About Tomasz Nurkiewicz

Java EE developer, Scala enthusiast. Enjoying data analysis and visualization. Strongly believes in the power of testing and automation.

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Three flavours of request-response pattern in Akka

Imagine a simple Akka actor system consisting of two parties: MonitoringActor and NetworkActor. Whenever someone (client) sends CheckHealth to the former one it asks the latter by sending ...
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Turning Twitter4J into RxJava’s Observable

aTwitter4J is a Java wrapper around Twitter API. While Twitter supports simple request-response interactions in this article we will explore streaming APIs. In contrary to request-response ...
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Proxies done right with Guava’s AbstractInvocationHandler

Not too often but sometimes we are forced to write custom dynamic proxy class using java.lang.reflect.Proxy. There is really no magic in this mechanism and it’s worth knowing ...
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Playing with futures

During job interviews we often give Scala developers a simple design task: to model a binary tree. The simplest but not necessarily best implementation involves Option idiom:                 case ...
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instanceof operator and Visitor pattern replacement in Java 8

I had a dream where instanceof operator and downcasting were no longer needed but without clumsiness and verbosity of visitor pattern. So I came up with the following DSL syntax:                 Object ...
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Optional in Java 8 cheat sheet

java.util.Optional<T> in Java 8 is a poor cousin of scala.Option[T] and Data.Maybe in Haskell. But this doesn’t mean it’s not useful. If this concept is new to you, imagine ...
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Asynchronous retry pattern

When you have a piece of code that often fails and must be retried, this Java 7/8 library provides rich and unobtrusive API with fast and scalable solution to this problem:                   ScheduledExecutorService ...
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Managing congested actors in Akka

There comes a time in an Akka application when an actor can longer handle increasing load. Since each actor can only handle one message at a time and it keeps a backlog of pending messages ...
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Fake system clock pattern in Scala with implicit parameters

Fake system clock is a design pattern addressing testability issues of programs heavily relying on system time. If business logic flow depends on current system time, testing various ...
spring-interview-questions-answers

su and sudo in Spring Security applications

Long time ago I worked on a project that had a quite powerful feature. There were two roles: user and supervisor. Supervisor could change any document in the system in any way while ...
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