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Update reference documentation for layer changes

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Update the reference documentation following the jar format changes.

See gh-20813
This commit is contained in:
Madhura Bhave
2020-04-02 23:27:47 -07:00
committed by Phillip Webb
parent d61a79d90b
commit 0e1394ef30
2 changed files with 31 additions and 83 deletions
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29
spring-boot-project/spring-boot-docs/src/docs/asciidoc/deployment.adoc
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@@ -33,33 +33,10 @@ Once you have unpacked the jar file, you can also get an extra boost to startup
$ java -cp BOOT-INF/classes:BOOT-INF/lib/* com.example.MyApplication
----
More efficient container images can also be created by copying the dependencies to the image as a separate layer from the application classes and resources (which normally change more frequently).
There is more than one way to achieve this layer separation.
For example, using a `Dockerfile` you could express it in this form:
NOTE: Using the `JarLauncher` over the application's main method has the added benefit of a predictable classpath order.
The jar contains a `classpath.idx` file which is used by the `JarLauncher` when constructing the classpath.
[indent=0]
----
FROM openjdk:8-jdk-alpine AS builder
WORKDIR target/dependency
ARG APPJAR=target/*.jar
COPY ${APPJAR} app.jar
RUN jar -xf ./app.jar
FROM openjdk:8-jre-alpine
VOLUME /tmp
ARG DEPENDENCY=target/dependency
COPY --from=builder ${DEPENDENCY}/BOOT-INF/lib /app/lib
COPY --from=builder ${DEPENDENCY}/META-INF /app/META-INF
COPY --from=builder ${DEPENDENCY}/BOOT-INF/classes /app
ENTRYPOINT ["java","-cp","app:app/lib/*","com.example.MyApplication"]
----
Assuming the above `Dockerfile` is in the current directory, your docker image can be built with `docker build .`, or optionally specifying the path to your application jar, as shown in the following example:
[indent=0]
----
docker build --build-arg APPJAR=path/to/myapp.jar .
----
More efficient container images can also be created by <<spring-boot-features.adoc#building-docker-images,creating separate layers>> for your dependencies and application classes and resources (which normally change more frequently).