Support binding with BeanFactory ConversionService

Update `BindConverter` so that multiple `ConverterServices` can be
specified when binding. This change allows `ConversionServiceDeducer`
to add both the `BeanFactory` conversion service as well as a
custom `ApplicationConversionService` when beans annotated with
`@ConfigurationPropertiesBinding` are found.

Fixes gh-26089

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/ConfigurationPropertiesBinder.java

@@ -166,7 +166,7 @@ class ConfigurationPropertiesBinder {
 	private Binder getBinder() {
 		if (this.binder == null) {
 			this.binder = new Binder(getConfigurationPropertySources(), getPropertySourcesPlaceholdersResolver(),
-					getConversionService(), getPropertyEditorInitializer(), null,
+					getConversionServices(), getPropertyEditorInitializer(), null,
 					ConfigurationPropertiesBindConstructorProvider.INSTANCE);
 		}
 		return this.binder;
@@ -180,8 +180,8 @@ class ConfigurationPropertiesBinder {
 		return new PropertySourcesPlaceholdersResolver(this.propertySources);
 	}
 
-	private ConversionService getConversionService() {
-		return new ConversionServiceDeducer(this.applicationContext).getConversionService();
+	private List<ConversionService> getConversionServices() {
+		return new ConversionServiceDeducer(this.applicationContext).getConversionServices();
 	}
 
 	private Consumer<PropertyEditorRegistry> getPropertyEditorInitializer() {

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/ConversionServiceDeducer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -20,10 +20,9 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 
-import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.ListableBeanFactory;
-import org.springframework.beans.factory.NoSuchBeanDefinitionException;
 import org.springframework.beans.factory.annotation.BeanFactoryAnnotationUtils;
+import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
 import org.springframework.boot.convert.ApplicationConversionService;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ConfigurableApplicationContext;
@@ -31,6 +30,7 @@ import org.springframework.core.convert.ConversionService;
 import org.springframework.core.convert.converter.Converter;
 import org.springframework.core.convert.converter.GenericConverter;
 import org.springframework.format.Formatter;
+import org.springframework.format.FormatterRegistry;
 
 /**
  * Utility to deduce the {@link ConversionService} to use for configuration properties
@@ -46,17 +46,38 @@ class ConversionServiceDeducer {
 		this.applicationContext = applicationContext;
 	}
 
-	ConversionService getConversionService() {
-		try {
-			return this.applicationContext.getBean(ConfigurableApplicationContext.CONVERSION_SERVICE_BEAN_NAME,
-					ConversionService.class);
+	List<ConversionService> getConversionServices() {
+		if (hasUserDefinedConfigurationServiceBean()) {
+			return Collections.singletonList(this.applicationContext
+					.getBean(ConfigurableApplicationContext.CONVERSION_SERVICE_BEAN_NAME, ConversionService.class));
 		}
-		catch (NoSuchBeanDefinitionException ex) {
-			return new Factory(this.applicationContext.getAutowireCapableBeanFactory()).create();
+		if (this.applicationContext instanceof ConfigurableApplicationContext) {
+			return getConversionServices((ConfigurableApplicationContext) this.applicationContext);
 		}
+		return null;
 	}
 
-	private static class Factory {
+	private List<ConversionService> getConversionServices(ConfigurableApplicationContext applicationContext) {
+		List<ConversionService> conversionServices = new ArrayList<>();
+		if (applicationContext.getBeanFactory().getConversionService() != null) {
+			conversionServices.add(applicationContext.getBeanFactory().getConversionService());
+		}
+		ConverterBeans converterBeans = new ConverterBeans(applicationContext);
+		if (!converterBeans.isEmpty()) {
+			ApplicationConversionService beansConverterService = new ApplicationConversionService();
+			converterBeans.addTo(beansConverterService);
+			conversionServices.add(beansConverterService);
+		}
+		return conversionServices;
+	}
+
+	private boolean hasUserDefinedConfigurationServiceBean() {
+		String beanName = ConfigurableApplicationContext.CONVERSION_SERVICE_BEAN_NAME;
+		return this.applicationContext.containsBean(beanName) && this.applicationContext.getAutowireCapableBeanFactory()
+				.isTypeMatch(beanName, ConversionService.class);
+	}
+
+	private static class ConverterBeans {
 
 		@SuppressWarnings("rawtypes")
 		private final List<Converter> converters;
@@ -66,17 +87,11 @@ class ConversionServiceDeducer {
 		@SuppressWarnings("rawtypes")
 		private final List<Formatter> formatters;
 
-		Factory(BeanFactory beanFactory) {
-			this.converters = beans(beanFactory, Converter.class, ConfigurationPropertiesBinding.VALUE);
-			this.genericConverters = beans(beanFactory, GenericConverter.class, ConfigurationPropertiesBinding.VALUE);
-			this.formatters = beans(beanFactory, Formatter.class, ConfigurationPropertiesBinding.VALUE);
-		}
-
-		private <T> List<T> beans(BeanFactory beanFactory, Class<T> type, String qualifier) {
-			if (beanFactory instanceof ListableBeanFactory) {
-				return beans(type, qualifier, (ListableBeanFactory) beanFactory);
-			}
-			return Collections.emptyList();
+		ConverterBeans(ConfigurableApplicationContext applicationContext) {
+			ConfigurableListableBeanFactory beanFactory = applicationContext.getBeanFactory();
+			this.converters = beans(Converter.class, ConfigurationPropertiesBinding.VALUE, beanFactory);
+			this.genericConverters = beans(GenericConverter.class, ConfigurationPropertiesBinding.VALUE, beanFactory);
+			this.formatters = beans(Formatter.class, ConfigurationPropertiesBinding.VALUE, beanFactory);
 		}
 
 		private <T> List<T> beans(Class<T> type, String qualifier, ListableBeanFactory beanFactory) {
@@ -84,21 +99,20 @@ class ConversionServiceDeducer {
 					BeanFactoryAnnotationUtils.qualifiedBeansOfType(beanFactory, type, qualifier).values());
 		}
 
-		ConversionService create() {
-			if (this.converters.isEmpty() && this.genericConverters.isEmpty() && this.formatters.isEmpty()) {
-				return ApplicationConversionService.getSharedInstance();
-			}
-			ApplicationConversionService conversionService = new ApplicationConversionService();
+		boolean isEmpty() {
+			return this.converters.isEmpty() && this.genericConverters.isEmpty() && this.formatters.isEmpty();
+		}
+
+		void addTo(FormatterRegistry registry) {
 			for (Converter<?, ?> converter : this.converters) {
-				conversionService.addConverter(converter);
+				registry.addConverter(converter);
 			}
 			for (GenericConverter genericConverter : this.genericConverters) {
-				conversionService.addConverter(genericConverter);
+				registry.addConverter(genericConverter);
 			}
 			for (Formatter<?> formatter : this.formatters) {
-				conversionService.addFormatter(formatter);
+				registry.addFormatter(formatter);
 			}
-			return conversionService;
 		}
 
 	}

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/BindConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -38,7 +38,7 @@ import org.springframework.core.convert.ConversionService;
 import org.springframework.core.convert.TypeDescriptor;
 import org.springframework.core.convert.converter.ConditionalGenericConverter;
 import org.springframework.core.convert.support.GenericConversionService;
-import org.springframework.util.Assert;
+import org.springframework.util.CollectionUtils;
 
 /**
  * Utility to handle any conversion needed during binding. This class is not thread-safe
@@ -49,125 +49,92 @@ import org.springframework.util.Assert;
  */
 final class BindConverter {
 
-	private static final Set<Class<?>> EXCLUDED_EDITORS;
-	static {
-		Set<Class<?>> excluded = new HashSet<>();
-		excluded.add(FileEditor.class); // gh-12163
-		EXCLUDED_EDITORS = Collections.unmodifiableSet(excluded);
-	}
-
 	private static BindConverter sharedInstance;
 
-	private final ConversionService conversionService;
+	private final List<ConversionService> delegates;
 
-	private BindConverter(ConversionService conversionService,
+	private BindConverter(List<ConversionService> conversionServices,
 			Consumer<PropertyEditorRegistry> propertyEditorInitializer) {
-		Assert.notNull(conversionService, "ConversionService must not be null");
-		List<ConversionService> conversionServices = getConversionServices(conversionService,
-				propertyEditorInitializer);
-		this.conversionService = new CompositeConversionService(conversionServices);
+		List<ConversionService> delegates = new ArrayList<>();
+		delegates.add(new TypeConverterConversionService(propertyEditorInitializer));
+		boolean hasApplication = false;
+		if (!CollectionUtils.isEmpty(conversionServices)) {
+			for (ConversionService conversionService : conversionServices) {
+				delegates.add(conversionService);
+				hasApplication = hasApplication || conversionService instanceof ApplicationConversionService;
+			}
+		}
+		if (!hasApplication) {
+			delegates.add(ApplicationConversionService.getSharedInstance());
+		}
+		this.delegates = Collections.unmodifiableList(delegates);
 	}
 
-	private List<ConversionService> getConversionServices(ConversionService conversionService,
-			Consumer<PropertyEditorRegistry> propertyEditorInitializer) {
-		List<ConversionService> services = new ArrayList<>();
-		services.add(new TypeConverterConversionService(propertyEditorInitializer));
-		services.add(conversionService);
-		if (!(conversionService instanceof ApplicationConversionService)) {
-			services.add(ApplicationConversionService.getSharedInstance());
-		}
-		return services;
+	boolean canConvert(Object source, ResolvableType targetType, Annotation... targetAnnotations) {
+		return canConvert(TypeDescriptor.forObject(source),
+				new ResolvableTypeDescriptor(targetType, targetAnnotations));
 	}
 
-	boolean canConvert(Object value, ResolvableType type, Annotation... annotations) {
-		return this.conversionService.canConvert(TypeDescriptor.forObject(value),
-				new ResolvableTypeDescriptor(type, annotations));
+	private boolean canConvert(TypeDescriptor sourceType, TypeDescriptor targetType) {
+		for (ConversionService service : this.delegates) {
+			if (service.canConvert(sourceType, targetType)) {
+				return true;
+			}
+		}
+		return false;
 	}
 
-	<T> T convert(Object result, Bindable<T> target) {
-		return convert(result, target.getType(), target.getAnnotations());
+	<T> T convert(Object source, Bindable<T> target) {
+		return convert(source, target.getType(), target.getAnnotations());
 	}
 
 	@SuppressWarnings("unchecked")
-	<T> T convert(Object value, ResolvableType type, Annotation... annotations) {
-		if (value == null) {
+	<T> T convert(Object source, ResolvableType targetType, Annotation... targetAnnotations) {
+		if (source == null) {
 			return null;
 		}
-		return (T) this.conversionService.convert(value, TypeDescriptor.forObject(value),
-				new ResolvableTypeDescriptor(type, annotations));
+		return (T) convert(source, TypeDescriptor.forObject(source),
+				new ResolvableTypeDescriptor(targetType, targetAnnotations));
 	}
 
-	static BindConverter get(ConversionService conversionService,
-			Consumer<PropertyEditorRegistry> propertyEditorInitializer) {
-		if (conversionService == ApplicationConversionService.getSharedInstance()
-				&& propertyEditorInitializer == null) {
-			if (sharedInstance == null) {
-				sharedInstance = new BindConverter(conversionService, propertyEditorInitializer);
+	private Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
+		for (int i = 0; i < this.delegates.size() - 1; i++) {
+			try {
+				ConversionService delegate = this.delegates.get(i);
+				if (delegate.canConvert(sourceType, targetType)) {
+					return delegate.convert(source, sourceType, targetType);
+				}
+			}
+			catch (ConversionException ex) {
 			}
-			return sharedInstance;
 		}
-		return new BindConverter(conversionService, propertyEditorInitializer);
+		return this.delegates.get(this.delegates.size() - 1).convert(source, sourceType, targetType);
 	}
 
-	/**
-	 * A {@link TypeDescriptor} backed by a {@link ResolvableType}.
-	 */
-	private static class ResolvableTypeDescriptor extends TypeDescriptor {
-
-		ResolvableTypeDescriptor(ResolvableType resolvableType, Annotation[] annotations) {
-			super(resolvableType, null, annotations);
+	static BindConverter get(List<ConversionService> conversionServices,
+			Consumer<PropertyEditorRegistry> propertyEditorInitializer) {
+		boolean sharedApplicationConversionService = (conversionServices == null) || (conversionServices.size() == 1
+				&& conversionServices.get(0) == ApplicationConversionService.getSharedInstance());
+		if (propertyEditorInitializer == null && sharedApplicationConversionService) {
+			return getSharedInstance();
 		}
+		return new BindConverter(conversionServices, propertyEditorInitializer);
+	}
 
+	private static BindConverter getSharedInstance() {
+		if (sharedInstance == null) {
+			sharedInstance = new BindConverter(null, null);
+		}
+		return sharedInstance;
 	}
 
 	/**
-	 * Composite {@link ConversionService} used to call multiple services.
+	 * A {@link TypeDescriptor} backed by a {@link ResolvableType}.
 	 */
-	static class CompositeConversionService implements ConversionService {
-
-		private final List<ConversionService> delegates;
-
-		CompositeConversionService(List<ConversionService> delegates) {
-			this.delegates = delegates;
-		}
-
-		@Override
-		public boolean canConvert(Class<?> sourceType, Class<?> targetType) {
-			Assert.notNull(targetType, "Target type to convert to cannot be null");
-			return canConvert((sourceType != null) ? TypeDescriptor.valueOf(sourceType) : null,
-					TypeDescriptor.valueOf(targetType));
-		}
-
-		@Override
-		public boolean canConvert(TypeDescriptor sourceType, TypeDescriptor targetType) {
-			for (ConversionService service : this.delegates) {
-				if (service.canConvert(sourceType, targetType)) {
-					return true;
-				}
-			}
-			return false;
-		}
-
-		@Override
-		@SuppressWarnings("unchecked")
-		public <T> T convert(Object source, Class<T> targetType) {
-			Assert.notNull(targetType, "Target type to convert to cannot be null");
-			return (T) convert(source, TypeDescriptor.forObject(source), TypeDescriptor.valueOf(targetType));
-		}
+	private static class ResolvableTypeDescriptor extends TypeDescriptor {
 
-		@Override
-		public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
-			for (int i = 0; i < this.delegates.size() - 1; i++) {
-				try {
-					ConversionService delegate = this.delegates.get(i);
-					if (delegate.canConvert(sourceType, targetType)) {
-						return delegate.convert(source, sourceType, targetType);
-					}
-				}
-				catch (ConversionException ex) {
-				}
-			}
-			return this.delegates.get(this.delegates.size() - 1).convert(source, sourceType, targetType);
+		ResolvableTypeDescriptor(ResolvableType resolvableType, Annotation[] annotations) {
+			super(resolvableType, null, annotations);
 		}
 
 	}
@@ -208,6 +175,13 @@ final class BindConverter {
 	 */
 	private static class TypeConverterConverter implements ConditionalGenericConverter {
 
+		private static final Set<Class<?>> EXCLUDED_EDITORS;
+		static {
+			Set<Class<?>> excluded = new HashSet<>();
+			excluded.add(FileEditor.class); // gh-12163
+			EXCLUDED_EDITORS = Collections.unmodifiableSet(excluded);
+		}
+
 		private final SimpleTypeConverter typeConverter;
 
 		TypeConverterConverter(SimpleTypeConverter typeConverter) {

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/Binder.java

@@ -60,9 +60,7 @@ public class Binder {
 
 	private final PlaceholdersResolver placeholdersResolver;
 
-	private final ConversionService conversionService;
-
-	private final Consumer<PropertyEditorRegistry> propertyEditorInitializer;
+	private final BindConverter bindConverter;
 
 	private final BindHandler defaultBindHandler;
 
@@ -159,12 +157,34 @@ public class Binder {
 	public Binder(Iterable<ConfigurationPropertySource> sources, PlaceholdersResolver placeholdersResolver,
 			ConversionService conversionService, Consumer<PropertyEditorRegistry> propertyEditorInitializer,
 			BindHandler defaultBindHandler, BindConstructorProvider constructorProvider) {
+		this(sources, placeholdersResolver,
+				(conversionService != null) ? Collections.singletonList(conversionService)
+						: (List<ConversionService>) null,
+				propertyEditorInitializer, defaultBindHandler, constructorProvider);
+	}
+
+	/**
+	 * Create a new {@link Binder} instance for the specified sources.
+	 * @param sources the sources used for binding
+	 * @param placeholdersResolver strategy to resolve any property placeholders
+	 * @param conversionServices the conversion services to convert values (or
+	 * {@code null} to use {@link ApplicationConversionService})
+	 * @param propertyEditorInitializer initializer used to configure the property editors
+	 * that can convert values (or {@code null} if no initialization is required). Often
+	 * used to call {@link ConfigurableListableBeanFactory#copyRegisteredEditorsTo}.
+	 * @param defaultBindHandler the default bind handler to use if none is specified when
+	 * binding
+	 * @param constructorProvider the constructor provider which provides the bind
+	 * constructor to use when binding
+	 * @since 2.5.0
+	 */
+	public Binder(Iterable<ConfigurationPropertySource> sources, PlaceholdersResolver placeholdersResolver,
+			List<ConversionService> conversionServices, Consumer<PropertyEditorRegistry> propertyEditorInitializer,
+			BindHandler defaultBindHandler, BindConstructorProvider constructorProvider) {
 		Assert.notNull(sources, "Sources must not be null");
 		this.sources = sources;
 		this.placeholdersResolver = (placeholdersResolver != null) ? placeholdersResolver : PlaceholdersResolver.NONE;
-		this.conversionService = (conversionService != null) ? conversionService
-				: ApplicationConversionService.getSharedInstance();
-		this.propertyEditorInitializer = propertyEditorInitializer;
+		this.bindConverter = BindConverter.get(conversionServices, propertyEditorInitializer);
 		this.defaultBindHandler = (defaultBindHandler != null) ? defaultBindHandler : BindHandler.DEFAULT;
 		if (constructorProvider == null) {
 			constructorProvider = BindConstructorProvider.DEFAULT;
@@ -513,8 +533,6 @@ public class Binder {
 	 */
 	final class Context implements BindContext {
 
-		private final BindConverter converter;
-
 		private int depth;
 
 		private final List<ConfigurationPropertySource> source = Arrays.asList((ConfigurationPropertySource) null);
@@ -527,10 +545,6 @@ public class Binder {
 
 		private ConfigurationProperty configurationProperty;
 
-		Context() {
-			this.converter = BindConverter.get(Binder.this.conversionService, Binder.this.propertyEditorInitializer);
-		}
-
 		private void increaseDepth() {
 			this.depth++;
 		}
@@ -602,7 +616,7 @@ public class Binder {
 		}
 
 		BindConverter getConverter() {
-			return this.converter;
+			return Binder.this.bindConverter;
 		}
 
 		@Override

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/ConfigurationPropertiesTests.java

@@ -76,6 +76,7 @@ import org.springframework.context.support.PropertySourcesPlaceholderConfigurer;
 import org.springframework.core.convert.TypeDescriptor;
 import org.springframework.core.convert.converter.Converter;
 import org.springframework.core.convert.converter.GenericConverter;
+import org.springframework.core.convert.support.DefaultConversionService;
 import org.springframework.core.env.MapPropertySource;
 import org.springframework.core.env.MutablePropertySources;
 import org.springframework.core.env.StandardEnvironment;
@@ -645,6 +646,20 @@ class ConfigurationPropertiesTests {
 		assertThat(person.lastName).isEqualTo("Smith");
 	}
 
+	@Test
+	void loadWhenBeanFactoryConversionServiceAndConverterBean() {
+		DefaultConversionService conversionService = new DefaultConversionService();
+		conversionService.addConverter(new AlienConverter());
+		this.context.getBeanFactory().setConversionService(conversionService);
+		load(new Class<?>[] { ConverterConfiguration.class, PersonAndAlienProperties.class }, "test.person=John Smith",
+				"test.alien=Alf Tanner");
+		PersonAndAlienProperties properties = this.context.getBean(PersonAndAlienProperties.class);
+		assertThat(properties.getPerson().firstName).isEqualTo("John");
+		assertThat(properties.getPerson().lastName).isEqualTo("Smith");
+		assertThat(properties.getAlien().firstName).isEqualTo("Alf");
+		assertThat(properties.getAlien().lastName).isEqualTo("Tanner");
+	}
+
 	@Test
 	void loadWhenConfigurationConverterIsNotQualifiedShouldNotConvert() {
 		assertThatExceptionOfType(BeanCreationException.class)
@@ -1908,6 +1923,32 @@ class ConfigurationPropertiesTests {
 
 	}
 
+	@EnableConfigurationProperties
+	@ConfigurationProperties(prefix = "test")
+	static class PersonAndAlienProperties {
+
+		private Person person;
+
+		private Alien alien;
+
+		Person getPerson() {
+			return this.person;
+		}
+
+		void setPerson(Person person) {
+			this.person = person;
+		}
+
+		Alien getAlien() {
+			return this.alien;
+		}
+
+		void setAlien(Alien alien) {
+			this.alien = alien;
+		}
+
+	}
+
 	@EnableConfigurationProperties
 	@ConfigurationProperties(prefix = "sample")
 	static class MapWithNumericKeyProperties {
@@ -2201,6 +2242,16 @@ class ConfigurationPropertiesTests {
 
 	}
 
+	static class AlienConverter implements Converter<String, Alien> {
+
+		@Override
+		public Alien convert(String source) {
+			String[] content = StringUtils.split(source, " ");
+			return new Alien(content[0], content[1]);
+		}
+
+	}
+
 	static class GenericPersonConverter implements GenericConverter {
 
 		@Override
@@ -2262,6 +2313,27 @@ class ConfigurationPropertiesTests {
 
 	}
 
+	static class Alien {
+
+		private final String firstName;
+
+		private final String lastName;
+
+		Alien(String firstName, String lastName) {
+			this.firstName = firstName;
+			this.lastName = lastName;
+		}
+
+		String getFirstName() {
+			return this.firstName;
+		}
+
+		String getLastName() {
+			return this.lastName;
+		}
+
+	}
+
 	static class Foo {
 
 		private String a;

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/ConversionServiceDeducerTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -18,6 +18,7 @@ package org.springframework.boot.context.properties;
 
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.util.List;
 
 import org.junit.jupiter.api.Test;
 
@@ -40,28 +41,42 @@ import static org.assertj.core.api.Assertions.assertThat;
 class ConversionServiceDeducerTests {
 
 	@Test
-	void getConversionServiceWhenHasConversionServiceBeanReturnsBean() {
+	void getConversionServicesWhenHasConversionServiceBeanContainsOnlyBean() {
 		ApplicationContext applicationContext = new AnnotationConfigApplicationContext(
 				CustomConverterServiceConfiguration.class);
 		ConversionServiceDeducer deducer = new ConversionServiceDeducer(applicationContext);
-		assertThat(deducer.getConversionService()).isInstanceOf(TestApplicationConversionService.class);
+		TestApplicationConversionService expected = applicationContext.getBean(TestApplicationConversionService.class);
+		assertThat(deducer.getConversionServices()).containsExactly(expected);
 	}
 
 	@Test
-	void getConversionServiceWhenHasNoConversionServiceBeanAndNoQualifiedBeansReturnsSharedInstance() {
+	void getConversionServiceWhenHasNoConversionServiceBeanAndNoQualifiedBeansAndNoBeanFactoryConversionServiceReturnsEmptyList() {
 		ApplicationContext applicationContext = new AnnotationConfigApplicationContext(EmptyConfiguration.class);
 		ConversionServiceDeducer deducer = new ConversionServiceDeducer(applicationContext);
-		assertThat(deducer.getConversionService()).isSameAs(ApplicationConversionService.getSharedInstance());
+		assertThat(deducer.getConversionServices()).isEmpty();
 	}
 
 	@Test
-	void getConversionServiceWhenHasQualifiedConverterBeansReturnsNewInstance() {
+	void getConversionServiceWhenHasNoConversionServiceBeanAndNoQualifiedBeansAndBeanFactoryConversionServiceContainsOnlyBeanFactoryInstance() {
+		ConfigurableApplicationContext applicationContext = new AnnotationConfigApplicationContext(
+				EmptyConfiguration.class);
+		ConversionService conversionService = new ApplicationConversionService();
+		applicationContext.getBeanFactory().setConversionService(conversionService);
+		ConversionServiceDeducer deducer = new ConversionServiceDeducer(applicationContext);
+		List<ConversionService> conversionServices = deducer.getConversionServices();
+		assertThat(conversionServices).containsOnly(conversionService);
+		assertThat(conversionServices.get(0)).isSameAs(conversionService);
+	}
+
+	@Test
+	void getConversionServiceWhenHasQualifiedConverterBeansContainsCustomizedApplicationService() {
 		ApplicationContext applicationContext = new AnnotationConfigApplicationContext(
 				CustomConverterConfiguration.class);
 		ConversionServiceDeducer deducer = new ConversionServiceDeducer(applicationContext);
-		ConversionService conversionService = deducer.getConversionService();
-		assertThat(conversionService).isNotSameAs(ApplicationConversionService.getSharedInstance());
-		assertThat(conversionService.canConvert(InputStream.class, OutputStream.class)).isTrue();
+		List<ConversionService> conversionServices = deducer.getConversionServices();
+		assertThat(conversionServices).hasSize(1);
+		assertThat(conversionServices.get(0)).isNotSameAs(ApplicationConversionService.getSharedInstance());
+		assertThat(conversionServices.get(0).canConvert(InputStream.class, OutputStream.class)).isTrue();
 	}
 
 	@Configuration(proxyBeanMethods = false)

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/bind/BindConverterTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -19,6 +19,7 @@ package org.springframework.boot.context.properties.bind;
 import java.beans.PropertyEditorSupport;
 import java.io.File;
 import java.time.Duration;
+import java.util.Collections;
 import java.util.List;
 import java.util.function.Consumer;
 
@@ -28,7 +29,6 @@ import org.mockito.Mock;
 import org.mockito.junit.jupiter.MockitoExtension;
 
 import org.springframework.beans.PropertyEditorRegistry;
-import org.springframework.boot.convert.ApplicationConversionService;
 import org.springframework.core.ResolvableType;
 import org.springframework.core.convert.ConversionService;
 import org.springframework.core.convert.ConverterNotFoundException;
@@ -38,7 +38,6 @@ import org.springframework.core.convert.support.GenericConversionService;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.verify;
 
@@ -54,20 +53,14 @@ class BindConverterTests {
 	@Mock
 	private Consumer<PropertyEditorRegistry> propertyEditorInitializer;
 
-	@Test
-	void createWhenConversionServiceIsNullShouldThrowException() {
-		assertThatIllegalArgumentException().isThrownBy(() -> BindConverter.get(null, null))
-				.withMessageContaining("ConversionService must not be null");
-	}
-
 	@Test
 	void createWhenPropertyEditorInitializerIsNullShouldCreate() {
-		BindConverter.get(ApplicationConversionService.getSharedInstance(), null);
+		BindConverter.get(null, null);
 	}
 
 	@Test
 	void createWhenPropertyEditorInitializerIsNotNullShouldUseToInitialize() {
-		BindConverter.get(ApplicationConversionService.getSharedInstance(), this.propertyEditorInitializer);
+		BindConverter.get(null, this.propertyEditorInitializer);
 		verify(this.propertyEditorInitializer).accept(any(PropertyEditorRegistry.class));
 	}
 
@@ -111,7 +104,7 @@ class BindConverterTests {
 
 	@Test
 	void canConvertWhenNotPropertyEditorAndConversionServiceCannotConvertShouldReturnFalse() {
-		BindConverter bindConverter = BindConverter.get(ApplicationConversionService.getSharedInstance(), null);
+		BindConverter bindConverter = BindConverter.get(null, null);
 		assertThat(bindConverter.canConvert("test", ResolvableType.forClass(SampleType.class))).isFalse();
 	}
 
@@ -162,7 +155,7 @@ class BindConverterTests {
 
 	@Test
 	void convertWhenNotPropertyEditorAndConversionServiceCannotConvertShouldThrowException() {
-		BindConverter bindConverter = BindConverter.get(ApplicationConversionService.getSharedInstance(), null);
+		BindConverter bindConverter = BindConverter.get(null, null);
 		assertThatExceptionOfType(ConverterNotFoundException.class)
 				.isThrownBy(() -> bindConverter.convert("test", ResolvableType.forClass(SampleType.class)));
 	}
@@ -171,27 +164,29 @@ class BindConverterTests {
 	void convertWhenConvertingToFileShouldExcludeFileEditor() {
 		// For back compatibility we want true file conversion and not an accidental
 		// classpath resource reference. See gh-12163
-		BindConverter bindConverter = BindConverter.get(new GenericConversionService(), null);
+		BindConverter bindConverter = BindConverter.get(Collections.singletonList(new GenericConversionService()),
+				null);
 		File result = bindConverter.convert(".", ResolvableType.forClass(File.class));
 		assertThat(result.getPath()).isEqualTo(".");
 	}
 
 	@Test
 	void fallsBackToApplicationConversionService() {
-		BindConverter bindConverter = BindConverter.get(new GenericConversionService(), null);
+		BindConverter bindConverter = BindConverter.get(Collections.singletonList(new GenericConversionService()),
+				null);
 		Duration result = bindConverter.convert("10s", ResolvableType.forClass(Duration.class));
 		assertThat(result.getSeconds()).isEqualTo(10);
 	}
 
 	private BindConverter getPropertyEditorOnlyBindConverter(
 			Consumer<PropertyEditorRegistry> propertyEditorInitializer) {
-		return BindConverter.get(new ThrowingConversionService(), propertyEditorInitializer);
+		return BindConverter.get(Collections.singletonList(new ThrowingConversionService()), propertyEditorInitializer);
 	}
 
 	private BindConverter getBindConverter(Converter<?, ?> converter) {
 		GenericConversionService conversionService = new GenericConversionService();
 		conversionService.addConverter(converter);
-		return BindConverter.get(conversionService, null);
+		return BindConverter.get(Collections.singletonList(conversionService), null);
 	}
 
 	private void registerSampleTypeEditor(PropertyEditorRegistry registry) {

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/bind/JavaBeanBinderTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -38,6 +38,7 @@ import org.springframework.boot.context.properties.source.ConfigurationPropertyS
 import org.springframework.boot.context.properties.source.MockConfigurationPropertySource;
 import org.springframework.boot.convert.Delimiter;
 import org.springframework.core.ResolvableType;
+import org.springframework.core.convert.ConversionService;
 import org.springframework.format.annotation.DateTimeFormat;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -340,7 +341,7 @@ class JavaBeanBinderTests {
 
 	@Test
 	void bindToInstanceWhenNoDefaultConstructorShouldBind() {
-		Binder binder = new Binder(this.sources, null, null, null, null,
+		Binder binder = new Binder(this.sources, null, (ConversionService) null, null, null,
 				(bindable, isNestedConstructorBinding) -> null);
 		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
 		source.put("foo.value", "bar");

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/bind/ValueObjectBinderTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -31,6 +31,7 @@ import org.springframework.boot.context.properties.source.ConfigurationPropertyN
 import org.springframework.boot.context.properties.source.ConfigurationPropertySource;
 import org.springframework.boot.context.properties.source.MockConfigurationPropertySource;
 import org.springframework.core.ResolvableType;
+import org.springframework.core.convert.ConversionService;
 import org.springframework.format.annotation.DateTimeFormat;
 import org.springframework.util.Assert;
 
@@ -109,7 +110,7 @@ class ValueObjectBinderTests {
 		this.sources.add(source);
 		Constructor<?>[] constructors = MultipleConstructorsBean.class.getDeclaredConstructors();
 		Constructor<?> constructor = (constructors[0].getParameterCount() == 1) ? constructors[0] : constructors[1];
-		Binder binder = new Binder(this.sources, null, null, null, null,
+		Binder binder = new Binder(this.sources, null, (ConversionService) null, null, null,
 				(bindable, isNestedConstructorBinding) -> constructor);
 		MultipleConstructorsBean bound = binder.bind("foo", Bindable.of(MultipleConstructorsBean.class)).get();
 		assertThat(bound.getIntValue()).isEqualTo(12);