[FIXED] Enable load time weaving for Spring Boot app running in Docker

Issue

This seems like a simple thing that should have been done before, but I can't find anything. I have a Spring app (built with Maven, though I'd also like to know how to do this with Gradle) that gets run in a simple docker container:

FROM openjdk:11

COPY target/*-spring-boot.jar app.jar

CMD java -jar /app.jar

What do I need to do to enable load-time weaving with this setup?

Solution

I added spring-instrument to the pom

    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-instrument</artifactId>
    </dependency>

Added @EnableLoadTimeWeaving to the application class, changed my build script to unpack the jar

mkdir target/dependency
(cd target/dependency; jar -xf ../*-spring-boot.jar)
docker build -t myorg/myapp .

and updated the Dockerfile as per https://spring.io/guides/topicals/spring-boot-docker/

FROM openjdk:11

ARG DEPENDENCY=target/dependency
COPY ${DEPENDENCY}/BOOT-INF/lib /app/lib
COPY ${DEPENDENCY}/META-INF /app/META-INF
COPY ${DEPENDENCY}/BOOT-INF/classes /app

CMD java -cp app:app/lib/* -javaagent:"$(echo /app/lib/spring-instrument-*.jar)" com.myorg.MyApp

Answered By - Buddy Gorven
Answer Checked By - Marilyn (JavaFixing Volunteer)