Fix "String.startsWith(String)" NPE when refreshing in eclipse

Fix NPE triggered by `PropertiesPersistableConfigurationObject` having
no `getDefaultResourceName()`.

See gh-48929

buildSrc/src/main/java/org/springframework/boot/build/EclipseConventions.java

@@ -40,22 +40,22 @@ class EclipseConventions {
 
 	void apply(Project project) {
 		project.getPlugins().withType(EclipsePlugin.class, (eclipse) -> configure(project, eclipse));
+		project.afterEvaluate(this::setJavaRuntimeName);
 	}
 
 	private DomainObjectCollection<JavaBasePlugin> configure(Project project, EclipsePlugin eclipsePlugin) {
-		TaskProvider<EclipseSynchronizeJdtSettings> eclipseSynchronizeJdtSettings = registerEclipseSynchronizeJdtSettingsTask(
-				project);
+		TaskProvider<?> synchronizeJdtSettings = registerEclipseSynchronizeJdtSettings(project);
 		return project.getPlugins().withType(JavaBasePlugin.class, (javaBase) -> {
 			EclipseModel model = project.getExtensions().getByType(EclipseModel.class);
-			model.synchronizationTasks(eclipseSynchronizeJdtSettings);
+			model.synchronizationTasks(synchronizeJdtSettings);
 			model.jdt(this::configureJdt);
 			model.classpath(this::configureClasspath);
 		});
 	}
 
-	private TaskProvider<EclipseSynchronizeJdtSettings> registerEclipseSynchronizeJdtSettingsTask(Project project) {
+	private TaskProvider<EclipseSynchronizeJdtSettings> registerEclipseSynchronizeJdtSettings(Project project) {
 		TaskProvider<EclipseSynchronizeJdtSettings> taskProvider = project.getTasks()
-			.register("eclipseSynchronizateJdt", EclipseSynchronizeJdtSettings.class);
+			.register("eclipseSynchronizeJdtSettings", EclipseSynchronizeJdtSettings.class);
 		taskProvider.configure((task) -> {
 			task.setDescription("Synchronizate the Eclipse JDT settings file from Buildship.");
 			task.setOutputFile(project.file(".settings/org.eclipse.jdt.core.prefs"));
@@ -82,6 +82,14 @@ class EclipseConventions {
 		});
 	}
 
+	private void setJavaRuntimeName(Project project) {
+		EclipseModel model = project.getExtensions().findByType(EclipseModel.class);
+		EclipseJdt jdt = (model != null) ? model.getJdt() : null;
+		if (jdt != null) {
+			model.getJdt().setJavaRuntimeName("JavaSE-" + JavaConventions.RUNTIME_JAVA_VERSION);
+		}
+	}
+
 	private boolean isKotlinPluginContributedBuildDirectory(ClasspathEntry entry) {
 		return (entry instanceof Library library) && isKotlinPluginContributedBuildDirectory(library.getPath())
 				&& isTest(library);

buildSrc/src/main/java/org/springframework/boot/build/EclipseSynchronizeJdtSettings.java

@@ -21,7 +21,6 @@ import java.util.Properties;
 import org.gradle.api.Task;
 import org.gradle.api.internal.PropertiesTransformer;
 import org.gradle.plugins.ide.api.PropertiesGeneratorTask;
-import org.gradle.plugins.ide.internal.generator.PropertiesPersistableConfigurationObject;
 
 import org.springframework.boot.build.EclipseSynchronizeJdtSettings.Configuration;
 
@@ -41,21 +40,12 @@ public abstract class EclipseSynchronizeJdtSettings extends PropertiesGeneratorT
 	protected void configure(Configuration configuration) {
 	}
 
-	static class Configuration extends PropertiesPersistableConfigurationObject {
+	static class Configuration extends EmptyPropertiesPersistableConfigurationObject {
 
 		Configuration(PropertiesTransformer transformer) {
 			super(transformer);
 		}
 
-		@Override
-		protected String getDefaultResourceName() {
-			return null;
-		}
-
-		@Override
-		protected void load(Properties properties) {
-		}
-
 		@Override
 		protected void store(Properties properties) {
 			properties.put("org.eclipse.jdt.core.compiler.release", "true");

buildSrc/src/main/java/org/springframework/boot/build/EmptyPropertiesPersistableConfigurationObject.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright 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.boot.build;
+
+import java.io.ByteArrayInputStream;
+import java.util.Properties;
+
+import org.gradle.api.internal.PropertiesTransformer;
+import org.gradle.internal.UncheckedException;
+import org.gradle.plugins.ide.internal.generator.PropertiesPersistableConfigurationObject;
+
+/**
+ * Base class for {@link PropertiesPersistableConfigurationObject} instances start empty
+ * and have no default resource.
+ *
+ * @author Phillip Webb
+ */
+abstract class EmptyPropertiesPersistableConfigurationObject extends PropertiesPersistableConfigurationObject {
+
+	EmptyPropertiesPersistableConfigurationObject(PropertiesTransformer transformer) {
+		super(transformer);
+	}
+
+	@Override
+	protected String getDefaultResourceName() {
+		return null;
+	}
+
+	@Override
+	public void loadDefaults() {
+		try {
+			load(new ByteArrayInputStream(new byte[0]));
+		}
+		catch (Exception ex) {
+			throw UncheckedException.throwAsUncheckedException(ex);
+		}
+	}
+
+	@Override
+	protected void load(Properties properties) {
+	}
+
+}