Spring Boot Container with JLink
Here's how I computed the modules for jlink:
$ CP=`java -jar target/sample-docker-microservice-1.0-SNAPSHOT.jar --thin.classpath`
$ MODS=`jdeps --ignore-missing-deps --multi-release 17 --print-module-deps --class-path ${CP} target/classes/pl/piomin/microservices/person/Application.class`
Then you can create a jlink binary distro like this:
$ jlink --compress=2 --module-path ${JAVA_HOME}/jmods --add-modules "${MODS}" --no-header-files --no-man-pages --output target/thin
Run the app:
$ ./target/thin/bin/java -cp ${CP} pl.piomin.microservices.person.Application
The Dockerfile in the root of the project does the last bit for you and takes a step further by also setting up App CDS.
The docker image is about 160MB:
Cmp Size Command
5.6 MB FROM 695e5153d90d6a4
65 MB COPY /springboot-runtime /opt/jdk # buildkit
31 MB COPY /opt/app/repository /opt/app/repository # buildkit
13 kB COPY /opt/app/app.jar /opt/app # buildkit
691 kB COPY /opt/app/app.classlist /opt/app # buildkit
4.1 kB COPY /opt/app/classpath /opt/app # buildkit
69 MB RUN /bin/sh -c java -Xshare:dump -XX:SharedClassListFile=/opt/app...
The biggest chunks in there are:
- Java runtime, 65MB
- Jar files, 31MB (could probably be slimmed down)
- CDS cache, 69MB
(Original idea by @piomin.)
Modules Used
The MODS generated above from jdeps looks like quite a long list:
java.base,java.desktop,java.instrument,java.management,java.naming,java.prefs,java.rmi,java.scripting,java.sql,jdk.httpserver,jdk.jfr,jdk.unsupported
Spring 6 will get rid of java.desktop (the Java Beans dependency). You can slim that down to
java.base,java.desktop
and get an app to run with warnings (because java.management is missing).
Older Notes
Before Spring Boot 2.7 without java.naming you get errors in Spring:
Caused by: java.lang.NoClassDefFoundError: javax/naming/NamingException
at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.<init>(CommonAnnotationBeanPostProcessor.java:177) ~[spring-context-5.3.10.jar:5.3.10]
The pom.xml excludes snakeyaml. If you don't do that you also need java.logging.
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