Home » Author Archives: Lukas Eder (page 3)

Author Archives: Lukas Eder

Lukas is a Java and SQL enthusiast developer. He created the Data Geekery GmbH. He is the creator of jOOQ, a comprehensive SQL library for Java, and he is blogging mostly about these three topics: Java, SQL and jOOQ.

An Ingenious Workaround to Emulate Sum Types in Java

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Before I move on with the actual article, I’d like to give credit to Daniel Dietrich, author of the awesome Javaslang library, who has had the idea before me:                 @lukaseder try with a static method <T, T1 extends T, … Tn extends T> Seq<T> toSeq(T1 t1, …, Tn tn) { … } ...

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Dear API Designer. Are You Sure, You Want to Return a Primitive?

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Some APIs are set in stone. For instance, the JDK’s. Or public APIs, like the one between a database and a database client (e.g. JDBC). This makes designing such APIs rather difficult as a lot of thinking needs to be done prior to publishing an API. Which means that being defensive when designing the API is a good choice. One ...

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Using Oracle AQ via Java 8 Streams

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One of the most awesome features of the Oracle database is Oracle AQ: Oracle Database Advanced Queuing. The AQ API implements a full fledged, transactional messaging system directly in the database. In a classic architecture where the database is at the center of your system, with multiple applications (some of which written in Java, others written in Perl or PL/SQL, ...

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How to Detect Slow Queries with jOOQ

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Just now, we implemented a nice little feature in jOOQ’s code generator: https://github.com/jOOQ/jOOQ/issues/4974 It detects whenever the jOOQ code generator runs a slow query to reverse engineer schema meta information. Why? In our development and integration test environment, we don’t have huge schemas with all the different performance edge cases put in place. For instance, we don’t have 5000 Oracle ...

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How to Pattern-Match Files and Display Adjacent Lines in Java

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Recently, we’ve published our article about the awesome window function support in jOOλ 0.9.9, which I believe is some of the best additions to the library that we’ve ever done. Today, we’ll look into an awesome application of window functions in a use-case that is inspired by this Stack Overflow question Sean Nguyen: How to get lines before and after ...

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Use JUnit’s expected exceptions sparingly

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Sometimes, when we get pull requests for jOOQ or our other libraries, people change the code in our unit tests to be more “idiomatic JUnit”. In particular, this means that they tend to change this (admittedly not so pretty code): @Test public void testValueOfIntInvalid() { try { ubyte((UByte.MIN_VALUE) - 1); fail(); } catch (NumberFormatException e) {} try { ubyte((UByte.MAX_VALUE) + ...

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Impress Your Coworkers by Using SQL UNPIVOT!

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I’ve recently encountered a very interesting question on Stack Overflow by an unnamed user. The question was about generating a table of the following form in Oracle, using a table valued function: Description COUNT ------------------- TEST1 10 TEST2 15 TEST3 25 TEST4 50 The logic that should be implemented for the COUNT column is the following: TEST1: count of employees ...

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Reactive Database Access – Part 3 – Using jOOQ with Scala, Futures and Actors

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We’re very happy to continue our a guest post series on the jOOQ blog by Manuel Bernhardt. In this blog series, Manuel will explain the motivation behind so-called reactive technologies and after introducing the concepts of Futures and Actors use them in order to access a relational database in combination with jOOQ. Manuel Bernhardt is an independent software consultant with ...

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If Java Were Designed Today: The Synchronizable Interface

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Java has come a long way. A very long way. And it carries with it all the “junk” from early day design decisions. One thing that has been regretted time and again is the fact that every object (potentially) contains a monitor. This is hardly ever necessary and this flaw was corrected, finally, in Java 5, when new concurrency APIs ...

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2016 Will be the Year Remembered as When Java Finally Had Window Functions!

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You heard right. Up until now, the awesome window functions were a feature uniquely reserved to SQL. Even sophisticated functional programming languages still seem to lack this beautiful functionality (correct me if I’m wrong, Haskell folks). We’ve written tons of blog posts about window functions, evangelising them to our audience, in articles like: Probably the Coolest SQL Feature: Window Functions ...

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