Make Map<String,String> a special case in RelaxedDataBinder

Fixes gh-195

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

@@ -187,6 +187,14 @@ public class RelaxedDataBinder extends DataBinder {
 		if (descriptor == null || descriptor.isMap()) {
 			if (descriptor != null) {
 				wrapper.getPropertyValue(name + "[foo]");
+				TypeDescriptor valueDescriptor = descriptor.getMapValueTypeDescriptor();
+				if (valueDescriptor != null) {
+					Class<?> valueType = valueDescriptor.getObjectType();
+					if (valueType != null
+							&& CharSequence.class.isAssignableFrom(valueType)) {
+						path.collapseKeys(index);
+					}
+				}
 			}
 			path.mapIndex(index);
 			extendMapIfNecessary(wrapper, path, index);
@@ -278,6 +286,22 @@ public class RelaxedDataBinder extends DataBinder {
 			this.nodes = splitPath(path);
 		}
 
+		public void collapseKeys(int index) {
+			List<PathNode> revised = new ArrayList<PathNode>();
+			for (int i = 0; i < index; i++) {
+				revised.add(this.nodes.get(i));
+			}
+			StringBuilder builder = new StringBuilder();
+			for (int i = index; i < this.nodes.size(); i++) {
+				if (i > index) {
+					builder.append(".");
+				}
+				builder.append(this.nodes.get(i).name);
+			}
+			revised.add(new PropertyNode(builder.toString()));
+			this.nodes = revised;
+		}
+
 		public void mapIndex(int index) {
 			PathNode node = this.nodes.get(index);
 			if (node instanceof PropertyNode) {

spring-boot/src/test/java/org/springframework/boot/bind/RelaxedDataBinderTests.java

@@ -250,6 +250,14 @@ public class RelaxedDataBinderTests {
 		assertEquals("123", target.getNested().get("value"));
 	}
 
+	@Test
+	public void testBindNestedMapOfString() throws Exception {
+		TargetWithNestedMapOfString target = new TargetWithNestedMapOfString();
+		bind(target, "nested.foo: bar\n" + "nested.value.foo: 123");
+		assertEquals("bar", target.getNested().get("foo"));
+		assertEquals("123", target.getNested().get("value.foo"));
+	}
+
 	@Test
 	public void testBindNestedMapBracketReferenced() throws Exception {
 		TargetWithNestedMap target = new TargetWithNestedMap();
@@ -469,6 +477,18 @@ public class RelaxedDataBinderTests {
 		}
 	}
 
+	public static class TargetWithNestedMapOfString {
+		private Map<String, String> nested;
+
+		public Map<String, String> getNested() {
+			return this.nested;
+		}
+
+		public void setNested(Map<String, String> nested) {
+			this.nested = nested;
+		}
+	}
+
 	public static class TargetWithNestedMapOfListOfString {
 		private Map<String, List<String>> nested;
 

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

@@ -26,7 +26,6 @@ import javax.validation.constraints.NotNull;
 
 import org.hamcrest.Matchers;
 import org.junit.After;
-import org.junit.Ignore;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
@@ -326,7 +325,6 @@ public class EnableConfigurationPropertiesTests {
 	}
 
 	@Test
-	@Ignore("This is challenging, so maybe not supportable?")
 	public void testBindingWithMapKeyWithPeriod() {
 		this.context.register(ResourceBindingPropertiesWithMap.class);
 		this.context.refresh();