Persistence

I have written about other database migration frameworks before but in this article I’d like to cover the Liquibase framework in combination with WildFly as Java EE 7 compatible application server. In the following tutorial, we’re going to write a full Java EE 7 book store application with a few steps and with Liquibase on board to create the database structure and insert example data into the database. Thanks to the WildFly Maven Plug-in we even do not need to download and configure the application server but let Maven and the plug-in do the work for us. ...

Using the Java Persistence API and a decent persistence provider allows us to configure and fine-tune when and how the second level cache is used in our application. In the following short examples, we’re going to demonstrate those features written as JUnit test cases and running on a H2 in-memory database. Figure 1. Persistence Unit Configuration Setup First of all we need some basic setup to run the following examples .. we need to select a JPA persistence provider and database, create a persistence-unit configuration and an environment to run tests on an in-memory database. ...

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. ...

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… Arquillian Basics If you’ve never heard of the Arquillian framework before, please feel free to have a look at the Arquillian documentation or an article of mine: Arquillian Tutorial: Writing Java EE 6 Integration Tests and more... ...

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. ...

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. Dependencies I’m using Hibernate as persistence manager here and Derby as an easy to setup database. In the last step we’ll be writing a test that’s why we’ve added JUnit and Hamcrest. ...

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. Maven Dependencies Needed For simplicity’s sake am I going to use an HSQL database for persistence, in addition the dependencies for hibernate-entitymanager and hibernate-search (of course) should be added to your pom.xml ...

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.. ...

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.. Prerequisites Java 6 JDK Maven >= 2 If you’d like to take a look behind the scenes e.g. how entities are mapped in your database you could install a RDBMS of your choice .. or just use Derby/JavaDB that is bundled with the JDK 6 ...

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. Examples package testapp class User { String name int iq int age static namedQueries = { dumbUsers { int referenceIq = 60 lt 'iq' , referenceIq } nameStartsWith { letter -> like 'name', '${letter}%' } midAges { between('age', 20, 40) } } } // count dumb users println User.dumbUsers.count() // print amount of users, usernames starting with an 'a' User.nameStartsWith('a').count() ...