Add @name support for value object binding

Update value object binder support so that parameters can be annotated
with `@Name` if a specific property name should be used. Prior to this
commit is was not possible to use Java reserved words as property names.

Closes gh-22492

Author: philwebb

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

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2012-2020 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.context.properties.bind;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Annotation that can be used to specify the name when binding to an immutable property.
+ * This annotation may be required when binding to names that clash with reserved language
+ * keywords.
+ *
+ * @author Phillip Webb
+ * @since 2.4.0
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ ElementType.PARAMETER })
+@Documented
+public @interface Name {
+
+	/**
+	 * The name of the property to use for binding.
+	 * @return the property name
+	 */
+	String value();
+
+}

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

@@ -36,6 +36,8 @@
 import org.springframework.core.MethodParameter;
 import org.springframework.core.ParameterNameDiscoverer;
 import org.springframework.core.ResolvableType;
+import org.springframework.core.annotation.MergedAnnotation;
+import org.springframework.core.annotation.MergedAnnotations;
 import org.springframework.core.convert.ConversionException;
 import org.springframework.util.Assert;
 
@@ -245,7 +247,8 @@ private static List<ConstructorParameter> parseConstructorParameters(Constructor
 			Parameter[] parameters = constructor.getParameters();
 			List<ConstructorParameter> result = new ArrayList<>(parameters.length);
 			for (int i = 0; i < parameters.length; i++) {
-				String name = names[i];
+				String name = MergedAnnotations.from(parameters[i]).get(Name.class)
+						.getValue(MergedAnnotation.VALUE, String.class).orElse(names[i]);
 				ResolvableType parameterType = ResolvableType.forMethodParameter(new MethodParameter(constructor, i),
 						type);
 				Annotation[] annotations = parameters[i].getDeclaredAnnotations();

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

@@ -40,6 +40,7 @@
  * Tests for {@link ValueObjectBinder}.
  *
  * @author Madhura Bhave
+ * @author Phillip Webb
  */
 class ValueObjectBinderTests {
 
@@ -332,6 +333,17 @@ void bindWhenBindingToPathTypeWithDefaultValue() { // gh-21263
 		assertThat(bound.getPath()).isEqualTo(Paths.get("default_value"));
 	}
 
+	@Test
+	void bindToAnnotationNamedParameter() {
+		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
+		source.put("test.import", "test");
+		this.sources.add(source);
+		Bindable<NamedParameter> target = Bindable.of(NamedParameter.class);
+		NamedParameter bound = this.binder.bindOrCreate("test", target);
+		assertThat(bound.getImportName()).isEqualTo("test");
+
+	}
+
 	private void noConfigurationProperty(BindException ex) {
 		assertThat(ex.getProperty()).isNull();
 	}
@@ -730,4 +742,18 @@ Path getPath() {
 
 	}
 
+	static class NamedParameter {
+
+		private final String importName;
+
+		NamedParameter(@Name("import") String importName) {
+			this.importName = importName;
+		}
+
+		String getImportName() {
+			return this.importName;
+		}
+
+	}
+
 }