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CS156

In a Maven pom.xml file, there is a <plugins> section, which, unsurprisingly, contains one or more <plugin> elements:

<plugins>
  <plugin>
  ...
  </plugin>
  
  
  <plugin>
  ...
  </plugin>

</plugins>

Plugins extend the functionality of Maven. Here are a few common ones that you may see in CS156, and what each of them does.

maven-compiler-plugin/

The main purpose of this is configure the compiler used to compile our Java code.

The most important thing we configure though this plugin is the version of Java that we’ll be using to compile our code.

For example, this sets the version to Java 17:

    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-compiler-plugin</artifactId>
      <version>3.8.0</version>
      <configuration>
        <release>17</release>
      </configuration>
    </plugin>

Learn More: <https://maven.apache.org/plugins/maven-compiler-plugin/

jacoco-maven-plugin

This plugin allows us to invoke the Jacoco (Java Code Coverage) tool to measure how well our JUnit tests are covering our code.

This version works with JUnit 5 and Java 17:

   <plugin>
      <groupId>org.jacoco</groupId>
      <artifactId>jacoco-maven-plugin</artifactId>
      <version>0.8.7</version>
      <executions>
          <execution>
              <goals>
                  <goal>prepare-agent</goal>
              </goals>
          </execution>
          <execution>
              <id>report</id>
              <phase>prepare-package</phase>
              <goals>
                  <goal>report</goal>
              </goals>
          </execution>
      </executions>
  </plugin>

maven-surefire-plugin

This plugin has to do with gathering information about runs of the test suites that are part of an application.

Our experience has been that when migrating a project to JUnit5, it is necessary to specify a version of this plugin that is at least higher than version 22.2.0, or the tests may not run.

Example:

            <!-- needed to get JUnit 5 tests to run -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <!-- JUnit 5 requires Surefire version 2.22.0 or higher -->
                <version>2.22.0</version>
            </plugin>

According to the documentation:

The Surefire Plugin is used during the test phase of the build lifecycle to execute the unit tests of an application. It generates reports in two different file formats:

  • Plain text files (*.txt)
  • XML files (*.xml)

By default, these files are generated in ${basedir}/target/surefire-reports/TEST-*.xml