Mini Spring Tips Service

This program discovers, renders, and schedules tweets that provide mini Spring Tips, introducing new things in mini Twitter-sized Spring Tips. I keep the content for my mini Spring Tips in a Github repository, which this program monitors. I've configured a webhook from that repository so that this service reindexes each time there's an update there.

Previews

If you want to validate your tip.xml manifest, you can use the /tips/preview endpoint. It is locked down, however, to anyone but the users in your stb_users table.

Building

You can build the application in the usual way:

mvn clean package

If you want to build a new Docker image, then use the built-in support for Buildpacks:

mvn spring-boot:build-image

This application is configured to use the full Buildpack builder because it uses (Apache Batik, used for rendering SVG elements) that ultimately depends on Java's AWT subsystems.

Formatting

This program uses the Spring Boot JavaFormat Maven plugin to ensure that the source code has the same formatting regardless of both how someone edits and in which IDE they edit it. It'll break the build if code is committed without first running the formatting plugin. Thus, before committing every change, run:

mvn spring-javaformat:apply

Fonts

The program uses fonts that I am pretty sure that I can't share with others. I've encrypted an archive of the fonts and stored them in this Git repository. To unencrypt the archive, you'll need a salt and a password, which I've stored in my secrets manager in the developer-advocacy group in a secret note for spring tips bites.

If you want to change the fonts, you need to put them in to a .tar.gz archive, such that they are the files that result from the un-archiving. I used the following command to create the archive:

tar -c * | gzip -9 > fonts.tgz

Then I use the following Java code with Apache Commons Compress on the classpath to encrypt it:

  var encryptor = Encryptors.stronger(password, salt);
  var decryptedTgz = ... // the Resource pointing to fonts.tgz from above
  if (decryptedTgz.exists()) {
    log.debug("somebody needs to do some encrypting!");
    var bytes = this.encryptor.encrypt(FileCopyUtils.copyToByteArray(decryptedTgz.getInputStream()));
    var writtenEncryptedTgz = new File(this.outputDirectory, "fonts.tgz.encrypted");
    ResourceUtils.write(bytes, new FileSystemResource(writtenEncryptedTgz));
    log.debug("wrote the encrypted file to " + writtenEncryptedTgz.getAbsolutePath());
  }

Replace src/main/resources/fonts.tgz.encrypted with the newly encrypted archive, then git commit -am polish and git push.

Architecture

A component monitors a Git repository containing tip XML markup files. As new ones arrive, it schedules those for publication in a local database. Once a day, a local cron process goes through all the scheduled tips and sends them to the twitter service, which has its own scheduling component. The local scheduler should do so based on its own localdabase of scheduled dates, striving to release new content on a configurable basis.

The scheduling is an interesting problem. I imagine we'll have a database containing information about the outstanding tips:

tip_id      | date_scheduled   | date_created 
------------------------------------------------------
1             2022-12-01         2022-10-31
2             2022-12-03         2022-10-32
3             2022-12-05         2022-10-32
4             null               2022-10-32

Maybe we could accept a cron String and manually advance time until the CronTrigger matches? Suppose there are no outstanding unscheduled tips. So, we take today's date. Otherwise, we take the date of the tip scheduled furthest into the future. Take that date, truncate it to the date, then advance a Date day by day until the CronTrigger matches. Then use that date to schedule the next tip that's not been scheduled. Then

spring-tips / spring-tips-minis-api