Simplify MustacheEnvironmentCollector

Simplify the MustacheEnvironmentCollector so that it no longer binds
the Spring Environment to a Map.

See gh-2242

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mustache/MustacheEnvironmentCollector.java

@@ -21,12 +21,12 @@ import java.util.Map;
 
 import org.springframework.boot.bind.PropertySourcesPropertyValues;
 import org.springframework.boot.bind.RelaxedDataBinder;
+import org.springframework.boot.bind.RelaxedPropertyResolver;
 import org.springframework.context.EnvironmentAware;
 import org.springframework.core.env.ConfigurableEnvironment;
 import org.springframework.core.env.Environment;
 
 import com.samskivert.mustache.DefaultCollector;
-import com.samskivert.mustache.Mustache;
 import com.samskivert.mustache.Mustache.Collector;
 import com.samskivert.mustache.Mustache.VariableFetcher;
 
@@ -43,42 +43,38 @@ public class MustacheEnvironmentCollector extends DefaultCollector implements
 
 	private Map<String, Object> target;
 
+	private RelaxedPropertyResolver propertyResolver;
+
+	private final VariableFetcher propertyFetcher = new PropertyVariableFetcher();
+
 	@Override
 	public void setEnvironment(Environment environment) {
 		this.environment = (ConfigurableEnvironment) environment;
 		this.target = new HashMap<String, Object>();
 		new RelaxedDataBinder(this.target).bind(new PropertySourcesPropertyValues(
 				this.environment.getPropertySources()));
+		this.propertyResolver = new RelaxedPropertyResolver(environment);
 	}
 
 	@Override
-	public Mustache.VariableFetcher createFetcher(Object ctx, String name) {
+	public VariableFetcher createFetcher(Object ctx, String name) {
 		VariableFetcher fetcher = super.createFetcher(ctx, name);
 		if (fetcher != null) {
 			return fetcher;
 		}
-		if (this.environment.containsProperty(name)) {
-			return new VariableFetcher() {
-
-				@Override
-				public Object get(Object ctx, String name) throws Exception {
-					return MustacheEnvironmentCollector.this.environment
-							.getProperty(name);
-				}
-
-			};
-		}
-		if (this.target.containsKey(name)) {
-			return new VariableFetcher() {
-
-				@Override
-				public Object get(Object ctx, String name) throws Exception {
-					return MustacheEnvironmentCollector.this.target.get(name);
-				}
-
-			};
+		if (this.propertyResolver.containsProperty(name)) {
+			return this.propertyFetcher;
 		}
 		return null;
 	}
 
+	private class PropertyVariableFetcher implements VariableFetcher {
+
+		@Override
+		public Object get(Object ctx, String name) throws Exception {
+			return MustacheEnvironmentCollector.this.propertyResolver.getProperty(name);
+		}
+
+	}
+
 }