Merge pull request #26690 from jaminh

* pr/26690:
  Polish "Allow SpringApplicationBuilder to specify a ResourceLoader"
  Allow SpringApplicationBuilder to specify a ResourceLoader

Closes gh-26690

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

@@ -94,21 +94,40 @@ public class SpringApplicationBuilder {
 	private boolean configuredAsChild = false;
 
 	public SpringApplicationBuilder(Class<?>... sources) {
-		this.application = createSpringApplication(sources);
+		this(null, sources);
+	}
+
+	public SpringApplicationBuilder(ResourceLoader resourceLoader, Class<?>... sources) {
+		this.application = createSpringApplication(resourceLoader, 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}
+	 * 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 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 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 SpringApplication} instance
+	 * @since 2.6.0
+	 */
+	protected SpringApplication createSpringApplication(ResourceLoader resourceLoader, Class<?>... sources) {
+		return new SpringApplication(resourceLoader, sources);
+	}
+
 	/**
 	 * Accessor for the current application context.
 	 * @return the current application context (or null if not yet running)

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;
 
@@ -309,6 +312,22 @@ class SpringApplicationBuilderTests {
 		assertThat(builder.application().getEnvironmentPrefix()).isEqualTo("test");
 	}
 
+	@Test
+	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)
 	static class ExampleConfig {
 
@@ -319,6 +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());