Db on Micha Kops' Tech Notes

Using Throwaway Containers for Integration Testing with Java, JUnit 5 and Testcontainers.

Wed, 30 Jan 2019 00:00:00 +0100

A lot of boilerplate code is written when developers need to test their applications with different connected systems like databases, stream platforms and other collaborators.

Docker allows to handle those dependencies but there is still some glue code required to bind the container’s lifecycle and the configuration to the concrete integration test.

Testcontainers is a testing library that offers lightweight throwaway instances of anything able to run in a Docker container, with bindings to configure the specific containers and also provides wrappers to manage our own custom containers.

Using jetstreamDB as in-memory Database for Java

Sat, 30 Jun 2018 00:00:00 +0200

JetstreamDB is a in-memory database engine for Java that claims to be built for ultra-high speed and the ability of managing complex data structures by storing real Java objects instead of serializing data structures to other database specific formats.

In the following short example I would like to demonstrate how to create and read items from such a database by building a small article management sample app.

Creating and Providing HipChat Integrations with Atlassian Connect, Nodejs and Express

Tue, 18 Aug 2015 00:00:00 +0200

HipChat is Atlassian’s alternative to Slack and its solution to team collaboration chats. Atlassian Connect offers developer tools to bootstrap applications, connect to Atlassian’s cloud products with easy and in combination with HipChat’s REST APIs allows us to write integrations for such a chat server in no time.

In the following tutorial I’d like to show how to write an integration within a few steps using Atlassian Connect, Node.js and Express and how to connect the integration to a HipChat server.

Java EE 7 Database Migrations with Liquibase and WildFly

Thu, 31 Jul 2014 00:00:00 +0200

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.

Easy Database Migrations using Flyway, Java EE 6 and GlassFish

Sun, 28 Apr 2013 00:00:00 +0200

Database migrations often are a necessity in the application development and maintenance life-cycle.

Whenever we need to apply changes to the database structure, insert new data fragments and in doing so want to be sure that this all happens with some control and versioning.

The following tutorial shows how implement this for a simple Java EE 6 web application to be run on a GlassFish application server in a few quick steps using the Flyway framework, an eager initialized Singleton EJB and some Maven wiring.

Postgres Snippets

Mon, 01 Mar 2010 00:00:00 +0100

Get size of a table

SELECT pg_size_pretty(pg_total_relation_size('schemaname.tablename'));

Select unique combination of fields / tuples

SELECT DISTINCT ON(field1, field2) field1, field2
FROM thetable

Select rows where a combination of fields is not unique

SELECT columnA, columnB, count(*) AS count
FROM thetable
GROUP BY columnA, columnB
HAVING count(*) > 1

Search for rows with array containing value

Assuming, the field appointments has the type date[]

SELECT *
FROM mtable
WHERE appointments @> ARRAY['2023-09-19'::date]