Of the three Docker image build methods we covered, Multi-stage builds are the way to go. This should be expected since the normal build included our application code, all of its dependencies, and our build tooling, and our multi-stage build contained only what we needed. You should see something like the following: Docker image size comparisonĪs you can see, the multi-stage build resulted in our smallest image, whereas the normal build resulted in our largest image. Modify your Dockerfile to contain the following: Every FROM statement creates a new base layer, and discards everything we don’t need from the previous FROM stage. With multi-stage Docker builds, we use multiple FROM statements for each build stage.
Results in the largest Docker image of our 3 methods.Integrates well with services that automatically “just build” using the present Dockerfile Docker controls the build process, therefore this method does not require the build tool or the JDK to be installed on the host machine beforehand.Stop the container once you are finished testing. $ docker run - d - p 8080 : 8080 anna/ docker- normal- build- demo : 1.0- SNAPSHOTĪgain, to test your container, navigate to localhost:8080. In the parent folder of your Spring Boot application, create a Dockerfile. Unzip the Spring Initializr project you generated as part of the prerequisites. In a package-only build, we will let Maven (or your build tool of choice) control the build process.
MAKE JAVA JAR FILE GENERATOR
You have a simple Spring Boot application (I used the Spring Initializr project generator with a Spring Web dependency).
MAKE JAVA JAR FILE FREE
If you want to follow along feel free to clone my repository at. In this post, I will review 3 different ways to create Docker images for Java applications.
MAKE JAVA JAR FILE UPGRADE
This is where Docker comes in! If you wish to upgrade a service, rather than redeploying your jar/war/ear to a new instance of an application server, you can just build a new Docker image with the upgraded deployment unit.
Instead of one giant, monolithic application, you build your application such that each service can run on its own. As you likely know by now, it is best practice to work in micro-services, deploying a small number of deployment units per JVM. Hopefully, at this point you have a picture like I have below in your folder.Long before Dockerfiles, Java developers worked with single deployment units (WARs, JARs, EARs, etc.). No problem, instead of the last line up above, type: C:\> C:\Path\to\jdk\bin\jar cvfm jarDemoCompiled.jar manifest.txt *.class Remember the path to jdk\bin\jar will be similar on your computer but almost definitely not exactly the same as mine. Here's the actual screen shot from my command prompt. When I don't usde the shortcut on my computer, I must type:Ĭ:\> C:\"Program Files"\Java\jdk1.6.0_02\bin\jar cvfm jarDemoCompiled.jar manifest.txt JarDemo.classĬvfm means "create a jar show verbose output specify the output jar file name ( jarDemoCompiled.jar) specify the manifest file name( manifest.txt) and use the file JarDemo.class to create the jar You can set the path as followsĬ:\> jar cvfm jarDemoCompiled.jar manifest.txt JarDemo.class
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