dominikdorn.com

it took me a while to figure out how to copy files with scp to Home Assistant.

Go to “Settings” > “Add-Ons” > “Advanced SSH & Web Terminal”

Then switch to the “Configuration” Tab, change username to root and enable the sftp option, then click safe:

Restart your Home Assistant Installation.. after everything is up again, you should now be able to SCP/SFTP files to your Home Asistant.

In case you need to marry SBT + Artifactory with Jenkins Pipelines – and like me, you don’t want to post the Artifactory Credentials in a public accessible place on the Jenkins Agent, here comes your solution!

First, create a secret containing the username + token/password of the user that should be used by jenkins. In my case, this secret is called acme-jenkins-artifactory-access-token

Then, during your pipeline, get the secret in an environment variable and during the build, post it in a credentials.sbt in the current working directory. This way, sbt will pick up your credentials and uses them to authenticate against your Artifactory to resolve artifacts.

Alternatively you could also create a “secret file” which already has the contents I’m here creating during the build and then just copy that to the current working dir. As I don’t want to create yet another secret containing the same credentials, I’ve chosen this approach.

At my current task, I had to make sure a native library is able to be loaded. I didn’t want to adjust the parameters of the JVM for this, so I had to patch the java.library.path at runtime.

This post is inspired by this post

So, this code (in Scala, but its quite similar in Java) consists of two parts:

1. Getting the current value of the java.library.path system property
2. Making sure its actually used by the JVM by doing some reflection hacky stuff.

Getting the current value of the java.library.path system property L7-16

This is straightforward. We do a System.getProperty and then just retrieve it, check if the path we want to add is already there or not. If not, we add it and then set the property.

Making sure its actually used by the JVM L18-23

This is the tricky part. We have to use reflection to get access to the sys_path field of the Classloader. This is usually set to the path where the RT.jar file is located. We make the field accessible, get its current value, then set it to null and set it back to its previous value. Changing the fields value actually triggers the reloading of the paths’, so that the java.library.path variable is read again and used from now on.

Compared to the inspiration post by Fahd Shariff, we make sure to set the sys_paths field back to a reasonable value, else the JVM is unable to use other native-functions, e.g. `java.nio` and you would get errors like:

[info] java.lang.ExceptionInInitializerError
[info] 	at java.base/sun.nio.fs.UnixFileSystemProvider.copy(UnixFileSystemProvider.java:258)
[info] 	at java.base/java.nio.file.Files.copy(Files.java:1295)
[info] 	at com.acme.calculation.demo.GamsIntegrationSpec.$anonfun$new$52(GamsIntegrationSpec.scala:278)
[info] 	at zio.internal.FiberContext.evaluateNow(FiberContext.scala:361)
[info] 	at zio.internal.FiberContext.$anonfun$evaluateLater$1(FiberContext.scala:775)
[info] 	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
[info] 	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
[info] 	at java.base/java.lang.Thread.run(Thread.java:834)
Code language: PHP (php)

Recently I had to push in a Jenkins Pipeline to a git repository that was only accessible through https with username + password.

Attempts to provide the password in the url like https://user:p@s$w0rd@host.com/ failed, as apparently the password contained already a @ character and thus messed up the url.

A good colleague pointed me to .netrc which apparently is used, as git itself is using curl under the covers. The only problem was, that – from what is publicly documented – the .netrc file has to be in the $HOME folder, which would mean, that all other jobs on the Jenkins instance could also use our credentials.. while in theory possible, its a NOGO in our situation.

In the end, I’ve ended up with this solution.

1. retrieving the credentials to be used and store them in an environment variable
2. create a local .netrc file in the project directory
3. then, when using git, override the $HOME variable and set it to the current directory (pwd), thus making git treat the current directory as the users home and look here for the .netrc file instead of the real home, which could be accessed by other users.

When you’re using PostgreSQL together with Slick, chances are high, that you’re also using the Slick-PG library. You probably came to this post, because you try to map your custom ADT to a List/Sequence of that and want to store it as a text[] (or other array) in PostgreSQL. When trying to do so, the compiler gave you an error like:

could not find implicit value for parameter tt: slick.ast.TypedType[List[xxx.UseCase]]

You already tried creating a MappedColumnType[UseCase, String], but for some reason, Slick hasn’t picked it up / is not using it for Sequences / Lists.

Go no further, the solution is near!

Simply create a new JdbcType[List[YourType]] based on the SimpleArrayJdbcType[String] and then use the mapTo[YourType] method.

I hope you found this helpful!

As I repeatedly (e.g. every 2nd year) have to find the right code to generate a HMAC SHA256 hash from a string, I’m sharing this (for me and others) here. The tricky part is the String-Format to 64 chars. Most code I’ve found had this set to 32 chars (like used for MD5) which resulted in too short hashes for certain inputs.

I hope you find this useful!

This is mainly a note to self on how to build inheritance hierarchies (e.g. Animal -> [Cat / Dog] ) with Play-JSON.

Documentation can be found here:

• Play-JSON
• Akka-Http Play-Json

As mentioned in my previous articles about using VAVR together with Spring, use the following classes to make VAVRs Option and all Collection types based on Seq work correctly with SpringDoc. Just place them in a package that gets scanned by Spring!

A big shoutout to bnasslahsen who provided me with the VavrOptionSupportConverter that I adjusted to work with the collection types (see this issue)