Remove support for locating imports using spring.factories

With this commit, loading `@AutoConfiguration`,
`@ImportAutoConfiguration`, and `@ManagementContextConfiguration`
classes is supported with `.imports` files only. Support for loading
these classes with `spring.factories` is removed.

Closes gh-29699

Author: scottfrederick

buildSrc/src/main/java/org/springframework/boot/build/autoconfigure/AutoConfigurationMetadata.java

@@ -23,15 +23,13 @@
 import java.io.FileWriter;
 import java.io.IOException;
 import java.io.InputStream;
-import java.io.InputStreamReader;
-import java.io.Reader;
-import java.util.ArrayList;
 import java.util.Collections;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Properties;
 import java.util.Set;
 import java.util.concurrent.Callable;
+import java.util.stream.Collectors;
 
 import org.gradle.api.DefaultTask;
 import org.gradle.api.Task;
@@ -43,13 +41,13 @@
 import org.springframework.asm.ClassReader;
 import org.springframework.asm.Opcodes;
 import org.springframework.core.CollectionFactory;
-import org.springframework.util.StringUtils;
 
 /**
  * A {@link Task} for generating metadata describing a project's auto-configuration
  * classes.
  *
  * @author Andy Wilkinson
+ * @author Scott Frederick
  */
 public class AutoConfigurationMetadata extends DefaultTask {
 
@@ -60,10 +58,6 @@ public class AutoConfigurationMetadata extends DefaultTask {
 	private File outputFile;
 
 	public AutoConfigurationMetadata() {
-		getInputs()
-				.file((Callable<File>) () -> new File(this.sourceSet.getOutput().getResourcesDir(),
-						"META-INF/spring.factories"))
-				.withPathSensitivity(PathSensitivity.RELATIVE).withPropertyName("spring.factories");
 		getInputs()
 				.file((Callable<File>) () -> new File(this.sourceSet.getOutput().getResourcesDir(),
 						"META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports"))
@@ -99,9 +93,7 @@ void documentAutoConfiguration() throws IOException {
 
 	private Properties readAutoConfiguration() throws IOException {
 		Properties autoConfiguration = CollectionFactory.createSortedProperties(true);
-		Set<String> classNames = new LinkedHashSet<>();
-		classNames.addAll(readSpringFactories());
-		classNames.addAll(readAutoConfigurationsFile());
+		List<String> classNames = readAutoConfigurationsFile();
 		Set<String> publicClassNames = new LinkedHashSet<>();
 		for (String className : classNames) {
 			File classFile = findClassFile(className);
@@ -120,21 +112,6 @@ private Properties readAutoConfiguration() throws IOException {
 		return autoConfiguration;
 	}
 
-	/**
-	 * Reads auto-configurations from META-INF/spring.factories.
-	 * @return auto-configurations
-	 */
-	private Set<String> readSpringFactories() throws IOException {
-		File file = new File(this.sourceSet.getOutput().getResourcesDir(), "META-INF/spring.factories");
-		if (!file.exists()) {
-			return Collections.emptySet();
-		}
-		Properties springFactories = readSpringFactories(file);
-		String enableAutoConfiguration = springFactories
-				.getProperty("org.springframework.boot.autoconfigure.EnableAutoConfiguration");
-		return StringUtils.commaDelimitedListToSet(enableAutoConfiguration);
-	}
-
 	/**
 	 * Reads auto-configurations from
 	 * META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports.
@@ -146,29 +123,18 @@ private List<String> readAutoConfigurationsFile() throws IOException {
 		if (!file.exists()) {
 			return Collections.emptyList();
 		}
-		// Nearly identical copy of
-		// org.springframework.boot.context.annotation.ImportCandidates.load
-		try (BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(file)))) {
-			List<String> autoConfigurations = new ArrayList<>();
-			String line;
-			while ((line = reader.readLine()) != null) {
-				line = stripComment(line);
-				line = line.trim();
-				if (line.isEmpty()) {
-					continue;
-				}
-				autoConfigurations.add(line);
-			}
-			return autoConfigurations;
+		try (BufferedReader reader = new BufferedReader(new FileReader(file))) {
+			return reader.lines().map(this::stripComment).filter((line) -> !line.isEmpty())
+					.collect(Collectors.toList());
 		}
 	}
 
 	private String stripComment(String line) {
 		int commentStart = line.indexOf(COMMENT_START);
 		if (commentStart == -1) {
-			return line;
+			return line.trim();
 		}
-		return line.substring(0, commentStart);
+		return line.substring(0, commentStart).trim();
 	}
 
 	private File findClassFile(String className) {
@@ -182,12 +148,4 @@ private File findClassFile(String className) {
 		return null;
 	}
 
-	private Properties readSpringFactories(File file) throws IOException {
-		Properties springFactories = new Properties();
-		try (Reader in = new FileReader(file)) {
-			springFactories.load(in);
-		}
-		return springFactories;
-	}
-
 }

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/web/server/ManagementContextConfigurationImportSelector.java

@@ -29,7 +29,6 @@
 import org.springframework.core.OrderComparator;
 import org.springframework.core.Ordered;
 import org.springframework.core.annotation.Order;
-import org.springframework.core.io.support.SpringFactoriesLoader;
 import org.springframework.core.type.AnnotationMetadata;
 import org.springframework.core.type.classreading.MetadataReader;
 import org.springframework.core.type.classreading.SimpleMetadataReaderFactory;
@@ -44,6 +43,7 @@
  * @author Phillip Webb
  * @author Andy Wilkinson
  * @author Moritz Halbritter
+ * @author Scott Frederick
  * @see ManagementContextConfiguration
  * @see ImportCandidates
  */
@@ -90,11 +90,7 @@ private void addConfiguration(SimpleMetadataReaderFactory readerFactory,
 	}
 
 	protected List<String> loadFactoryNames() {
-		@SuppressWarnings("deprecation")
-		List<String> factoryNames = new ArrayList<>(
-				SpringFactoriesLoader.loadFactoryNames(ManagementContextConfiguration.class, this.classLoader));
-		ImportCandidates.load(ManagementContextConfiguration.class, this.classLoader).forEach(factoryNames::add);
-		return factoryNames;
+		return ImportCandidates.load(ManagementContextConfiguration.class, this.classLoader).getCandidates();
 	}
 
 	@Override

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

@@ -30,16 +30,13 @@
 import org.springframework.context.annotation.Conditional;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.annotation.AliasFor;
-import org.springframework.core.io.support.SpringFactoriesLoader;
 
 /**
  * Indicates that a class provides configuration that can be automatically applied by
  * Spring Boot. Auto-configuration classes are regular
  * {@link Configuration @Configuration} with the exception that
  * {@literal Configuration#proxyBeanMethods() proxyBeanMethods} is always {@code false}.
- * <p>
- * They are located using {@link ImportCandidates} and the {@link SpringFactoriesLoader}
- * mechanism (keyed against {@link EnableAutoConfiguration}).
+ * They are located using {@link ImportCandidates}.
  * <p>
  * Generally auto-configuration classes are marked as {@link Conditional @Conditional}
  * (most often using {@link ConditionalOnClass @ConditionalOnClass} and

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

@@ -17,13 +17,11 @@
 package org.springframework.boot.autoconfigure;
 
 import java.io.IOException;
-import java.util.ArrayList;
 import java.util.List;
 
 import org.springframework.beans.factory.BeanClassLoaderAware;
 import org.springframework.boot.context.annotation.ImportCandidates;
 import org.springframework.context.annotation.Configuration;
-import org.springframework.core.io.support.SpringFactoriesLoader;
 import org.springframework.core.type.classreading.MetadataReader;
 import org.springframework.core.type.classreading.MetadataReaderFactory;
 import org.springframework.core.type.filter.TypeFilter;
@@ -32,6 +30,7 @@
  * A {@link TypeFilter} implementation that matches registered auto-configuration classes.
  *
  * @author Stephane Nicoll
+ * @author Scott Frederick
  * @since 1.5.0
  */
 public class AutoConfigurationExcludeFilter implements TypeFilter, BeanClassLoaderAware {
@@ -64,11 +63,8 @@ private boolean isAutoConfiguration(MetadataReader metadataReader) {
 
 	protected List<String> getAutoConfigurations() {
 		if (this.autoConfigurations == null) {
-			@SuppressWarnings("deprecation")
-			List<String> autoConfigurations = new ArrayList<>(
-					SpringFactoriesLoader.loadFactoryNames(EnableAutoConfiguration.class, this.beanClassLoader));
-			ImportCandidates.load(AutoConfiguration.class, this.beanClassLoader).forEach(autoConfigurations::add);
-			this.autoConfigurations = autoConfigurations;
+			this.autoConfigurations = ImportCandidates.load(AutoConfiguration.class, this.beanClassLoader)
+					.getCandidates();
 		}
 		return this.autoConfigurations;
 	}

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

@@ -69,6 +69,7 @@
  * @author Stephane Nicoll
  * @author Madhura Bhave
  * @author Moritz Halbritter
+ * @author Scott Frederick
  * @since 1.3.0
  * @see EnableAutoConfiguration
  */
@@ -168,36 +169,23 @@ protected Class<?> getAnnotationClass() {
 	}
 
 	/**
-	 * Return the auto-configuration class names that should be considered. By default
-	 * this method will load candidates using {@link ImportCandidates} with
-	 * {@link #getSpringFactoriesLoaderFactoryClass()}. For backward compatible reasons it
-	 * will also consider {@link SpringFactoriesLoader} with
-	 * {@link #getSpringFactoriesLoaderFactoryClass()}.
+	 * Return the auto-configuration class names that should be considered. By default,
+	 * this method will load candidates using {@link ImportCandidates}.
 	 * @param metadata the source metadata
 	 * @param attributes the {@link #getAttributes(AnnotationMetadata) annotation
 	 * attributes}
 	 * @return a list of candidate configurations
 	 */
 	protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) {
-		@SuppressWarnings("deprecation")
-		List<String> configurations = new ArrayList<>(
-				SpringFactoriesLoader.loadFactoryNames(getSpringFactoriesLoaderFactoryClass(), getBeanClassLoader()));
-		ImportCandidates.load(AutoConfiguration.class, getBeanClassLoader()).forEach(configurations::add);
+		List<String> configurations = ImportCandidates.load(AutoConfiguration.class, getBeanClassLoader())
+				.getCandidates();
 		Assert.notEmpty(configurations,
-				"No auto configuration classes found in META-INF/spring.factories nor in META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports. If you "
+				"No auto configuration classes found in "
+						+ "META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports. If you "
 						+ "are using a custom packaging, make sure that file is correct.");
 		return configurations;
 	}
 
-	/**
-	 * Return the class used by {@link SpringFactoriesLoader} to load configuration
-	 * candidates.
-	 * @return the factory class
-	 */
-	protected Class<?> getSpringFactoriesLoaderFactoryClass() {
-		return EnableAutoConfiguration.class;
-	}
-
 	private void checkExcludedClasses(List<String> configurations, Set<String> exclusions) {
 		List<String> invalidExcludes = new ArrayList<>(exclusions.size());
 		for (String exclusion : exclusions) {

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

@@ -32,7 +32,6 @@
 import org.springframework.context.annotation.Conditional;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
-import org.springframework.core.io.support.SpringFactoriesLoader;
 
 /**
  * Enable auto-configuration of the Spring Application Context, attempting to guess and
@@ -61,9 +60,8 @@
  * and classes can be searched.
  * <p>
  * Auto-configuration classes are regular Spring {@link Configuration @Configuration}
- * beans. They are located using {@link ImportCandidates} and the
- * {@link SpringFactoriesLoader} mechanism (keyed against this class). Generally
- * auto-configuration beans are {@link Conditional @Conditional} beans (most often using
+ * beans. They are located using {@link ImportCandidates}. Generally auto-configuration
+ * beans are {@link Conditional @Conditional} beans (most often using
  * {@link ConditionalOnClass @ConditionalOnClass} and
  * {@link ConditionalOnMissingBean @ConditionalOnMissingBean} annotations).
  *

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

@@ -32,7 +32,6 @@
 import org.springframework.core.annotation.AnnotatedElementUtils;
 import org.springframework.core.annotation.AnnotationAttributes;
 import org.springframework.core.annotation.AnnotationUtils;
-import org.springframework.core.io.support.SpringFactoriesLoader;
 import org.springframework.core.type.AnnotationMetadata;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.LinkedMultiValueMap;
@@ -46,6 +45,7 @@
  * @author Phillip Webb
  * @author Andy Wilkinson
  * @author Moritz Halbritter
+ * @author Scott Frederick
  */
 class ImportAutoConfigurationImportSelector extends AutoConfigurationImportSelector implements DeterminableImports {
 
@@ -96,11 +96,7 @@ private Collection<String> getConfigurationsForAnnotation(Class<?> source, Annot
 	}
 
 	protected Collection<String> loadFactoryNames(Class<?> source) {
-		@SuppressWarnings("deprecation")
-		List<String> factoryNames = new ArrayList<>(
-				SpringFactoriesLoader.loadFactoryNames(source, getBeanClassLoader()));
-		ImportCandidates.load(source, getBeanClassLoader()).forEach(factoryNames::add);
-		return factoryNames;
+		return ImportCandidates.load(source, getBeanClassLoader()).getCandidates();
 	}
 
 	@Override

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

@@ -213,10 +213,7 @@ private String[] selectImports(Class<?> source) {
 	}
 
 	private List<String> getAutoConfigurationClassNames() {
-		List<String> autoConfigurationClassNames = new ArrayList<>();
-		ImportCandidates.load(AutoConfiguration.class, getClass().getClassLoader())
-				.forEach(autoConfigurationClassNames::add);
-		return autoConfigurationClassNames;
+		return ImportCandidates.load(AutoConfiguration.class, getClass().getClassLoader()).getCandidates();
 	}
 
 	private class TestAutoConfigurationImportSelector extends AutoConfigurationImportSelector {

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/annotation/ImportCandidates.java

@@ -37,6 +37,7 @@
  * candidates.
  *
  * @author Moritz Halbritter
+ * @author Scott Frederick
  * @since 2.7.0
  */
 public final class ImportCandidates implements Iterable<String> {
@@ -57,6 +58,14 @@ public Iterator<String> iterator() {
 		return this.candidates.iterator();
 	}
 
+	/**
+	 * Returns the list of loaded import candidates.
+	 * @return the list of import candidates
+	 */
+	public List<String> getCandidates() {
+		return this.candidates;
+	}
+
 	/**
 	 * Loads the names of import candidates from the classpath.
 	 *