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Author Archives: Vlad Mihalcea

Vlad Mihalcea is a software architect passionate about software integration, high scalability and concurrency challenges.

A beginner’s guide to Hibernate Types

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The basic mapping concepts When learning Hibernate many like to jump to parent-child associations without mastering the object relation mapping basics. It’s very important to understand the basic mapping rules for individual Entities before starting modelling Entity associations. Hibernate types A Hibernate type is a bridge between an SQL type and a Java primitive/Object type.   These are the types ...

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The minimal configuration for testing Hibernate

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Introduction In my previous post I announced my intention of creating a personal Hibernate course. The first thing to start with is a minimal testing configuration. The examples are relevant for Hibernate 4. You only need Hibernate In a real production environment you won’t use Hibernate alone, as you may integrate it in a JEE or Spring container. For testing ...

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The data knowledge stack

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Concurrency is not for the faint-hearted We all know concurrency programming is difficult to get it right. That’s why threading tasks are followed by extensive design and code reviewing sessions. You never assign concurrent issues to inexperienced developers. The problem space is carefully analysed, a design emerges and the solution is both documented and reviewed. That’s how threading related tasks ...

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The simple scalability equation

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Queueing Theory The queueing theory allows us to predict queue lengths and waiting times, which is of paramount importance for capacity planning. For an architect this is a very handy tool, since queues are not just the appanage of messaging systems. To avoid system over loading we use throttling. Whenever the number of incoming requests surpasses the available resources, we ...

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Time to break free from the SQL-92 mindset

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Are you stuck in the 90s? If you are only using the SQL-92 language reference, then you are overlooking so many great features like: window functions MERGE TRUNCATE INSTEAD OF triggers Some test data In my previous article I imported some CSV Codahale metrics into PostgreSQL for further analysis. Our time series data consists of a total request count and ...

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How to import CSV data into PostgreSQL

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Introduction Many database servers support CSV data transfers and this post will show one way you can import CSV files to PostgreSQL. SQL aggregation rocks! My previous post demonstrated FlexyPool metrics capabilities and all connection related statistics were exported in CSV format. When it comes to aggregation tabular data SQL is at its best. If your database engine supports SQL:2003 ...

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Professional connection pool sizing

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Introduction I previously wrote about the benefits of connection pooling and why monitoring it is of crucial importance. This post will demonstrate how Flexy Pool can assist you in finding the right size for your connection pools. Know your connection pool The first step is to know your connection pool settings. My current application uses XA transactions, therefore we use ...

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Flexy Pool, reactive connection pooling

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Introduction When I started working on enterprise projects we were using J2EE and the pooling data source was provided by the application server. Scaling up meant buying more powerful hardware to support the increasing request demand. The vertical scaling meant that for supporting more requests we would have to increase the connection pool size accordingly. Horizontal scaling Our recent architectures ...

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The anatomy of Connection Pooling

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Introduction All projects I’ve been working on have used database connection pooling and that’s for very good reasons. Sometimes we might forget why we are employing one design pattern or a particular technology, so it’s worth stepping back and reason on it. Every technology or technological decision has both upsides and downsides, and if you can’t see any drawback you ...

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Maven and Java multi-version modules

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Introduction Usually, a project has a minimum Java version requirement and that applies to all of its modules. But every rule has its exceptions, as recently I stumbled on the following issue. One open source project of mine mandates Java 1.6 for most of its modules, except one requiring the 1.7 version. This happens when integrating external libraries having different ...

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