Create RelaxedPropertyResolver

Create RelaxedPropertyResolver class that can be used to get values
from another PropertyResolver (probably an Environment) using the
same relaxed rules as the RelaxedDataBinder.

The commit extracts the relaxed naming rules from RelaxedDataBinder
into a new RelaxedNames class.

Issue: #55621278

Author: Phillip Webb

spring-boot/src/main/java/org/springframework/boot/bind/RelaxedDataBinder.java

@@ -37,6 +37,7 @@
  * case for example).
  * 
  * @author Dave Syer
+ * @see RelaxedNames
  */
 public class RelaxedDataBinder extends DataBinder {
 
@@ -224,76 +225,19 @@ private void extendMapIfNecessary(BeanWrapper wrapper, BeanPath path, int index)
 
 	private String getActualPropertyName(BeanWrapper target, String prefix, String name) {
 		prefix = StringUtils.hasText(prefix) ? prefix + "." : "";
-		for (Variation variation : Variation.values()) {
-			for (Manipulation manipulation : Manipulation.values()) {
-				// Apply all manipulations before attempting variations
-				String candidate = variation.apply(manipulation.apply(name));
-				try {
-					if (target.getPropertyType(prefix + candidate) != null) {
-						return candidate;
-					}
-				}
-				catch (InvalidPropertyException ex) {
-					// swallow and continue
+		for (String candidate : new RelaxedNames(name)) {
+			try {
+				if (target.getPropertyType(prefix + candidate) != null) {
+					return candidate;
 				}
 			}
+			catch (InvalidPropertyException ex) {
+				// swallow and continue
+			}
 		}
 		return name;
 	}
 
-	static enum Variation {
-		NONE {
-			@Override
-			public String apply(String value) {
-				return value;
-			}
-		},
-		UPPERCASE {
-			@Override
-			public String apply(String value) {
-				return value.toUpperCase();
-			}
-		},
-
-		LOWERCASE {
-			@Override
-			public String apply(String value) {
-				return value.toLowerCase();
-			}
-		};
-
-		public abstract String apply(String value);
-	}
-
-	static enum Manipulation {
-		NONE {
-			@Override
-			public String apply(String value) {
-				return value;
-			}
-		},
-		UNDERSCORE {
-			@Override
-			public String apply(String value) {
-				return value.replace("-", "_");
-			}
-		},
-
-		CAMELCASE {
-			@Override
-			public String apply(String value) {
-				StringBuilder builder = new StringBuilder();
-				for (String field : UNDERSCORE.apply(value).split("_")) {
-					builder.append(builder.length() == 0 ? field : StringUtils
-							.capitalize(field));
-				}
-				return builder.toString();
-			}
-		};
-
-		public abstract String apply(String value);
-	}
-
 	static class MapHolder {
 		private Map<String, Object> map;
 

spring-boot/src/main/java/org/springframework/boot/bind/RelaxedNames.java

@@ -0,0 +1,135 @@
+/*
+ * Copyright 2012-2013 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
+ *
+ *      http://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.bind;
+
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+import org.springframework.util.StringUtils;
+
+/**
+ * Generates relaxed name variations from a given source.
+ * 
+ * @author Phillip Webb
+ * @author Dave Syer
+ * @see RelaxedDataBinder
+ * @see RelaxedPropertyResolver
+ */
+public final class RelaxedNames implements Iterable<String> {
+
+	private final String name;
+
+	/**
+	 * Create a new {@link RelaxedNames} instance.
+	 * 
+	 * @param name the source name. For the maximum number of variations specify the name
+	 * using dashed notation (e.g. {@literal my-property-name}
+	 */
+	public RelaxedNames(String name) {
+		this.name = name;
+	}
+
+	@Override
+	public Iterator<String> iterator() {
+		return new RelaxedNamesIterator();
+	}
+
+	private class RelaxedNamesIterator implements Iterator<String> {
+
+		private int variation = 0;
+
+		private int manipulation = 0;
+
+		@Override
+		public boolean hasNext() {
+			return (this.variation < Variation.values().length);
+		}
+
+		@Override
+		public String next() {
+			if (!hasNext()) {
+				throw new NoSuchElementException();
+			}
+			String result = RelaxedNames.this.name;
+			result = Manipulation.values()[this.manipulation].apply(result);
+			result = Variation.values()[this.variation].apply(result);
+			this.manipulation++;
+			if (this.manipulation >= Manipulation.values().length) {
+				this.variation++;
+				this.manipulation = 0;
+			}
+			return result;
+		}
+
+		@Override
+		public void remove() {
+			throw new UnsupportedOperationException();
+		}
+
+	}
+
+	static enum Variation {
+		NONE {
+			@Override
+			public String apply(String value) {
+				return value;
+			}
+		},
+		LOWERCASE {
+			@Override
+			public String apply(String value) {
+				return value.toLowerCase();
+			}
+		},
+		UPPERCASE {
+			@Override
+			public String apply(String value) {
+				return value.toUpperCase();
+			}
+		};
+
+		public abstract String apply(String value);
+	}
+
+	static enum Manipulation {
+		NONE {
+			@Override
+			public String apply(String value) {
+				return value;
+			}
+		},
+		UNDERSCORE {
+			@Override
+			public String apply(String value) {
+				return value.replace("-", "_");
+			}
+		},
+		CAMELCASE {
+			@Override
+			public String apply(String value) {
+				StringBuilder builder = new StringBuilder();
+				for (String field : UNDERSCORE.apply(value).split("_")) {
+					builder.append(builder.length() == 0 ? field : StringUtils
+							.capitalize(field));
+				}
+				return builder.toString();
+			}
+		};
+
+		public abstract String apply(String value);
+	}
+}