tidy up output validation configuration files

CityDoctorParent/CityDoctorValidation/src/main/java/de/hft/stuttgart/citydoctor2/check/ValidationConfiguration.java

@@ -35,6 +35,14 @@ import org.apache.logging.log4j.Logger;
 import org.yaml.snakeyaml.DumperOptions;
 import org.yaml.snakeyaml.Yaml;
 import org.yaml.snakeyaml.constructor.Constructor;
+import org.yaml.snakeyaml.introspector.Property;
+import org.yaml.snakeyaml.nodes.CollectionNode;
+import org.yaml.snakeyaml.nodes.MappingNode;
+import org.yaml.snakeyaml.nodes.Node;
+import org.yaml.snakeyaml.nodes.NodeTuple;
+import org.yaml.snakeyaml.nodes.SequenceNode;
+import org.yaml.snakeyaml.nodes.Tag;
+import org.yaml.snakeyaml.representer.Representer;
 
 import de.hft.stuttgart.citydoctor2.checks.CheckPrototype;
 import de.hft.stuttgart.citydoctor2.checks.Checks;
@@ -97,7 +105,41 @@ public class ValidationConfiguration implements Serializable {
 	public void saveAs(File f) throws IOException {
 		DumperOptions options = new DumperOptions();
 		options.setDefaultFlowStyle(DumperOptions.FlowStyle.BLOCK);
-		Yaml yaml = new Yaml(options);
+		options.setPrettyFlow(true);
+		Representer rep = new Representer() {
+
+			@Override
+			protected NodeTuple representJavaBeanProperty(Object javaBean, Property property, Object propertyValue,
+					Tag customTag) {
+	            if (propertyValue == null) {
+	                return null;
+	            } else {
+		            NodeTuple tuple = super.representJavaBeanProperty(javaBean, property, propertyValue,
+		                    customTag);
+		            Node valueNode = tuple.getValueNode();
+		            if (Tag.NULL.equals(valueNode.getTag())) {
+		                return null;// skip 'null' values
+		            }
+		            if (valueNode instanceof CollectionNode) {
+		                if (Tag.SEQ.equals(valueNode.getTag())) {
+		                    SequenceNode seq = (SequenceNode) valueNode;
+		                    if (seq.getValue().isEmpty()) {
+		                        return null;// skip empty lists
+		                    }
+		                }
+		                if (Tag.MAP.equals(valueNode.getTag())) {
+		                    MappingNode seq = (MappingNode) valueNode;
+		                    if (seq.getValue().isEmpty()) {
+		                        return null;// skip empty maps
+		                    }
+		                }
+		            }
+		            return tuple;
+	            }
+			}
+		};
+		rep.addClassTag(ValidationConfiguration.class, Tag.MAP);
+		Yaml yaml = new Yaml(rep, options);
 		try (BufferedWriter bw = new BufferedWriter(new FileWriter(f))) {
 			yaml.dump(this, bw);
 		}
@@ -202,8 +244,8 @@ public class ValidationConfiguration implements Serializable {
 		}
 		return parserConfig;
 	}
-	
-	public void setParserConfiguration(ParserConfiguration parserConfig) {
+
+	public void setParserConfig(ParserConfiguration parserConfig) {
 		this.parserConfig = parserConfig;
 	}