Enable checkstyle

This commit updates the Gradle build to run checkstyle against the main
sources. Checks for tests, as well as certain rules, are disabled as a
first step.

See gh-1479

gradle/plugins/conventions-plugin/src/main/java/org/springframework/ws/gradle/conventions/CheckstyleConventions.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2005-2025 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.ws.gradle.conventions;
+
+import io.spring.javaformat.gradle.SpringJavaFormatPlugin;
+import org.gradle.api.Plugin;
+import org.gradle.api.Project;
+import org.gradle.api.artifacts.DependencySet;
+import org.gradle.api.plugins.JavaPlugin;
+import org.gradle.api.plugins.quality.Checkstyle;
+import org.gradle.api.plugins.quality.CheckstyleExtension;
+import org.gradle.api.plugins.quality.CheckstylePlugin;
+
+/**
+ * {@link Plugin} that applies conventions for checkstyle.
+ *
+ * @author Brian Clozel
+ * @author Stephane Nicoll
+ */
+public class CheckstyleConventions {
+
+	/**
+	 * Applies the Spring Java Format and Checkstyle plugins with the project conventions.
+	 * @param project the current project
+	 */
+	public void apply(Project project) {
+		project.getPlugins().withType(JavaPlugin.class, (java) -> {
+			project.getPlugins().apply(CheckstylePlugin.class);
+			project.getTasks().withType(Checkstyle.class).forEach(checkstyle -> checkstyle.getMaxHeapSize().set("1g"));
+			project.getTasks().named("checkstyleTest").configure(task -> task.setEnabled(false));
+			CheckstyleExtension checkstyle = project.getExtensions().getByType(CheckstyleExtension.class);
+			checkstyle.setToolVersion("10.21.1");
+			checkstyle.getConfigDirectory().set(project.getRootProject().file("src/checkstyle"));
+			String version = SpringJavaFormatPlugin.class.getPackage().getImplementationVersion();
+			DependencySet checkstyleDependencies = project.getConfigurations()
+				.getByName("checkstyle")
+				.getDependencies();
+			checkstyleDependencies.add(
+					project.getDependencies().create("com.puppycrawl.tools:checkstyle:" + checkstyle.getToolVersion()));
+			checkstyleDependencies
+				.add(project.getDependencies().create("io.spring.javaformat:spring-javaformat-checkstyle:" + version));
+		});
+	}
+
+}

gradle/plugins/conventions-plugin/src/main/java/org/springframework/ws/gradle/conventions/ConventionsPlugin.java

@@ -33,9 +33,10 @@ public class ConventionsPlugin implements Plugin<Project> {
 	@Override
 	public void apply(Project project) {
 		project.setGroup("org.springframework.ws");
-		project.getPlugins()
-			.withType(JavaBasePlugin.class)
-			.all((plugin) -> new JavaBasePluginConventions().apply(project));
+		project.getPlugins().withType(JavaBasePlugin.class).all((plugin) -> {
+			new JavaBasePluginConventions().apply(project);
+			new CheckstyleConventions().apply(project);
+		});
 		project.getPlugins().withType(JavaPlugin.class).all((plugin) -> new JavaPluginConventions().apply(project));
 		project.getPlugins()
 			.withType(MavenPublishPlugin.class)

src/checkstyle/checkstyle-suppressions.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0"?>
+<!DOCTYPE suppressions PUBLIC
+		"-//Checkstyle//DTD SuppressionFilter Configuration 1.2//EN"
+		"https://checkstyle.org/dtds/suppressions_1_2.dtd">
+<suppressions>
+	<suppress files="." checks="JavadocMethod"/>
+	<suppress files="." checks="SpringLambdaCheck"/>
+	<suppress files="." checks="SpringMethodVisibility"/>
+</suppressions>

src/checkstyle/checkstyle.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0"?>
+<!DOCTYPE module PUBLIC "-//Puppy Crawl//DTD Check Configuration 1.3//EN"
+		"https://checkstyle.org/dtds/configuration_1_3.dtd">
+<module name="com.puppycrawl.tools.checkstyle.Checker">
+	<module name="SuppressionFilter">
+		<property name="file" value="${config_loc}/checkstyle-suppressions.xml"/>
+	</module>
+	<module name="io.spring.javaformat.checkstyle.SpringChecks"/>
+</module>