Support Formatter conversion service beans

Update `ConversionServiceDeducer` to also include `Formatter` beans
when they are qualified with `@ConfigurationPropertiesBinding`.

Fixes gh-23576

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

@@ -30,6 +30,7 @@ import org.springframework.context.ConfigurableApplicationContext;
 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;
 
 /**
  * Utility to deduce the {@link ConversionService} to use for configuration properties
@@ -62,9 +63,13 @@ class ConversionServiceDeducer {
 
 		private final List<GenericConverter> genericConverters;
 
+		@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) {
@@ -80,7 +85,7 @@ class ConversionServiceDeducer {
 		}
 
 		public ConversionService create() {
-			if (this.converters.isEmpty() && this.genericConverters.isEmpty()) {
+			if (this.converters.isEmpty() && this.genericConverters.isEmpty() && this.formatters.isEmpty()) {
 				return ApplicationConversionService.getSharedInstance();
 			}
 			ApplicationConversionService conversionService = new ApplicationConversionService();
@@ -90,6 +95,9 @@ class ConversionServiceDeducer {
 			for (GenericConverter genericConverter : this.genericConverters) {
 				conversionService.addConverter(genericConverter);
 			}
+			for (Formatter<?> formatter : this.formatters) {
+				conversionService.addFormatter(formatter);
+			}
 			return conversionService;
 		}
 

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

@@ -18,12 +18,14 @@ package org.springframework.boot.context.properties;
 
 import java.beans.PropertyEditorSupport;
 import java.io.File;
+import java.text.ParseException;
 import java.time.Duration;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.LinkedHashMap;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Properties;
 import java.util.Set;
@@ -66,6 +68,7 @@ import org.springframework.core.io.ClassPathResource;
 import org.springframework.core.io.ProtocolResolver;
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.ResourceLoader;
+import org.springframework.format.Formatter;
 import org.springframework.mock.env.MockEnvironment;
 import org.springframework.stereotype.Component;
 import org.springframework.test.context.support.TestPropertySourceUtils;
@@ -597,7 +600,7 @@ public class ConfigurationPropertiesTests {
 	}
 
 	@Test
-	public void loadShouldUseConfigurationConverter() {
+	public void loadShouldUseConverterBean() {
 		prepareConverterContext(ConverterConfiguration.class, PersonProperties.class);
 		Person person = this.context.getBean(PersonProperties.class).getPerson();
 		assertThat(person.firstName).isEqualTo("John");
@@ -613,13 +616,21 @@ public class ConfigurationPropertiesTests {
 	}
 
 	@Test
-	public void loadShouldUseGenericConfigurationConverter() {
+	public void loadShouldUseGenericConverterBean() {
 		prepareConverterContext(GenericConverterConfiguration.class, PersonProperties.class);
 		Person person = this.context.getBean(PersonProperties.class).getPerson();
 		assertThat(person.firstName).isEqualTo("John");
 		assertThat(person.lastName).isEqualTo("Smith");
 	}
 
+	@Test
+	public void loadShouldUseFormatterBean() {
+		prepareConverterContext(FormatterConfiguration.class, PersonProperties.class);
+		Person person = this.context.getBean(PersonProperties.class).getPerson();
+		assertThat(person.firstName).isEqualTo("John");
+		assertThat(person.lastName).isEqualTo("Smith");
+	}
+
 	@Test
 	public void loadWhenGenericConfigurationConverterIsNotQualifiedShouldNotConvert() {
 		assertThatExceptionOfType(BeanCreationException.class).isThrownBy(
@@ -1043,6 +1054,17 @@ public class ConfigurationPropertiesTests {
 
 	}
 
+	@Configuration
+	static class FormatterConfiguration {
+
+		@Bean
+		@ConfigurationPropertiesBinding
+		Formatter<Person> personFormatter() {
+			return new PersonFormatter();
+		}
+
+	}
+
 	@Configuration
 	static class NonQualifiedGenericConverterConfiguration {
 
@@ -1731,12 +1753,27 @@ public class ConfigurationPropertiesTests {
 
 	}
 
+	static class PersonFormatter implements Formatter<Person> {
+
+		@Override
+		public String print(Person person, Locale locale) {
+			return person.getFirstName() + " " + person.getLastName();
+		}
+
+		@Override
+		public Person parse(String text, Locale locale) throws ParseException {
+			String[] content = text.split(" ");
+			return new Person(content[0], content[1]);
+		}
+
+	}
+
 	static class PersonPropertyEditor extends PropertyEditorSupport {
 
 		@Override
 		public void setAsText(String text) throws IllegalArgumentException {
-			String[] split = text.split(",");
-			setValue(new Person(split[1], split[0]));
+			String[] content = text.split(",");
+			setValue(new Person(content[1], content[0]));
 		}
 
 	}
@@ -1752,6 +1789,14 @@ public class ConfigurationPropertiesTests {
 			this.lastName = lastName;
 		}
 
+		String getFirstName() {
+			return this.firstName;
+		}
+
+		String getLastName() {
+			return this.lastName;
+		}
+
 	}
 
 	static class Foo {