Home » Author Archives: Lukas Eder (page 11)

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.

Integrating jOOQ with Grails Featuring the UWS-jOOQ Plugin

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Introduction Grails is a web framework aimed to boost development productivity. One of the main features is domain centric database schema generation. Applications built with Grails are able to update existing schema just before they start. To do this, Grails is using built-in domain mappers or migrations in more advanced cases. The goal of the UWS-jOOQ Grails-plugin is to integrate ...

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The Java Legacy is Constantly Growing

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I’ve recently stumbled upon a very interesting caveat of the JDK APIs, the Class.getConstructors() method. Its method signature is this:                   Constructor<?>[] getConstructors() The interesting thing here is that Class.getConstructor(Class...) returns a Constructor<T>, with <T> being maintained: Constructor<T> getConstructor(Class<?>... parameterTypes) Why is there a difference, i.e. why doesn’t the first method return ...

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Avoid Recursion in ConcurrentHashMap.computeIfAbsent()

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Sometimes we give terrible advice. Like in that article about how to use Java 8 for a cached, functional approach to calculating fibonacci numbers. As Matthias, one of our readers, noticed in the comments, the proposed algorithm may just never halt. Consider the following program:               public class Test { static Map<Integer, Integer> cache ...

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How to use SQL PIVOT to Compare Two Tables in Your Database

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This can happen ever so easily. You adapt a table by adding a new column:                     ALTER TABLE payments ADD code NUMBER(3); You go on, implementing your business logic – absolutely no problem. But then, later on (perhaps in production), some batch job fails because it makes some strong assumptions about ...

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How to Extract a Date Part in SQL

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The Modern SQL Twitter account (by Markus Winand) published a hint about how to extract a date part in SQL:                     The right way to get a part of a date/time is: EXTRACT(YEAR FROM CURRENT_DATE) = 2015 http://t.co/UNLyUoQdVb Retweet to spread the word! — Modern SQL (@ModernSQL) February 24, 2015 Is it true? Yes ...

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jOOQ vs. Slick – Pros and Cons of Each Approach

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Every framework introduces a new compromise. A compromise that is introduced because the framework makes some assumptions about how you’d like to interact with your software infrastructure. An example of where this compromise has struck users recently is the discussion “Are Slick queries generally isomorphic to the SQL queries?“. And, of course, the answer is: No. What appears to be ...

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Thou Shalt Not Name Thy Method “Equals”

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(unless you really override Object.equals(), of course). I’ve stumbled upon a rather curious Stack Overflow question by user Frank: Why does Java’s Area#equals method not override Object#equals? Interestingly, there is a Area.equals(Area) method which really takes an Area argument, instead of a Object argument as declared in Object.equals(). This leads to rather nasty behaviour, as discovered by Frank:   @org.junit.Test ...

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“NoSQL Injection” – What 40000 Unsecured MongoDB Databases Mean for our Industry

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The news is all over reddit… Major security alert as 40,000 MongoDB databases left unsecured on the internet Security is a feature that is often neglected until it’s too late. And when it’s too late, it is often hard to bake it into a well-established architecture without major refactoring efforts. Every system and thus also every database is always vulnerable. ...

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10 SQL Articles Everyone Must Read

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We’ve been blogging about Java and SQL for a while now, on the jOOQ blog. Over the years, while researching interesting blog topics, we’ve discovered a lot of SQL gems in the blogosphere that have inspired our work and our passion for SQL. Today, we’re presenting to you a list of 10 articles that we think you should absolutely read. ...

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Top 10 Easy Performance Optimisations in Java

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There has been a lot of hype about the buzzword “web scale“, and people are going through lengths of reorganising their application architecture to get their systems to “scale”. But what is scaling, and how can we make sure that we can scale? Different aspects of scaling The hype mentioned above is mostly about scaling load, i.e. to make sure ...

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