Use shared BindConverter when possible

Update the `Binder` so that a single shares static `BindConverter` is
used whenever possible.

Closes gh-14562

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

@@ -47,7 +47,7 @@ import org.springframework.util.Assert;
  * @author Phillip Webb
  * @author Andy Wilkinson
  */
-class BindConverter {
+final class BindConverter {
 
 	private static final Set<Class<?>> EXCLUDED_EDITORS;
 	static {
@@ -56,9 +56,11 @@ class BindConverter {
 		EXCLUDED_EDITORS = Collections.unmodifiableSet(excluded);
 	}
 
+	private static BindConverter sharedInstance;
+
 	private final ConversionService conversionService;
 
-	BindConverter(ConversionService conversionService,
+	private BindConverter(ConversionService conversionService,
 			Consumer<PropertyEditorRegistry> propertyEditorInitializer) {
 		Assert.notNull(conversionService, "ConversionService must not be null");
 		List<ConversionService> conversionServices = getConversionServices(
@@ -97,6 +99,21 @@ class BindConverter {
 				new ResolvableTypeDescriptor(type, annotations));
 	}
 
+	public static BindConverter get(ConversionService conversionService,
+			Consumer<PropertyEditorRegistry> propertyEditorInitializer) {
+		if (conversionService == ApplicationConversionService.getSharedInstance()
+				&& propertyEditorInitializer == null) {
+			BindConverter instance = sharedInstance;
+			if (instance == null) {
+				instance = new BindConverter(conversionService,
+						propertyEditorInitializer);
+				sharedInstance = instance;
+			}
+			return instance;
+		}
+		return new BindConverter(conversionService, propertyEditorInitializer);
+	}
+
 	/**
 	 * A {@link TypeDescriptor} backed by a {@link ResolvableType}.
 	 */

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

@@ -392,7 +392,7 @@ public class Binder {
 		private ConfigurationProperty configurationProperty;
 
 		Context() {
-			this.converter = new BindConverter(Binder.this.conversionService,
+			this.converter = BindConverter.get(Binder.this.conversionService,
 					Binder.this.propertyEditorInitializer);
 		}
 

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

@@ -65,17 +65,17 @@ public class BindConverterTests {
 	public void createWhenConversionServiceIsNullShouldThrowException() {
 		this.thrown.expect(IllegalArgumentException.class);
 		this.thrown.expectMessage("ConversionService must not be null");
-		new BindConverter(null, null);
+		BindConverter.get(null, null);
 	}
 
 	@Test
 	public void createWhenPropertyEditorInitializerIsNullShouldCreate() {
-		new BindConverter(ApplicationConversionService.getSharedInstance(), null);
+		BindConverter.get(ApplicationConversionService.getSharedInstance(), null);
 	}
 
 	@Test
 	public void createWhenPropertyEditorInitializerIsNotNullShouldUseToInitialize() {
-		new BindConverter(ApplicationConversionService.getSharedInstance(),
+		BindConverter.get(ApplicationConversionService.getSharedInstance(),
 				this.propertyEditorInitializer);
 		verify(this.propertyEditorInitializer).accept(any(PropertyEditorRegistry.class));
 	}
@@ -128,8 +128,8 @@ public class BindConverterTests {
 
 	@Test
 	public void canConvertWhenNotPropertyEditorAndConversionServiceCannotConvertShouldReturnFalse() {
-		BindConverter bindConverter = new BindConverter(
-				ApplicationConversionService.getSharedInstance(), null);
+		BindConverter bindConverter = BindConverter
+				.get(ApplicationConversionService.getSharedInstance(), null);
 		assertThat(bindConverter.canConvert("test",
 				ResolvableType.forClass(SampleType.class))).isFalse();
 	}
@@ -189,8 +189,8 @@ public class BindConverterTests {
 
 	@Test
 	public void convertWhenNotPropertyEditorAndConversionServiceCannotConvertShouldThrowException() {
-		BindConverter bindConverter = new BindConverter(
-				ApplicationConversionService.getSharedInstance(), null);
+		BindConverter bindConverter = BindConverter
+				.get(ApplicationConversionService.getSharedInstance(), null);
 		this.thrown.expect(ConverterNotFoundException.class);
 		bindConverter.convert("test", ResolvableType.forClass(SampleType.class));
 	}
@@ -199,7 +199,7 @@ public class BindConverterTests {
 	public void convertWhenConvertingToFileShouldExcludeFileEditor() {
 		// For back compatibility we want true file conversion and not an accidental
 		// classpath resource reference. See gh-12163
-		BindConverter bindConverter = new BindConverter(new GenericConversionService(),
+		BindConverter bindConverter = BindConverter.get(new GenericConversionService(),
 				null);
 		File result = bindConverter.convert(".", ResolvableType.forClass(File.class));
 		assertThat(result.getPath()).isEqualTo(".");
@@ -207,7 +207,7 @@ public class BindConverterTests {
 
 	@Test
 	public void fallsBackToApplicationConversionService() {
-		BindConverter bindConverter = new BindConverter(new GenericConversionService(),
+		BindConverter bindConverter = BindConverter.get(new GenericConversionService(),
 				null);
 		Duration result = bindConverter.convert("10s",
 				ResolvableType.forClass(Duration.class));
@@ -216,14 +216,14 @@ public class BindConverterTests {
 
 	private BindConverter getPropertyEditorOnlyBindConverter(
 			Consumer<PropertyEditorRegistry> propertyEditorInitializer) {
-		return new BindConverter(new ThrowingConversionService(),
+		return BindConverter.get(new ThrowingConversionService(),
 				propertyEditorInitializer);
 	}
 
 	private BindConverter getBindConverter(Converter<?, ?> converter) {
 		GenericConversionService conversionService = new GenericConversionService();
 		conversionService.addConverter(converter);
-		return new BindConverter(conversionService, null);
+		return BindConverter.get(conversionService, null);
 	}
 
 	private void registerSampleTypeEditor(PropertyEditorRegistry registry) {