Polish documentation on @ConfigurationProperties getters and setters

- Correct typo (coercable -> coercible)
 - Update description to reflect that Spring 4.1.5 supports the
   expansion of array properties and and a test that verifies the
   behaviour

spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -529,19 +529,16 @@ the configuration of your application. For example:
 	}
 ----
 
-NOTE: The getters and setters are advisable, since binding is via
+NOTE: The getters and setters are advisable, since binding is via standard Java Beans
-standard Java Beans property descriptors, just like in Spring
+property descriptors, just like in Spring MVC. They are mandatory for immutable types
-MVC. They are mandatory for immutable types or those that are directly
+or those that are directly coercible from `String`. As long as they are initialized,
-coercable from `String`. As long as they are initialized maps and
+maps, collections, and arrays need a getter but not necessarily a setter since they
-collections need a getter but not necessarily a setter, for instance,
+can be mutated by the binder. If there is a setter, Maps, collections, and arrays can
-since they can be mutated by the binder. Maps and collections can also
+be created. Maps and collections can be expanded with only a getter, whereas arrays
-be created (if there is a setter) and expanded (in any case), but
+require a setter. Nested POJO properties can also be created (so a setter is not
-arrays can not (so normally arrays need to be bound to a
+mandatory) if they have a default constructor, or a constructor accepting a single
-comma-separated value, but lists can be bound to individual
+value that can be coerced from String. Some people use Project Lombok to add getters
-elements). Nested POJO properties can also be created (so a setter is
+and setters automatically.
-not mandatory) if they have a default constructor, or a constructor
-accepting a single value that can be coerced from String. Some people
-use Project Lombok to add getters and setters automatically.
 
 When the `@EnableConfigurationProperties` annotation is applied to your `@Configuration`,
 any beans annotated with `@ConfigurationProperties` will be automatically configured

spring-boot/src/test/java/org/springframework/boot/context/properties/ConfigurationPropertiesBindingPostProcessorTests.java

@@ -216,6 +216,16 @@ public class ConfigurationPropertiesBindingPostProcessorTests {
 				equalTo("word".toCharArray()));
 	}
 
+	@Test
+	public void configurationPropertiesWithArrayExpansion() throws Exception {
+		this.context = new AnnotationConfigApplicationContext();
+		EnvironmentTestUtils.addEnvironment(this.context, "test.chars[4]:s");
+		this.context.register(PropertyWithCharArrayExpansion.class);
+		this.context.refresh();
+		assertThat(this.context.getBean(PropertyWithCharArrayExpansion.class).getChars(),
+				equalTo("words".toCharArray()));
+	}
+
 	@Test
 	public void notWritablePropertyException() throws Exception {
 		this.context = new AnnotationConfigApplicationContext();
@@ -357,6 +367,23 @@ public class ConfigurationPropertiesBindingPostProcessorTests {
 
 	}
 
+	@Configuration
+	@EnableConfigurationProperties
+	@ConfigurationProperties(prefix = "test", ignoreUnknownFields = false)
+	public static class PropertyWithCharArrayExpansion {
+
+		private char[] chars = new char[] { 'w', 'o', 'r', 'd' };
+
+		public char[] getChars() {
+			return this.chars;
+		}
+
+		public void setChars(char[] chars) {
+			this.chars = chars;
+		}
+
+	}
+
 	@Configuration
 	@EnableConfigurationProperties
 	@ConfigurationProperties(prefix = "test")