Approaches

• Twelve-factor app

JDKs

JDK is a development environment (compiler, jvm, debugger) JRE is just executable runtime (java command)

There are many JDK distributions

Versions

• Before: no language features
• 8: F
• 11: D
• 17: C
• 19:
• 21:
• 23: S good performance

Gradle

• Groovy/Kotlin DSL

Migrations

Can be run as jobs from ci or a ceprate service, on application start Can run as mvn or gradle plugins Use liquibas

Maven

• XML
• too hard practically

Spring

• Spring-boot is preconfigured
• supports dependency injection

Spring Configuration Server

HTTP API Sources: git, Vault ** Git source repo: properties ** Alternative

• bash scripts to push config/state from repo to a database
• cron pulling config/state from database

Distribution

• JAR: Just classes
• Fat JAR: Main classes + static deps + meta
• WAR: Fat JAR + static content (outdated)

Docker

Java needs to be configured to run in containers to properly utilize memory

JVM Options

• -Xms min heap
• -Xmx max heap (often equal to -Xms, at least 4-8 Gb) example -Xms4g -Xmx4g

Deployment

• build -> release -> run ** Build JAR
• pre-commit hooks
• gradle build
• mvn build ** Release Configuration
• docker build
• ... ** Build jar -jar my-app.jar