Allow build info properties to be excluded

Update Maven and Gradle plugins to allow build info properties to be
excluded.

Prior to this commit, the `BuildPropertiesWriter` would fail with an
NPE if the group, artifact, name or version properties were `null`.

This was specifically problematic with the Gradle plugin, since its
DSL allows `null` properties which would either be passed to the writer
or, in the case of `artifact`, converted into a string value of
"unspecified".

See gh-27412

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/main/java/org/springframework/boot/maven/BuildInfoMojo.java

@@ -41,6 +41,7 @@ import org.springframework.boot.loader.tools.BuildPropertiesWriter.ProjectDetail
  * {@link MavenProject}.
  *
  * @author Stephane Nicoll
+ * @author Vedran Pavic
  * @since 1.4.0
  */
 @Mojo(name = "build-info", defaultPhase = LifecyclePhase.GENERATE_RESOURCES, threadSafe = true)
@@ -55,18 +56,48 @@ public class BuildInfoMojo extends AbstractMojo {
 	@Parameter(defaultValue = "${session}", readonly = true, required = true)
 	private MavenSession session;
 
-	/**
-	 * The Maven project.
-	 */
-	@Parameter(defaultValue = "${project}", readonly = true, required = true)
-	private MavenProject project;
-
 	/**
 	 * The location of the generated {@code build-info.properties} file.
 	 */
 	@Parameter(defaultValue = "${project.build.outputDirectory}/META-INF/build-info.properties")
 	private File outputFile;
 
+	/**
+	 * The value used for the {@code build.group} property. Defaults to
+	 * {@code project.groupId}. To disable the {@code build.group} property entirely, use
+	 * {@code 'off'}.
+	 * @since 2.6.0
+	 */
+	@Parameter(defaultValue = "${project.groupId}")
+	private String group;
+
+	/**
+	 * The value used for the {@code build.artifact} property. Defaults to
+	 * {@code project.artifactId}. To disable the {@code build.artifact} property
+	 * entirely, use {@code 'off'}.
+	 * @since 2.6.0
+	 */
+	@Parameter(defaultValue = "${project.artifactId}")
+	private String artifact;
+
+	/**
+	 * The value used for the {@code build.version} property. Defaults to
+	 * {@code project.version}. To disable the {@code build.version} property entirely,
+	 * use {@code 'off'}.
+	 * @since 2.6.0
+	 */
+	@Parameter(defaultValue = "${project.version}")
+	private String version;
+
+	/**
+	 * The value used for the {@code build.name} property. Defaults to
+	 * {@code project.name}. To disable the {@code build.name} property entirely, use
+	 * {@code 'off'}.
+	 * @since 2.6.0
+	 */
+	@Parameter(defaultValue = "${project.name}")
+	private String name;
+
 	/**
 	 * The value used for the {@code build.time} property in a form suitable for
 	 * {@link Instant#parse(CharSequence)}. Defaults to
@@ -88,8 +119,8 @@ public class BuildInfoMojo extends AbstractMojo {
 	@Override
 	public void execute() throws MojoExecutionException, MojoFailureException {
 		try {
-			ProjectDetails details = new ProjectDetails(this.project.getGroupId(), this.project.getArtifactId(),
-					this.project.getVersion(), this.project.getName(), getBuildTime(), this.additionalProperties);
+			ProjectDetails details = new ProjectDetails(getGroup(), getArtifact(), getVersion(), getName(),
+					getBuildTime(), this.additionalProperties);
 			new BuildPropertiesWriter(this.outputFile).writeBuildProperties(details);
 			this.buildContext.refresh(this.outputFile);
 		}
@@ -101,6 +132,34 @@ public class BuildInfoMojo extends AbstractMojo {
 		}
 	}
 
+	private String getGroup() {
+		if ("off".equalsIgnoreCase(this.group)) {
+			return null;
+		}
+		return this.group;
+	}
+
+	private String getArtifact() {
+		if ("off".equalsIgnoreCase(this.artifact)) {
+			return null;
+		}
+		return this.artifact;
+	}
+
+	private String getVersion() {
+		if ("off".equalsIgnoreCase(this.version)) {
+			return null;
+		}
+		return this.version;
+	}
+
+	private String getName() {
+		if ("off".equalsIgnoreCase(this.name)) {
+			return null;
+		}
+		return this.name;
+	}
+
 	private Instant getBuildTime() {
 		if (this.time == null || this.time.isEmpty()) {
 			Date startTime = this.session.getRequest().getStartTime();