contract in DataNucleus AccessPlatform v4.0

Now in GitHub master, for DataNucleus AccessPlatform v4.0, we have changed the bytecode enhancement contract. Since the days of JPOX we’ve always used the JDO bytecode enhancement contract as defined in the JDO spec. This has always been adequate to … Continue reading

Posted in Bytecode, JDO, JPA | 6 Comments

Configuring persistence of fields/properties using TypeConverters with JDO

JPA 2.1 allows a user to specify a converter on the value of a field/property for how it is persisted in the datastore. The way we implement that in DataNucleus is to have the JPA converter as a wrapper to … Continue reading

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AccessPlatform 3.3 and JPA 2.1

We will soon be releasing AccessPlatform 3.3. This is coming very soon after 3.2, and the reason for this is that it is simply AccessPlatform 3.2 plus full support for JPA 2.1 (i.e an upgraded datanucleus-api-jpa plugin). From that point … Continue reading

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What does open-source owe you?

If you ever embark on a period of time writing open source (free) software you’ll almost certainly come across many different attitudes in the people who choose to use this software. There will be some people who’ll actually say thanks … Continue reading

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