Category Archives: Java

How to capture log events in tests with Log4j 2

Posted on November 2, 2022 by Mikael Ståldal

Sometimes you want to verify that your program actually logs what it is supposed to be logging. When using Apache Log4j 2 as logging framework, it can be done like this: Include this dependency (for Maven, adjust appropriately for other … Continue reading →

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How to run exec-maven-plugin only if a file is not up-to-date

Posted on July 30, 2019 by Mikael Ståldal

In my Maven build, I use exec-maven-plugin to run an external tool for Java code generation. In this case the flatbuffers compiler (flatc). By default, flatc always runs, so you always get a new .java file. This will always trigger … Continue reading →

Posted in Java, maven, programming | Comments Off on How to run exec-maven-plugin only if a file is not up-to-date

Objects vs. data structures

Posted on February 8, 2016 by Mikael Ståldal

Several popular statically typed programming languages, including C++, Java and C#, have a serious design flaw. They make no useful distinction between objects in the OOP sense and plain data structures. A plain data structure should only be a dumb … Continue reading →

Posted in Java, programming | 2 Comments

Typesafe’s Reactive Straw man

Posted on August 3, 2015 by Mikael Ståldal

In their quest to promote Reactive, Typesafe is beating up a straw man by portraying blocking I/O in a particularly stupid way which is rarely (if ever) done in practice. In a recent webinar, I found this slide which suggests … Continue reading →

Posted in Java, Linux, reactive | 1 Comment

Create a self-contained .jar file with Maven

Posted on October 26, 2014 by Mikael Ståldal

If you want to create a self-contained .jar file, with all library dependencies included, you can do it with Maven. Include this in your pom.xml: <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-assembly-plugin</artifactId> <version>2.4</version> <configuration> <archive> <manifest> <mainClass>com.yourcompany.youapp.Main</mainClass> </manifest> </archive> <descriptorRefs> <descriptorRef>jar-with-dependencies</descriptorRef> </descriptorRefs> … Continue reading →

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Running Jetty as a service in Ubuntu Linix

Posted on October 2, 2014 by Mikael Ståldal

Jetty is a popular open source Java application server. In order to run it as a service on a Linux server, they recommend using a horribly overcomplicated and quite fragile script. In Ubuntu server, there is a better way. Leverage … Continue reading →

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Don’t use large BLOBs in MySQL from Java

Posted on June 5, 2014 by Mikael Ståldal

The MySQL database can store large chunks of binary data (up to 1 GB) using the BLOB data types. However, this does not work well if you access the MySQL database from Java (or any other JVM based language) using … Continue reading →

Posted in database, Java | 3 Comments

Don’t use PipedOutputStream on Android

Posted on March 4, 2014 by Mikael Ståldal

I was using java.io.PipedOutputStream in an Android app. The app performed horribly bad. After doing some profiling, it turned out that the call to PipedOutputStream.write(byte[]) that was really slow. After digging into the Android source code, I discovered that PipedOutputStream.write(byte[]) … Continue reading →

Posted in Android, Java | 2 Comments

Using an embedded SQL database in Java web application

Posted on October 13, 2013 by Mikael Ståldal

You have a Java web application needing a relational SQL database. According to JavaEE conventions, you declare the DataSource in web.xml: <resource-ref> <res-ref-name>jdbc/DS</res-ref-name> <res-type>javax.sql.DataSource</res-type> <res-auth>Container</res-auth> </resource-ref> and then fetch it in code with (DataSource)new InitialContext().lookup(“java:comp/env/jdbc/DS”). Using Maven, Jetty and HSQLDB, … Continue reading →

Posted in Java, JavaEE, web | 3 Comments

Web application frameworks in Java

Posted on November 25, 2010 by Mikael Ståldal

When you know which type of web application you are to develop, it’s time to have a look at some possible choices. I have tried to categorize some modern and popular web application frameworks in Java. Simple server driven MVC … Continue reading →

Posted in AJAX, Java, JavaEE, web | 1 Comment