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Every software project includes a set of architecture decisions defining boundaries and constraints for further design and implementation. It’s important to document those decisions somehow or else a development team might not know which decisions where made and with which assumptions. Or they know the decision but are missing the context and the consequences and therefore decisions are blindly accepted or blindly changed. In the following short tutorial I will show how to structure architecture decisions in so called Architecture Decision Records and how to manage them with a simple tool named ADR-Tools. ...

When we need to investigate the cause for a dysfunctional Java application we have a plethora of tools available that on the one hand help us in gathering information, artifacts and statistics and on the other hand help us in processing this information and identifying possible problems. The following list of tools, snippets, workflows and information about specific artifacts could provide a starting point for analyzing such problems and covers topics like heap-dumps, thread-dumps, heap-histograms, heap-regions, garbage-collection-logs, hotspot-compiler/codecache-logs, debugging native-memory, tools for heap-dump-analysis, JVM unified logging and more.. ...

When writing test for applications that interact with Kafka brokers we often need to setup a decent environment including an instance of Kafka and ZooKeeper. Though Kafka ships with some classes for testing, setting up a simple testing environment is quite easier with the kafka-unit library that offers JUnit test rule support or a fast programmatic setup within no time. In the following short example, I’d like to show how create a simple setup using Maven, Surefire and kafka-unit. ...

A lot of features are already included in the Neo4j graph database system but sometimes we want to extends its capabilities and implement functions and procedures by ourselves that we may reuse. In the following tutorial I will demonstrate how to implement a procedure for Neo4j, how to write and run tests using JUnit and an embedded graph database and last but not least how to setup Neo4j with Docker and our stored procedure installed in no time. ...

Reactive Streams is an initiative trying to standardize asynchronous stream processing with non-blocking back-pressure. With Java 9, new classes in the java.util.concurrent.flow package offer a semantically equivalent counterpart to this standard that may be adopted by other frameworks. In the following short tutorial we’re implementing examples for reactive streams with Java 9 and the Flow API, with RxJava2, with Akka, with Reactor and finally there is an example in RxJava1, too though it does not follow the standard. ...

I have written about other software system analyzing and validation tools before but today I would like to introduce a new tool named jqAssistant that supports software architects, developers and analysts in a variety of tasks like analyzing given structures, validating architectural or quality constraints and generating reports. Therefore jqAssistant analyzes given projects or artifacts and stores the gathered information – that is enriched by a variety of existing plugin-ins – in a Neo4j graph database. ...

Communicating with identity and access management systems is a common task for many web-applications exposing secured resources. Keycloak is an open source software that provides not also such authorization services but also offers a lot of features from Single-Sign-On, Identity-Brokering, Social-Login, User-Federation, multiple client-adapters up to the administration console or support for protocols like OpenID, SAML, OAuth2, Kerberos and more. I will demonstrate how to integrate a Spring Boot web application with Keycloak and configure an authentication flow that requires a two-factor-authentication with user credentials and also one-time-passwords. ...

The Java Mission Control and the Java Flight Recorder allow us to capture run-time information from our Java applications without much overhead and aggregate profiling information. I have written down the commands that I’m using the most when profiling a Java application with this tool chain in the following article. Figure 1. Java Mission Control - Report Running Java Mission Control (JMC) We may start the JMC user interface shown above using the jmc command that is shipped with Oracle’s JRockit or Java (since Java 7 update 40). ...

On the one hand adding dependencies to a project is easy, on the other hand securing a project and checking for vulnerable dependencies is way harder. The OWASP dependency check plugin for Maven allows us to scan our project’s dependencies for know vulnerabilities. I will demonstrate its usage in the following short example. Figure 1. OWASP Vulnerability Report Dependencies We just need to add one plugin-dependency to our Mavenized project’s pom.xml. ...

Writing microbenchmarks for parts of our applications is not always easy – especially when the internals of the virtual machine, the just-in-time-compiler and such things are coming into effect. Java Microbenchmark Harness is a tool that takes care of creating JVM warmup-cycles, handling benchmark-input-parameters and running benchmarks as isolated processes etc. Now following a few short examples for writing microbenchmarks with JMH. Figure 1. Java JMH Microbenchmarks running in IntelliJ...