Fix @DefaultValue PropertyEditor based conversion

Update `ValueObjectBinder` reattempt conversion if the `@DefaultValue`
contains a single element. Prior to this commit, single element
conversion relied on the `ArrayToObjectConverter` which isn't always
available.

Fixes gh-21264

Author: philwebb

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

@@ -36,6 +36,7 @@
 import org.springframework.core.MethodParameter;
 import org.springframework.core.ParameterNameDiscoverer;
 import org.springframework.core.ResolvableType;
+import org.springframework.core.convert.ConversionException;
 import org.springframework.util.Assert;
 
 /**
@@ -94,16 +95,30 @@ private <T> T getDefaultValue(Binder.Context context, ConstructorParameter param
 		Annotation[] annotations = parameter.getAnnotations();
 		for (Annotation annotation : annotations) {
 			if (annotation instanceof DefaultValue) {
-				DefaultValue defaultValue = (DefaultValue) annotation;
-				if (defaultValue.value().length == 0) {
+				String[] defaultValue = ((DefaultValue) annotation).value();
+				if (defaultValue.length == 0) {
 					return getNewInstanceIfPossible(context, type);
 				}
-				return context.getConverter().convert(defaultValue.value(), type, annotations);
+				return convertDefaultValue(context.getConverter(), defaultValue, type, annotations);
 			}
 		}
 		return null;
 	}
 
+	private <T> T convertDefaultValue(BindConverter converter, String[] defaultValue, ResolvableType type,
+			Annotation[] annotations) {
+		try {
+			return converter.convert(defaultValue, type, annotations);
+		}
+		catch (ConversionException ex) {
+			// Try again in case ArrayToObjectConverter is not in play
+			if (defaultValue.length == 1) {
+				return converter.convert(defaultValue[0], type, annotations);
+			}
+			throw ex;
+		}
+	}
+
 	@SuppressWarnings("unchecked")
 	private <T> T getNewInstanceIfPossible(Binder.Context context, ResolvableType type) {
 		Class<T> resolved = (Class<T>) type.resolve();

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

@@ -16,6 +16,8 @@
 package org.springframework.boot.context.properties.bind;
 
 import java.lang.reflect.Constructor;
+import java.nio.file.Path;
+import java.nio.file.Paths;
 import java.time.LocalDate;
 import java.util.ArrayList;
 import java.util.List;
@@ -307,6 +309,29 @@ void bindWhenPrimitiveParameterWithEmptyDefaultValueShouldThrowException() {
 				.withStackTraceContaining("Parameter of type int must have a non-empty default value.");
 	}
 
+	@Test
+	void bindWhenBindingToPathTypeWithValue() { // gh-21263
+		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
+		source.put("test.name", "test");
+		source.put("test.path", "specific_value");
+		this.sources.add(source);
+		Bindable<PathBean> target = Bindable.of(PathBean.class);
+		PathBean bound = this.binder.bind("test", target).get();
+		assertThat(bound.getName()).isEqualTo("test");
+		assertThat(bound.getPath()).isEqualTo(Paths.get("specific_value"));
+	}
+
+	@Test
+	void bindWhenBindingToPathTypeWithDefaultValue() { // gh-21263
+		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
+		source.put("test.name", "test");
+		this.sources.add(source);
+		Bindable<PathBean> target = Bindable.of(PathBean.class);
+		PathBean bound = this.binder.bindOrCreate("test", target);
+		assertThat(bound.getName()).isEqualTo("test");
+		assertThat(bound.getPath()).isEqualTo(Paths.get("default_value"));
+	}
+
 	private void noConfigurationProperty(BindException ex) {
 		assertThat(ex.getProperty()).isNull();
 	}
@@ -684,4 +709,25 @@ int getIntValue() {
 
 	}
 
+	static class PathBean {
+
+		private final String name;
+
+		private final Path path;
+
+		PathBean(String name, @DefaultValue("default_value") Path path) {
+			this.name = name;
+			this.path = path;
+		}
+
+		String getName() {
+			return this.name;
+		}
+
+		Path getPath() {
+			return this.path;
+		}
+
+	}
+
 }