Polish Binder classes

Polish and rename some of the internal Binder classes to better reflect
their purpose. The `BeanBinder` is now called `DataObjectBinder` and
as a `JavaBeanBinder` implementation for setter based properties, and
a `ValueObjectBinder` implementation for constructor based properties.

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

@@ -55,7 +55,7 @@ public class Binder {
 	private static final Set<Class<?>> NON_BEAN_CLASSES = Collections
 			.unmodifiableSet(new HashSet<>(Arrays.asList(Object.class, Class.class)));
 
-	private static final BeanBinder[] BEAN_BINDERS = { new ConstructorParametersBinder(), new JavaBeanBinder() };
+	private static final DataObjectBinder[] DATA_OBJECT_BINDERS = { new ValueObjectBinder(), new JavaBeanBinder() };
 
 	private final Iterable<ConfigurationPropertySource> sources;
 
@@ -282,7 +282,7 @@ public class Binder {
 			result = context.getConverter().convert(result, target);
 		}
 		if (result == null && create) {
-			result = createBean(target, context);
+			result = create(target, context);
 			result = handler.onCreate(name, target, context, result);
 			result = context.getConverter().convert(result, target);
 			Assert.state(result != null, () -> "Unable to create instance for " + target.getType());
@@ -291,12 +291,11 @@ public class Binder {
 		return context.getConverter().convert(result, target);
 	}
 
-	private Object createBean(Bindable<?> target, Context context) {
-		Class<?> type = target.getType().resolve();
-		for (BeanBinder beanBinder : BEAN_BINDERS) {
-			Object bean = beanBinder.create(type, context);
-			if (bean != null) {
-				return bean;
+	private Object create(Bindable<?> target, Context context) {
+		for (DataObjectBinder dataObjectBinder : DATA_OBJECT_BINDERS) {
+			Object instance = dataObjectBinder.create(target, context);
+			if (instance != null) {
+				return instance;
 			}
 		}
 		return null;
@@ -331,15 +330,15 @@ public class Binder {
 				return bindProperty(target, context, property);
 			}
 			catch (ConverterNotFoundException ex) {
-				// We might still be able to bind it as a bean
-				Object bean = bindBean(name, target, handler, context, allowRecursiveBinding);
-				if (bean != null) {
-					return bean;
+				// We might still be able to bind it using the recursive binders
+				Object instance = bindDataObject(name, target, handler, context, allowRecursiveBinding);
+				if (instance != null) {
+					return instance;
 				}
 				throw ex;
 			}
 		}
-		return bindBean(name, target, handler, context, allowRecursiveBinding);
+		return bindDataObject(name, target, handler, context, allowRecursiveBinding);
 	}
 
 	private AggregateBinder<?> getAggregateBinder(Bindable<?> target, Context context) {
@@ -387,22 +386,22 @@ public class Binder {
 		return result;
 	}
 
-	private Object bindBean(ConfigurationPropertyName name, Bindable<?> target, BindHandler handler, Context context,
-			boolean allowRecursiveBinding) {
+	private Object bindDataObject(ConfigurationPropertyName name, Bindable<?> target, BindHandler handler,
+			Context context, boolean allowRecursiveBinding) {
 		if (isUnbindableBean(name, target, context)) {
 			return null;
 		}
 		Class<?> type = target.getType().resolve(Object.class);
-		if (!allowRecursiveBinding && context.hasBoundBean(type)) {
+		if (!allowRecursiveBinding && context.isBindingDataObject(type)) {
 			return null;
 		}
-		BeanPropertyBinder propertyBinder = (propertyName, propertyTarget) -> bind(name.append(propertyName),
+		DataObjectPropertyBinder propertyBinder = (propertyName, propertyTarget) -> bind(name.append(propertyName),
 				propertyTarget, handler, context, false, false);
-		return context.withBean(type, () -> {
-			for (BeanBinder beanBinder : BEAN_BINDERS) {
-				Object bean = beanBinder.bind(name, target, context, propertyBinder);
-				if (bean != null) {
-					return bean;
+		return context.withDataObject(type, () -> {
+			for (DataObjectBinder dataObjectBinder : DATA_OBJECT_BINDERS) {
+				Object instance = dataObjectBinder.bind(name, target, context, propertyBinder);
+				if (instance != null) {
+					return instance;
 				}
 			}
 			return null;
@@ -457,7 +456,7 @@ public class Binder {
 
 		private int sourcePushCount;
 
-		private final Deque<Class<?>> beans = new ArrayDeque<>();
+		private final Deque<Class<?>> dataObjectBindings = new ArrayDeque<>();
 
 		private ConfigurationProperty configurationProperty;
 
@@ -487,18 +486,18 @@ public class Binder {
 			}
 		}
 
-		private <T> T withBean(Class<?> bean, Supplier<T> supplier) {
-			this.beans.push(bean);
+		private <T> T withDataObject(Class<?> type, Supplier<T> supplier) {
+			this.dataObjectBindings.push(type);
 			try {
 				return withIncreasedDepth(supplier);
 			}
 			finally {
-				this.beans.pop();
+				this.dataObjectBindings.pop();
 			}
 		}
 
-		private boolean hasBoundBean(Class<?> bean) {
-			return this.beans.contains(bean);
+		private boolean isBindingDataObject(Class<?> type) {
+			return this.dataObjectBindings.contains(type);
 		}
 
 		private <T> T withIncreasedDepth(Supplier<T> supplier) {

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/BeanBinder.java → spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/DataObjectBinder.java

@@ -20,15 +20,18 @@ import org.springframework.boot.context.properties.bind.Binder.Context;
 import org.springframework.boot.context.properties.source.ConfigurationPropertyName;
 
 /**
- * Internal strategy used by {@link Binder} to bind beans.
+ * Internal strategy used by {@link Binder} to bind data objects. A data object is an
+ * object composed itself of recursively bound properties.
  *
  * @author Phillip Webb
  * @author Madhura Bhave
+ * @see JavaBeanBinder
+ * @see ValueObjectBinder
  */
-interface BeanBinder {
+interface DataObjectBinder {
 
 	/**
-	 * Return a bound bean instance or {@code null} if the {@link BeanBinder} does not
+	 * Return a bound instance or {@code null} if the {@link DataObjectBinder} does not
 	 * support the specified {@link Bindable}.
 	 * @param name the name being bound
 	 * @param target the bindable to bind
@@ -37,15 +40,17 @@ interface BeanBinder {
 	 * @param <T> the source type
 	 * @return a bound instance or {@code null}
 	 */
-	<T> T bind(ConfigurationPropertyName name, Bindable<T> target, Context context, BeanPropertyBinder propertyBinder);
+	<T> T bind(ConfigurationPropertyName name, Bindable<T> target, Context context,
+			DataObjectPropertyBinder propertyBinder);
 
 	/**
-	 * Return a new instance for the specified type.
-	 * @param type the type used for creating a new instance
+	 * Return a newly created instance or {@code null} if the {@link DataObjectBinder}
+	 * does not support the specified {@link Bindable}.
+	 * @param target the bindable to create
 	 * @param context the bind context
 	 * @param <T> the source type
 	 * @return the created instance
 	 */
-	<T> T create(Class<T> type, Context context);
+	<T> T create(Bindable<T> target, Context context);
 
 }

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/BeanPropertyBinder.java → spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/DataObjectPropertyBinder.java

@@ -17,13 +17,13 @@
 package org.springframework.boot.context.properties.bind;
 
 /**
- * Binder that can be used by {@link BeanBinder} implementations to recursively bind bean
- * properties.
+ * Binder that can be used by {@link DataObjectBinder} implementations to bind the data
+ * object properties.
  *
  * @author Phillip Webb
  * @author Madhura Bhave
  */
-interface BeanPropertyBinder {
+interface DataObjectPropertyBinder {
 
 	/**
 	 * Bind the given property.

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/BeanPropertyName.java → spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/DataObjectPropertyName.java

@@ -17,14 +17,15 @@
 package org.springframework.boot.context.properties.bind;
 
 /**
- * Internal utility to help when dealing with Java Bean property names.
+ * Internal utility to help when dealing with data object property names.
  *
  * @author Phillip Webb
  * @author Madhura Bhave
+ * @see DataObjectBinder
  */
-abstract class BeanPropertyName {
+abstract class DataObjectPropertyName {
 
-	private BeanPropertyName() {
+	private DataObjectPropertyName() {
 	}
 
 	/**
@@ -33,19 +34,9 @@ abstract class BeanPropertyName {
 	 * @return the dashed from
 	 */
 	public static String toDashedForm(String name) {
-		return toDashedForm(name, 0);
-	}
-
-	/**
-	 * Return the specified Java Bean property name in dashed form.
-	 * @param name the source name
-	 * @param start the starting char
-	 * @return the dashed from
-	 */
-	public static String toDashedForm(String name, int start) {
 		StringBuilder result = new StringBuilder();
 		String replaced = name.replace('_', '-');
-		for (int i = start; i < replaced.length(); i++) {
+		for (int i = 0; i < replaced.length(); i++) {
 			char ch = replaced.charAt(i);
 			if (Character.isUpperCase(ch) && result.length() > 0 && result.charAt(result.length() - 1) != '-') {
 				result.append('-');

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

@@ -35,16 +35,16 @@ import org.springframework.core.MethodParameter;
 import org.springframework.core.ResolvableType;
 
 /**
- * {@link BeanBinder} for mutable Java Beans.
+ * {@link DataObjectBinder} for mutable Java Beans.
  *
  * @author Phillip Webb
  * @author Madhura Bhave
  */
-class JavaBeanBinder implements BeanBinder {
+class JavaBeanBinder implements DataObjectBinder {
 
 	@Override
 	public <T> T bind(ConfigurationPropertyName name, Bindable<T> target, Context context,
-			BeanPropertyBinder propertyBinder) {
+			DataObjectPropertyBinder propertyBinder) {
 		boolean hasKnownBindableProperties = hasKnownBindableProperties(name, context);
 		Bean<T> bean = Bean.get(target, hasKnownBindableProperties);
 		if (bean == null) {
@@ -56,8 +56,10 @@ class JavaBeanBinder implements BeanBinder {
 	}
 
 	@Override
-	public <T> T create(Class<T> type, Context context) {
-		return BeanUtils.instantiateClass(type);
+	@SuppressWarnings("unchecked")
+	public <T> T create(Bindable<T> target, Context context) {
+		Class<T> type = (Class<T>) target.getType().resolve();
+		return (type != null) ? BeanUtils.instantiateClass(type) : null;
 	}
 
 	private boolean hasKnownBindableProperties(ConfigurationPropertyName name, Context context) {
@@ -69,7 +71,7 @@ class JavaBeanBinder implements BeanBinder {
 		return false;
 	}
 
-	private <T> boolean bind(BeanPropertyBinder propertyBinder, Bean<T> bean, BeanSupplier<T> beanSupplier) {
+	private <T> boolean bind(DataObjectPropertyBinder propertyBinder, Bean<T> bean, BeanSupplier<T> beanSupplier) {
 		boolean bound = false;
 		for (BeanProperty beanProperty : bean.getProperties().values()) {
 			bound |= bind(beanSupplier, propertyBinder, beanProperty);
@@ -77,7 +79,8 @@ class JavaBeanBinder implements BeanBinder {
 		return bound;
 	}
 
-	private <T> boolean bind(BeanSupplier<T> beanSupplier, BeanPropertyBinder propertyBinder, BeanProperty property) {
+	private <T> boolean bind(BeanSupplier<T> beanSupplier, DataObjectPropertyBinder propertyBinder,
+			BeanProperty property) {
 		String propertyName = property.getName();
 		ResolvableType type = property.getType();
 		Supplier<Object> value = property.getValue(beanSupplier);
@@ -268,7 +271,7 @@ class JavaBeanBinder implements BeanBinder {
 		private Field field;
 
 		BeanProperty(String name, ResolvableType declaringClassType) {
-			this.name = BeanPropertyName.toDashedForm(name);
+			this.name = DataObjectPropertyName.toDashedForm(name);
 			this.declaringClassType = declaringClassType;
 		}
 

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/bind/BeanPropertyNameTests.java → spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/bind/DataObjectPropertyNameTests.java

@@ -21,21 +21,21 @@ import org.junit.jupiter.api.Test;
 import static org.assertj.core.api.Assertions.assertThat;
 
 /**
- * Tests for {@link BeanPropertyName}.
+ * Tests for {@link DataObjectPropertyName}.
  *
  * @author Phillip Webb
  * @author Madhura Bhave
  */
-class BeanPropertyNameTests {
+class DataObjectPropertyNameTests {
 
 	@Test
 	void toDashedCaseShouldConvertValue() {
-		assertThat(BeanPropertyName.toDashedForm("Foo")).isEqualTo("foo");
-		assertThat(BeanPropertyName.toDashedForm("foo")).isEqualTo("foo");
-		assertThat(BeanPropertyName.toDashedForm("fooBar")).isEqualTo("foo-bar");
-		assertThat(BeanPropertyName.toDashedForm("foo_bar")).isEqualTo("foo-bar");
-		assertThat(BeanPropertyName.toDashedForm("_foo_bar")).isEqualTo("-foo-bar");
-		assertThat(BeanPropertyName.toDashedForm("foo_Bar")).isEqualTo("foo-bar");
+		assertThat(DataObjectPropertyName.toDashedForm("Foo")).isEqualTo("foo");
+		assertThat(DataObjectPropertyName.toDashedForm("foo")).isEqualTo("foo");
+		assertThat(DataObjectPropertyName.toDashedForm("fooBar")).isEqualTo("foo-bar");
+		assertThat(DataObjectPropertyName.toDashedForm("foo_bar")).isEqualTo("foo-bar");
+		assertThat(DataObjectPropertyName.toDashedForm("_foo_bar")).isEqualTo("-foo-bar");
+		assertThat(DataObjectPropertyName.toDashedForm("foo_Bar")).isEqualTo("foo-bar");
 	}
 
 }

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

@@ -30,11 +30,11 @@ import org.springframework.format.annotation.DateTimeFormat;
 import static org.assertj.core.api.Assertions.assertThat;
 
 /**
- * Tests for {@link ConstructorParametersBinder}.
+ * Tests for {@link ValueObjectBinder}.
  *
  * @author Madhura Bhave
  */
-class ConstructorParametersBinderTests {
+class ValueObjectBinderTests {
 
 	private final List<ConfigurationPropertySource> sources = new ArrayList<>();