Fix DockerTask.getBaseImage() and add Java 9 base image

[franzbecker]

The DockerTask.getBaseImage() method is currently not implemented correctly.

I had the following setup:

sourceCompatibility = JavaVersion.VERSION_1_9
targetCompatibility = JavaVersion.VERSION_1_9

docker {
    baseImage = "openjdk:9-jre"
}

and it still failed with:

Caused by: java.lang.IllegalArgumentException: No Java base image for the supplied target 1.9 found.
        at se.transmode.gradle.plugins.docker.JavaBaseImage.imageFor(JavaBaseImage.java:42)
        at se.transmode.gradle.plugins.docker.JavaBaseImage$imageFor.call(Unknown Source)
        at se.transmode.gradle.plugins.docker.DockerTask.determineBaseImage(DockerTask.groovy:81)

This is due to the fact that the base image for the specified Java version is still retrieved (and fails). In this case there is no need to retrieve it as an explicit base image is specified.

[codecov-io]

Codecov Report

Merging #135 into master will increase coverage by 0.93%. The diff coverage is 100%.

@@             Coverage Diff             @@
##             master    #135      +/-   ##
===========================================
+ Coverage     58.16%   59.1%   +0.93%     
  Complexity       82      82              
===========================================
  Files             9       9              
  Lines           306     313       +7     
  Branches         24      25       +1     
===========================================
+ Hits            178     185       +7     
  Misses          116     116              
  Partials         12      12

Impacted Files	Coverage Δ	Complexity Δ
.../transmode/gradle/plugins/docker/DockerTask.groovy	70.45% <100%> (+4.66%)	15 <4> (ø)	:arrow_down:
...transmode/gradle/plugins/docker/JavaBaseImage.java	76.92% <100%> (+1.92%)	3 <0> (ø)	:arrow_down:

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[bjornmagnusson]

Thanks for the contribution, looks good to me.

[gunkelolaf]

even though this pullrequest is merged, no new version was released @bjornmagnusson could you please release a new version?

[philbrock]

For anyone stuck with this issue and awaiting a new release, the workaround is to supply a partial Dockerfile that just defines whatever baseImage you're after.

e.g. in your docker task definition: dockerfile='docker/Dockerfile'

And the contents of that docker/Dockerfile: FROM openjdk:11-jre