FrameWork on Architecture and Data Blog

ID generation with ORM's Table, Sequence or Identity strategy

Mon, 12 Jun 2017 00:00:00 +0000

In this blog post, I will discuss ID generation techniques using the Object Relation Mapping frameworks such as Hibernate, Toplink, ActiveRecord, Entity Framework. When using hibernate or any other ORM mapping framework. There is a need to generate primary key values for the “id” columns. These values can be generated by using IDENTITY, SEQUENCE or TABLE strategies. Generating custom values for primary keys or other values is a topic for another blog post.

Using liquibase to load data and ignore some columns

Mon, 15 May 2017 00:00:00 +0000

Loading data into tables is needed many times on projects to load test, Liquibase provides a method to load data into tables with lots of customization. In the example shown below, I’m loading zip code data with the following column layout

"Zipcode","ZipCodeType","City","State","LocationType","Lat","Long","Location","Decommisioned","TaxReturnsFiled","EstimatedPopulation","TotalWages"

Transactions using Groovy.SQL with Spring annotations and connection pools

Mon, 14 Jan 2013 00:00:00 +0000

When using Groovy with Spring framework, interacting with the database can be done using the Groovy.SQL class which provides a easy to use interface. When using Groovy.SQL, if we have a need to do transactions, we have the .withTransaction method that accepts a closure, to which we can pass in code to execute within the transaction. In our project since we were using spring already, using annotations to define transactions would be a great. Standard @Transactional annotations with Groovy.SQL will not work, since every place where the Groovy.SQL is used a new connection is acquired from the connection pool causing the database work to span multiple connections, which can result in dead-locks on the database. What we really want is that the database connection be the same across all invocations of Groovy.SQL with-in the same transaction started by the annotated method.

Hibernate weirdness with property names

Fri, 24 Oct 2008 00:00:00 +0000

Consider this Hibernate mapping

@Column(name = "qReferenceId")
public Long getQReferenceId() {
return qReferenceId;
}

Where qReferenceId is data provided to our application via a external reference, we do not have a QReference Object or Table for FK references. When trying to query this object using DetachedQuery, this Simple expression was used.

public List<Movie> findByQReferenceId(Long id) {
     final SimpleExpression matchesId = Property.forName("qReferenceId").eq(id);
    DetachedCriteria criteria = DetachedCriteria.forClass(Movie.class);
    criteria = criteria.add(matchesId);
    List<Movie> movies = (List<Movie>) getHibernateTemplate().findByCriteria(criteria);
    return movies;
}

When running this method, I kept getting errors shown below.