Improve property target name

Previously, non camel case properties were wrongly resolved, i.e.
getFOO() leading to a 'f-o-o'. While unusual, underscores can also be
added to a property name. In that case, the hyphen should not be added
as the binder consider this to be a single "word". Typically setFoo_Bar
on the "something" prefix is mapped using "something.foo_bar".

All these cases are now handled properly, generating the target name that
the binder expects.

Fixes gh-2118

spring-boot-tools/spring-boot-configuration-processor/src/main/java/org/springframework/boot/configurationprocessor/metadata/ConfigurationMetadata.java

@@ -19,6 +19,8 @@ package org.springframework.boot.configurationprocessor.metadata;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 /**
  * Configuration meta-data.
@@ -30,6 +32,8 @@ import java.util.List;
  */
 public class ConfigurationMetadata {
 
+	private static final Pattern CAMEL_CASE_PATTERN = Pattern.compile("([^A-Z-])([A-Z])");
+
 	private final List<ItemMetadata> items;
 
 	public ConfigurationMetadata() {
@@ -73,15 +77,22 @@ public class ConfigurationMetadata {
 	}
 
 	static String toDashedCase(String name) {
-		StringBuilder dashed = new StringBuilder();
-		for (int i = 0; i < name.length(); i++) {
-			char c = name.charAt(i);
-			if (Character.isUpperCase(c) && dashed.length() > 0) {
-				dashed.append("-");
+		Matcher matcher = CAMEL_CASE_PATTERN.matcher(name);
+		StringBuffer result = new StringBuffer();
+		while (matcher.find()) {
+			String first = matcher.group(1);
+			String second = matcher.group(2);
+			String target;
+			if (first.equals("_")) { // not a word for the binder
+				target = first + second;
+			} else {
+				target = first + "-" + second;
 			}
-			dashed.append(Character.toLowerCase(c));
+			matcher.appendReplacement(result,target);
 		}
-		return dashed.toString();
+		matcher.appendTail(result);
+		String value = result.toString();
+		return value.toLowerCase();
 	}
 
 }

spring-boot-tools/spring-boot-configuration-processor/src/test/java/org/springframework/boot/configurationprocessor/metadata/ConfigurationMetadataTests.java

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2012-2014 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.configurationprocessor.metadata;
+
+import org.junit.Test;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+/**
+ * Tests for {@link ConfigurationMetadata}.
+ *
+ * @author Stephane Nicoll
+ */
+public class ConfigurationMetadataTests {
+
+	@Test
+	public void toDashedCaseCamelCase() {
+		assertThat(ConfigurationMetadata.toDashedCase("simpleCamelCase"), is("simple-camel-case"));
+	}
+
+	@Test
+	public void toDashedCaseWordsUnderScore() {
+		assertThat(ConfigurationMetadata.toDashedCase("Word_With_underscore"), is("word_with_underscore"));
+	}
+
+	@Test
+	public void toDashedCaseWordsSeveralUnderScores() {
+		assertThat(ConfigurationMetadata.toDashedCase("Word___With__underscore"), is("word___with__underscore"));
+	}
+
+	@Test
+	public void toDashedCaseLowerCaseUnderscore() {
+		assertThat(ConfigurationMetadata.toDashedCase("lower_underscore"), is("lower_underscore"));
+	}
+
+	@Test
+	public void toDashedCaseUpperUnderscore() {
+		assertThat(ConfigurationMetadata.toDashedCase("UPPER_UNDERSCORE"), is("upper_underscore"));
+	}
+
+	@Test
+	public void toDashedCaseMultipleUnderscores() {
+		assertThat(ConfigurationMetadata.toDashedCase("super___crazy"), is("super___crazy"));
+	}
+
+	@Test
+	public void toDashedCaseUppercase() {
+		assertThat(ConfigurationMetadata.toDashedCase("UPPERCASE"), is("uppercase"));
+	}
+
+	@Test
+	public void toDashedCaseLowercase() {
+		assertThat(ConfigurationMetadata.toDashedCase("lowercase"), is("lowercase"));
+	}
+
+}