Category Archives: java

Prometheus and Spring Boot Health Checks

Posted on June 24, 2018 by Matthias

When trying to set up alerting for Spring Boot services with Prometheus, I discovered the synthetic “up” time series which is great for checking whether the monitoring system can reach my service instances. While this is a great thing, I also … Continue reading →

Posted in java | Tagged | 5 Comments

Spring Boot: Logging Failed Logins

Posted on April 18, 2017 by Matthias

In many applications it’s important to react to failed logins and other security-critical events, for example to log the failed login attempt to a file or to display a captcha after repeated failures. Spring-based applications come with a simple mechanism to … Continue reading →

Posted in java | Tagged , | 11 Comments

The Curse of Convenience Methods

Posted on February 5, 2017 by Matthias

In the old days, many Java APIs were fairly low level and pretty generic. You often had to explicitly select a concrete implementation, provide lots of parameters, and generally needed to know how things worked. This has changed in recent years – modern … Continue reading →

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Empty InputStream with Spring MVC

Posted on January 6, 2017 by Matthias

The other day, I was trying to build a simple batch upload interface for a Java web application running Spring Boot with Spring MVC on Apache Tomcat. But when I tried reading the InputStream in my controller, it was always empty. … Continue reading →

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Resolving JARs

Posted on March 20, 2016 by Matthias

Sometimes it’s useful to check whether a local JAR file is available from Maven Central, for example when converting an old build system to Maven. In many old systems, JARs aren’t named consistently and versioning info isn’t available. Fortunately, Maven … Continue reading →

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Normalizing Text in Java

Posted on October 10, 2015 by Matthias

Once in a while I see misguided attempts at normalizing text to make it suitable for use in URLs, file names, or other situations where a plain ASCII representation is desired. This can be tricky but with Java’s excellent Unicode … Continue reading →

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Installing Oracle’s JDK on Debian/Ubuntu

Posted on November 9, 2014 by Matthias

Due to licensing issues, Linux distributions don’t ship Oracle Java packages anymore. In many cases, that doesn’t matter since you can just use OpenJDK. But if you do need Oracle’s JDK, Debian packages are a bit more convenient than handling … Continue reading →

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Maven: Discovering Dependency Conflicts

Posted on August 30, 2014 by Matthias

Among other things, Maven’s dependency plugin displays the result of Maven’s dependency resolution mechanism. The output of the dependency:tree goal makes it easy to see where transitive dependencies come from. This week I discovered that recent versions of the plugin … Continue reading →

Posted in java | Tagged , , | 2 Comments