Category Archives: How To

How To Java Basics

Execute Around idiom in Java

November 28, 2020 – 5:33 pm

The Execute Around idiom is a pattern that allows you to wrap an action with some standard setup / tear down steps. Examples might include: Execute within a lock: acquire the lock, do the action, release the lock Resource handling: acquire the resource, do the action, close the resource Execute as a user: switch to read more »

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How To Java Basics

Reverse order a Stream in Java

October 23, 2020 – 5:11 pm

How do you reverse order a Stream in Java? There’s no obvious Stream.reverse() method. Is this an oversight in the API? Is there a workaround?

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Docker How To

Initialize a Windows container with an entrypoint script

May 26, 2020 – 8:14 pm

A popular Docker article describes a pattern to initialize stateful container data at runtime. The example uses a Shell script to run the initialization and then pass control to the container’s main command. We can use the same pattern to initialize a Docker Windows container.

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Docker How To Spring Boot

Deploying to Google Kubernetes Engine

March 15, 2020 – 3:41 pm

Previously we looked at building a Spring Cloud Data Flow on Kubernetes. As a follow up, we’re now looking at deploying to Google Kubernetes Engine. The great thing about Kubernetes you use exactly the same commands to manage a cluster on your laptop as on a server or cloud compute platform. Google has first class read more »

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Docker How To Spring Boot

Spring Cloud Data Flow on Kubernetes

February 29, 2020 – 12:02 pm

Spring Cloud Data Flow is a powerful tool for composing and deploying message driven data pipelines. It allows us to compose simple Spring Cloud Stream applications into complex processing pipelines. It also takes care of deploying these pipelines into Kubernetes or into Cloud Foundry. It’s powerful but has a lot of moving parts. It can read more »

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How To Web Technologies

Secrets in Google App Engine

April 27, 2019 – 3:56 pm

Google App Engine makes it easy to deploy NodeJS applications. The GAE Standard Environment and SDK support NodeJS out of the box. This makes Google App Engine a great choice ahead of competitors such as Heroku, AWS or Microsoft Azure. Unfortunately though, there’s no support for managing secrets in Google App Engine. When I deployed Dog n Bone to GAE, I found this single shortcoming the main source of complexity.

There are however some workarounds. None of them is particularly nice though.

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Docker How To

SSH into a Docker Container

November 30, 2018 – 5:03 pm

Just sometimes, it’s useful to SSH into a Docker Container. While docker exec or docker attach are usually sufficient to run commands in a container, sometimes you specifically need SSH. For example, to connect directly from a remote machine or when an application needs to run commands on your container. Most Docker images don’t come with the SSHd service installed so it is not possible to SSH to them. This post demonstrates how to install and run the SSHd service to an existing image so that you can connect to it.

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How To Testing

Unit test time based logic

October 23, 2018 – 7:57 pm

A standard unit testing problem is how to unit test code that has a dependency on dates or times. Consider a method that returns a greeting according to the time of day. If we were to call this method from a test fixture (say JUnit), it would return different values depending on when the test was run. This is not ideal. Unit tests should pass or fail consistently.

Here’s a simple solution for testing time based code.

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How To Testing

Test log4j2 with JUnit using a custom appender

April 29, 2018 – 6:57 pm

In previous articles, I’ve described how to test System.out with JUnit and how to test log4j with JUnit. This article describes how to test log4j2 logging with JUnit. This largely follows the same technique as testing log4j logging but using the the newer log4j2 APIs. Differences between log4j and log4j2 log4j2 follows a similar design read more »

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How To Testing

Test log4j with JUnit using a custom appender

January 15, 2018 – 8:21 pm

Following a recent article on how to Test System.out with JUnit, here’s a follow up on how to test log4J with JUnit. This article describes a technique to test log4J output in a JUnit test by adding a custom appender. This allows us to verify that log4j output contains expected Strings.

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