Allow to customize how EntityScanner scans entities

This commit adds a protected method that lets an override customize the
configuration of the ClassPathScanningCandidateComponentProvider used
to scan entities.

Closes gh-23154

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/domain/EntityScanner.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -63,9 +63,8 @@ public class EntityScanner {
 		if (packages.isEmpty()) {
 			return Collections.emptySet();
 		}
-		ClassPathScanningCandidateComponentProvider scanner = new ClassPathScanningCandidateComponentProvider(false);
-		scanner.setEnvironment(this.context.getEnvironment());
-		scanner.setResourceLoader(this.context);
+		ClassPathScanningCandidateComponentProvider scanner = createClassPathScanningCandidateComponentProvider(
+				this.context);
 		for (Class<? extends Annotation> annotationType : annotationTypes) {
 			scanner.addIncludeFilter(new AnnotationTypeFilter(annotationType));
 		}
@@ -80,6 +79,22 @@ public class EntityScanner {
 		return entitySet;
 	}
 
+	/**
+	 * Create a {@link ClassPathScanningCandidateComponentProvider} to scan entities based
+	 * on the specified {@link ApplicationContext}.
+	 * @param context the {@link ApplicationContext} to use
+	 * @return a {@link ClassPathScanningCandidateComponentProvider} suitable to scan
+	 * entities
+	 * @since 2.4.0
+	 */
+	protected ClassPathScanningCandidateComponentProvider createClassPathScanningCandidateComponentProvider(
+			ApplicationContext context) {
+		ClassPathScanningCandidateComponentProvider scanner = new ClassPathScanningCandidateComponentProvider(false);
+		scanner.setEnvironment(context.getEnvironment());
+		scanner.setResourceLoader(context);
+		return scanner;
+	}
+
 	private List<String> getPackages() {
 		List<String> packages = EntityScanPackages.get(this.context).getPackageNames();
 		if (packages.isEmpty() && AutoConfigurationPackages.has(this.context)) {

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/domain/EntityScannerTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -16,12 +16,14 @@
 
 package org.springframework.boot.autoconfigure.domain;
 
+import java.util.Collections;
 import java.util.Set;
 
 import javax.persistence.Embeddable;
 import javax.persistence.Entity;
 
 import org.junit.jupiter.api.Test;
+import org.mockito.ArgumentCaptor;
 
 import org.springframework.boot.autoconfigure.domain.scan.a.EmbeddableA;
 import org.springframework.boot.autoconfigure.domain.scan.a.EntityA;
@@ -29,11 +31,18 @@ import org.springframework.boot.autoconfigure.domain.scan.b.EmbeddableB;
 import org.springframework.boot.autoconfigure.domain.scan.b.EntityB;
 import org.springframework.boot.autoconfigure.domain.scan.c.EmbeddableC;
 import org.springframework.boot.autoconfigure.domain.scan.c.EntityC;
+import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.core.type.filter.AnnotationTypeFilter;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+import static org.mockito.BDDMockito.given;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
 
 /**
  * Tests for {@link EntityScanner}.
@@ -79,6 +88,41 @@ class EntityScannerTests {
 		context.close();
 	}
 
+	@Test
+	void scanShouldUseCustomCandidateComponentProvider() throws ClassNotFoundException {
+		ClassPathScanningCandidateComponentProvider candidateComponentProvider = mock(
+				ClassPathScanningCandidateComponentProvider.class);
+		given(candidateComponentProvider.findCandidateComponents("org.springframework.boot.autoconfigure.domain.scan"))
+				.willReturn(Collections.emptySet());
+		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(ScanConfig.class);
+		TestEntityScanner scanner = new TestEntityScanner(context, candidateComponentProvider);
+		scanner.scan(Entity.class);
+		ArgumentCaptor<AnnotationTypeFilter> annotationTypeFilter = ArgumentCaptor.forClass(AnnotationTypeFilter.class);
+		verify(candidateComponentProvider).addIncludeFilter(annotationTypeFilter.capture());
+		verify(candidateComponentProvider)
+				.findCandidateComponents("org.springframework.boot.autoconfigure.domain.scan");
+		verifyNoMoreInteractions(candidateComponentProvider);
+		assertThat(annotationTypeFilter.getValue().getAnnotationType()).isEqualTo(Entity.class);
+	}
+
+	private static class TestEntityScanner extends EntityScanner {
+
+		private final ClassPathScanningCandidateComponentProvider candidateComponentProvider;
+
+		TestEntityScanner(ApplicationContext context,
+				ClassPathScanningCandidateComponentProvider candidateComponentProvider) {
+			super(context);
+			this.candidateComponentProvider = candidateComponentProvider;
+		}
+
+		@Override
+		protected ClassPathScanningCandidateComponentProvider createClassPathScanningCandidateComponentProvider(
+				ApplicationContext context) {
+			return this.candidateComponentProvider;
+		}
+
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	@EntityScan("org.springframework.boot.autoconfigure.domain.scan")
 	static class ScanConfig {