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Base Project Maven

Speed and consistency of development is essential for a strong software company. A base project setup can provide that essential foundation for accelerating development efforts. It has

  • many common problems already solved,
  • many important choices already made,
  • many examples of plugins and configurations.

By cloning the base project and customizing it to your needs, you can get running in minutes and create consistency for months and years ahead.

Building and running the base project

  1. Install Git for your operating system: https://git-scm.com/download/.
  2. Install IntelliJ IDEA for your operating system: https://www.jetbrains.com/idea/download/.
  3. Install Docker engine for your operating system and start it: https://docs.docker.com/engine/install/.
  4. Start IntelliJ IDEA -> Get from Version Control -> GitHub -> https://github.com/romanastr/base-project-maven.git -> specify the directory -> Clone.
  5. Open Terminal Tool Window in IntelliJ: View -> Tool Windows -> Terminal.
  6. Login to docker with docker login command (works on any operating system).
  7. Switch to your own username on Docker Hub in JIB plugin configuration (see description of the plugin below) in demo/pom.xml file: <image>index.docker.io/YOUR_USERNAME/YOUR_PROJECT_NAME:YOUR_TAG</image>. Specify docker credentials helper for your operating system in parent pom.xml as <credHelper>YOUR_HELPER</credHelper>. Substitute YOUR_HELPER with desktop in Windows 10. Check that your chosen helper is available by running docker-credential-YOUR_HELPER list command, e.g. docker-credential-desktop list on Windows 10. The output should contain a line with your username.
  8. Compile the project from the command line, build the docker image, and push it to your Docker Hub by running mvnw.cmd clean install -P image-build in the Terminal (works on any operating system). The command does not require Maven installed - it downloads Maven from the Internet, if it is not found. Alternative, Maven Tool Window in IntelliJ provides very flexible interface for working with Maven.
  9. Run the produced docker image on your local machine: docker run -p 8080:8080 --rm --name maven YOUR_USERNAME/YOUR_PROJECT_NAME:YOUR_TAG. Alternatively, you can run a pre-compiled docker image from the base project: docker run -p 8080:8080 --rm --name maven romanastr/base-project-maven:1.0.
  10. Check that the Demo application is live by opening the health check URL in the browser: http://localhost:8080/actuator/health - you should see the following JSON response: {"status":"UP"}.

Now, once you get it working, let us discuss choices and decisions made in the project.

Maven

Two mainstream dependency management systems for Java applications in 2020 is Maven and Gradle. Gradle appears more versatile and flexible, thus suitable for large projects. Maven has more plugins available and more customization examples online. Maven has a wider community support. Thus, Maven is a tool of choice for small to medium size projects.

Java version

Long-term support (LTS) Java versions are preferred to new Java releases for applications in production due to the availability of security and functionality patches. Java 11 is the latest LTS version with Java 17 (LTS) being the next one. Two major implementations of Java platform is Oracle and OpenJDK community (which has a large number of Oracle engineers). Oracle implementations can be used with a monthly paid subscription, which allows running commercial software, while OpenJDK builds are free for all uses and substantially unrestricted. OpenJDK implementations appear well-supported and frequently updated. Thus, many companies prefer to use free OpenJDK versions of Java, which we adopt as well. We use the official OpenJDK images on DockerHub to build application docker containers.

Java frameworks

Spring Boot 2 is the most popular Java framework in 2020. The set of dependencies tested to work with Spring Boot is defined in spring-boot-dependencies project. Importing those dependencies from the pom dependency instead of making Spring Boot a parent provides the most flexibility to adjust the dependencies as well as choose a different parent project. The set includes the following test dependencies: JUnit 5 for testing and AssertJ for assertions. Lombok annotations reduce boilerplate code, but need to be coupled with an IDEA plugin to properly trace usage (e.g., Lombok plugin for IntelliJ IDEA). spring-boot-starter-web dependency provides embedded Tomcat to run a web server on, by default on port "8080". spring-boot-starter-actuator dependency provides production-ready features for application monitoring and management including a health check endpoint at "actuator/health" url path.

Maven plugins

The power of Maven in its plugins. The following plugins make the base project work:

  • maven-compiler-plugin facilitates compilation with Java compiler. It needs to be explicitly included to specify the Java version;
  • maven-surefire-plugin enables running unit tests;
  • maven-failsafe-plugin enables running integration tests. All test classes with names ending with IntegrationTest are considered integration tests, while all other test classes are classified as unit tests;
  • jacoco-maven-plugin enforces code coverage with unit tests. Classes with names ending with Application and Configuration are excluded from code coverage check and from the reports. 100% code line and branch coverage is enforced;
  • maven-checkstyle-plugin enforces code style. Strict verbose configuration is implemented to show warnings and fail on them. One of the predefined style definitions, google_checks.xml is utilized. The same style can be imported to IntelliJ IDEA from this IntelliJ style file
    After importing this style, IntelliJ can automatically refactor code in each file to adhere to the checkstyle. Note that Google style has indentation with 2 spaces instead of a default IntelliJ indentation with 4 spaces, which takes times to get used to, but it saves space;
  • spring-boot-maven-plugin facilitates building an executable uber Jar file containing all classes, resources, and dependencies;
  • maven-jib-plugin enables building Docker images without an explicit Dockerfile. Configuration of a JIB plugin includes the base docker image with Java. JIB issues a warning, if the base image is defined by a name and a tag, since a different image can be later uploaded with the same name:tag combination. It is recommended to define the starting image by its hash, which is what we did. Credentials helper is utilized to integrate with Docker engine and avoid storing passwords in plain text. Also, one has to change the DockerHub username in the target image name (see above). JIB plugin configuration is split between the parent pom.xml and the child pom.xml to define the uniform base starting image in the parent, but to define the target image name in the child modules individually. Any other Docker registry can be readily used as well.

Maven profiles

Several profiles are introduced to toggle plugin executions:

  • unit-tests profile enables executing unit tests and checking test coverage, when active. It is active by default / if no profiles are specified;
  • integration-tests profile enables running integration tests independently of unit tests;
  • image-build profile enables building Docker image and uploading it to DockerHub registry.

Types of tests and test coverage

The traditional test pyramid heavily relies on the foundations built with the unit tests. They are easy to execute and can readily test all special conditions. A smaller set of longer running integration tests allows checking functionality of the application for a subset of inputs. It is highly beneficial to have 100% code coverage with unit tests. The difference between 95% code coverage and 100% code coverage is huge - when forced to test everything, one would naturally simplify the code and eliminate impossible paths, while allowing for adequate defensive programming. This readily becomes a good habit. The integration tests might not need to have any specific code coverage target, but would rather test overall application functionality.

.gitignore

.gitignore file specifies to Git, which files should be ignored in status checks and never committed to source control. A sample file we adopted is crowdsourced in here.

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