Problem building gcloud project : COPY failed: no source files were specified

I have a java project with a DockerFile that looks like that:

FROM openjdk:8-jdk-alpine
RUN addgroup -S spring && adduser -S spring -G spring
USER spring:spring
ARG JAR_FILE=target/*.jar
COPY ${JAR_FILE} shape-shop-backend.jar
ENTRYPOINT ["java","-jar","/shape-shop-backend.jar"]

If I run docker like this :

C:devshape-shop>docker build -t testtest:1.0

It builds an image perfectly.

I am under the assumption that "gcloud builds submit" works in the same way. I have a project on the google cloud called whataboutanewproject, so in the same directory I run this command :

C:devshape-shop>gcloud builds submit --tag

But I get this error :

Digest: sha256:94792824df2df33402f201713f932b58cb9de94a0cd524164a0f2283343547b3
Status: Downloaded newer image for openjdk:8-jdk-alpine
 ---> a3562aa0b991
Step 2/6 : RUN addgroup -S spring && adduser -S spring -G spring
 ---> Running in 36cf2156a797
Removing intermediate container 36cf2156a797
 ---> 7320b32f6fe1
Step 3/6 : USER spring:spring
 ---> Running in f439aa9ca30e
Removing intermediate container f439aa9ca30e
 ---> 67f952c7bc2a
Step 4/6 : ARG JAR_FILE=target/*.jar
 ---> Running in 0bcfbf5f3b79
Removing intermediate container 0bcfbf5f3b79
 ---> 7519fa3bdc2f
Step 5/6 : COPY ${JAR_FILE} shape-shop-backend.jar
COPY failed: no source files were specified
ERROR: build step 0 "" failed: step exited with non-zero status: 1

ERROR: (gcloud.builds.submit) build d3704337-88de-4dda-a120-ebd2a01ee8c9 completed with status "FAILURE"


Why can it not process the DockerFile properly?

Does "gcloud build submit" even build an image? The documentation on the website is such utter garbage, that I have no clue actually what this "gcloud build submit" command even does.

Source: Docker Questions