Upgrade to spring-javaformat 0.0.31

Closes gh-29633

.springjavaformatconfig

@@ -0,0 +1 @@
+java-baseline=8

buildSrc/gradle.properties

@@ -1 +1 @@
-javaFormatVersion=0.0.29
+javaFormatVersion=0.0.31

buildSrc/src/main/java/org/springframework/boot/build/mavenplugin/MavenPluginPlugin.java

@@ -38,6 +38,9 @@ import javax.xml.xpath.XPathConstants;
 import javax.xml.xpath.XPathExpressionException;
 import javax.xml.xpath.XPathFactory;
 
+import io.spring.javaformat.config.IndentationStyle;
+import io.spring.javaformat.config.JavaBaseline;
+import io.spring.javaformat.config.JavaFormatConfig;
 import io.spring.javaformat.formatter.FileEdit;
 import io.spring.javaformat.formatter.FileFormatter;
 import org.gradle.api.DefaultTask;
@@ -98,6 +101,20 @@ import org.springframework.util.Assert;
  */
 public class MavenPluginPlugin implements Plugin<Project> {
 
+	private static final JavaFormatConfig FORMATTER_CONFIG = new JavaFormatConfig() {
+
+		@Override
+		public JavaBaseline getJavaBaseline() {
+			return JavaBaseline.V8;
+		}
+
+		@Override
+		public IndentationStyle getIndentationStyle() {
+			return IndentationStyle.TABS;
+		}
+
+	};
+
 	@Override
 	public void apply(Project project) {
 		project.getPlugins().apply(JavaLibraryPlugin.class);
@@ -297,7 +314,7 @@ public class MavenPluginPlugin implements Plugin<Project> {
 
 		@TaskAction
 		void syncAndFormat() {
-			FileFormatter formatter = new FileFormatter();
+			FileFormatter formatter = new FileFormatter(FORMATTER_CONFIG);
 			for (File output : this.generator.getOutputs().getFiles()) {
 				formatter.formatFiles(getProject().fileTree(output), StandardCharsets.UTF_8)
 						.forEach((edit) -> save(output, edit));