Polish "Allow SpringApplicationBuilder to specify a ResourceLoader"

See gh-26690

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/builder/SpringApplicationBuilder.java

@@ -94,7 +94,7 @@ public class SpringApplicationBuilder {
 	private boolean configuredAsChild = false;
 
 	public SpringApplicationBuilder(Class<?>... sources) {
-		this.application = createSpringApplication(null, sources);
+		this(null, sources);
 	}
 
 	public SpringApplicationBuilder(ResourceLoader resourceLoader, Class<?>... sources) {
@@ -102,29 +102,27 @@ public class SpringApplicationBuilder {
 	}
 
 	/**
-	 * Creates a new {@link org.springframework.boot.SpringApplication} instances from the
-	 * given sources. Subclasses may override in order to provide a custom subclass of
-	 * {@link org.springframework.boot.SpringApplication}
+	 * Creates a new {@link SpringApplication} instance from the given sources. Subclasses
+	 * may override in order to provide a custom subclass of {@link SpringApplication}
 	 * @param sources the sources
-	 * @return the {@link org.springframework.boot.SpringApplication} instance
+	 * @return the {@link SpringApplication} instance
 	 * @since 1.1.0
-	 * @deprecated Use {@link #createSpringApplication(ResourceLoader, Class...)} with
-	 * null resource loader
+	 * @deprecated since 2.6.0 for removal in 2.8.0 in favor of
+	 * {@link #createSpringApplication(ResourceLoader, Class...)}
 	 */
+	@Deprecated
 	protected SpringApplication createSpringApplication(Class<?>... sources) {
 		return new SpringApplication(sources);
 	}
 
 	/**
-	 * Creates a new {@link org.springframework.boot.SpringApplication} instances from the
-	 * given sources. Subclasses may override in order to provide a custom subclass of
-	 * {@link org.springframework.boot.SpringApplication}
-	 * @param resourceLoader the resource loader, can be null to use default resource
-	 * loader (see
-	 * {@link org.springframework.boot.SpringApplication#SpringApplication(ResourceLoader, Class...)})
+	 * Creates a new {@link SpringApplication} instances from the given sources using the
+	 * given {@link ResourceLoader}. Subclasses may override in order to provide a custom
+	 * subclass of {@link SpringApplication}
+	 * @param resourceLoader the resource loader (can be null)
 	 * @param sources the sources
-	 * @return the {@link org.springframework.boot.SpringApplication} instance
-	 * @since 2.5.0
+	 * @return the {@link SpringApplication} instance
+	 * @since 2.6.0
 	 */
 	protected SpringApplication createSpringApplication(ResourceLoader resourceLoader, Class<?>... sources) {
 		return new SpringApplication(resourceLoader, sources);

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/builder/SpringApplicationBuilderTests.java

@@ -20,11 +20,13 @@ import java.net.URL;
 import java.net.URLClassLoader;
 import java.util.Collections;
 
+import org.assertj.core.api.InstanceOfAssertFactories;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.boot.ApplicationArguments;
 import org.springframework.boot.ApplicationContextFactory;
+import org.springframework.boot.SpringApplication;
 import org.springframework.boot.SpringApplicationShutdownHookInstance;
 import org.springframework.boot.WebApplicationType;
 import org.springframework.context.ApplicationContext;
@@ -41,6 +43,7 @@ import org.springframework.util.StringUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.verify;
 
@@ -310,13 +313,19 @@ class SpringApplicationBuilderTests {
 	}
 
 	@Test
-	void createWithResourceLoader() {
-		ClassLoader classLoader = new URLClassLoader(new URL[0], getClass().getClassLoader());
-		SpringApplicationBuilder application = new SpringApplicationBuilder(new DefaultResourceLoader(classLoader),
-				ExampleConfig.class)
-						.contextFactory(ApplicationContextFactory.ofContextClass(SpyApplicationContext.class));
-		this.context = application.run();
-		assertThat(this.context.getClassLoader()).isEqualTo(classLoader);
+	void customApplicationWithResourceLoader() {
+		ResourceLoader resourceLoader = mock(ResourceLoader.class);
+		SpringApplicationBuilder applicationBuilder = new SpringApplicationBuilder(resourceLoader,
+				ExampleConfig.class) {
+			@Override
+			protected SpringApplication createSpringApplication(ResourceLoader resourceLoader, Class<?>... sources) {
+				return new CustomSpringApplication(resourceLoader, sources);
+			}
+		};
+		SpringApplication application = applicationBuilder.build();
+		assertThat(application).isInstanceOf(CustomSpringApplication.class)
+				.asInstanceOf(InstanceOfAssertFactories.type(CustomSpringApplication.class))
+				.satisfies((customApp) -> assertThat(customApp.resourceLoader).isEqualTo(resourceLoader));
 	}
 
 	@Configuration(proxyBeanMethods = false)
@@ -329,6 +338,17 @@ class SpringApplicationBuilderTests {
 
 	}
 
+	static class CustomSpringApplication extends SpringApplication {
+
+		private final ResourceLoader resourceLoader;
+
+		CustomSpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
+			super(resourceLoader, primarySources);
+			this.resourceLoader = resourceLoader;
+		}
+
+	}
+
 	static class SpyApplicationContext extends AnnotationConfigApplicationContext {
 
 		private final ConfigurableApplicationContext applicationContext = spy(new AnnotationConfigApplicationContext());