uri-template implementation

Author: erosb

core/pom.xml

@@ -172,5 +172,10 @@
             <version>1.0.5</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>com.damnhandy</groupId>
+            <artifactId>handy-uri-templates</artifactId>
+            <version>2.1.6</version>
+        </dependency>
     </dependencies>
 </project>

core/src/main/java/org/everit/json/schema/internal/URITemplateFormatValidator.java

@@ -1,13 +1,23 @@
 package org.everit.json.schema.internal;
 
+import static java.lang.String.format;
+
 import java.util.Optional;
 
 import org.everit.json.schema.FormatValidator;
 
+import com.damnhandy.uri.template.MalformedUriTemplateException;
+import com.damnhandy.uri.template.UriTemplate;
+
 public class URITemplateFormatValidator implements FormatValidator {
 
     @Override public Optional<String> validate(String subject) {
-        throw new UnsupportedOperationException("not yet implemented");
+        try {
+            UriTemplate.fromTemplate(subject);
+            return Optional.empty();
+        } catch (MalformedUriTemplateException e) {
+            return Optional.of(format("[%s] is not a valid URI template", subject));
+        }
     }
 
     @Override public String formatName() {