Merge pull request #1 from nais/jar-file-build-arg

Set JAR file as environment variable

Author: joakibj

java-8/Dockerfile

@@ -13,4 +13,4 @@ WORKDIR /app
 
 EXPOSE 8080
 
-CMD ["sh", "-c", "java", "$DEFAULT_JAVA_OPTS $JAVA_OPTS", "-jar", "/app/app.jar"]
+CMD ["sh", "-c", "java", "$DEFAULT_JAVA_OPTS", "$JAVA_OPTS", "-jar", "${JAR_FILE:-app.jar}"]

java-8/README.md

@@ -7,16 +7,40 @@ WIP draft.
 Usage
 ---------------------
 
-Build your app to `./target/app.jar`.
+Build your app to `./target/app.jar` or provide your own jar file 
+using the `JAR_FILE` environment variable.
 
 Make your app expose services on port 8080 as default.
 
 Include custom Java options in `$JAVA_OPTS`.
 
+Example
+---------------------
+
+The `Dockerfile` below allows us to specify an alternate JAR file build time (via `--build-arg JAR_FILE=my.jar`) 
+and run time as an environment variable. We also specify additional options for the JVM:
 
 ```
 FROM nais:java-8
 
-ENV JAVA_OPTS="-Djavax.net.ssl.trustStore=/truststore.jks -Djavax.net.ssl.trustStorePassword=changeit"
+ARG JAR_FILE
+ENV JAR_FILE ${JAR_FILE}
+
+ENV JAVA_OPTS="-Djavax.net.ssl.trustStore=/truststore.jks \
+               -Djavax.net.ssl.trustStorePassword=changeit"
+
+```
+
+The JAR file can be a bit simplified during build:
 
+```
+ARG BUILD_NO
+ENV JAR_FILE ${JAR_FILE:-myapp-${BUILD_NO}.jar}
+```
+
+This will either use the environment variable `JAR_FILE` or fall back 
+to the default `myapp-BUILD_NO`, where `BUILD_NO` is specified build time:
+
+```
+docker build -t myapp:latest --build-arg BUILD_NO=1337 .
 ```