Posts Tagged ‘persistence’

Creating elegant, typesafe Queries for JPA, mongoDB/Morphia and Lucene using Querydsl

Thursday, February 13th, 2014

Querydsl is a framework that allows us to create elegant, type-safe queries for a variety of different data-sources like Java Persistence API (JPA) entities, Java Data Objects (JDO), mongoDB with Morphia, SQL, Hibernate Search up to Lucene.

In the following tutorial we’re implementing example queries for different environments – Java Persistence API compared with a JPQL and a criteria API query, mongoDB with Morphia and last but not least for Lucene.

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Arquillian Transaction Extension: Transaction Rollback for your Java EE Integration Tests

Sunday, June 16th, 2013

I really love Arquillian to run integration tests for my Java EE applications – especially when running on different containers – and I also love the Arquillian tool stack from Arquillian Drone to the Arquillian Persistence Extensions.

Today I’d like to share a short snippet how to achieve transaction rollbacks when testing an EJB in combination with Arquillian and the Arquillian Transaction Extension…

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Creating slim Database Projections using JPA2 Constructor Expressions

Sunday, April 14th, 2013

One common question that you may encounter one day when using object-relational-mapping in your application is how to slim down data that you’re retrieving from the persistence layer down to a specific subset for your use-case in an efficient manner and without using complex additional mapping frameworks. In some situations you might declare lazy loaded fields but another approach that I’d like to share with you here are JPA2 constructor expressions.

Constructor expressions allow us to create plain old java objects from the result of an JPA query. The advantage is that we may use different projections for different scenarios and without being managed, the POJOs might help us save some resources here.

In the following tutorial, we’re going to persist 100 book entities with multiple properties to an embedded database and we’re using constructor expressions afterwards to create smaller POJOs using a subset of the information available from each persisted book.

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Adding multiple EntityListeners to an Entity in JPA 2

Monday, February 25th, 2013

The ability to attach lifecycle events to an entity using simple annotations sometimes is a neat feature in the Java Persistence API.

The following short snippets demonstrate how to bind and trigger the different available lifecycle events using an embedded derby database and a bunch of annotations.

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Hibernate Search Faceting: Discrete and Range Faceting by Example

Monday, March 26th, 2012

In today’s tutorial we’re exploring the world of faceted searches like the one we’re used to see when we’re searching for an item on Amazon.com or other websites. We’re using Hibernate Search here that offers an API to perform discrete as well as range faceted searches on our persisted data.

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JPA Persistence and Lucene Indexing combined in Hibernate Search

Sunday, February 5th, 2012

Often we’re writing an application that has to handle entities that – on the one side need to be persisted in a relational database using standards like the Java Persistence API (JPA) and using frameworks like Hibernate ORM or EclipseLink.

On the other side those entities and their fields are often stored in a highspeed indexer like Lucene. From this situation arises a bunch of common problems .. to synchronize both data sources, to handle special data mapped in an entity like an office document and so on..

Hibernate Search makes this all a lot easier for us as we’re hopefully going to see in the following short tutorial…

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Object-relational Mapping using Java Persistence API / JPA 2

Monday, October 11th, 2010

Today we’re going to take a look at the world of object-relational Mapping and how it is done using the Java Persistence API by creating some basic examples, mapping some relations and querying objects using JPQL or the Criteria API..

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Named Queries in Grails 1.2

Tuesday, April 6th, 2010

They built a nice new feature in Grails 1.2 called “named queries“. Named queries can be defined in a domain class as static properties and support the criteria builder syntax. (more…)

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