Fix AASSimple in XML-Dataformat

- unifies XML-AASSimple with JSON
- XML-Mapper uses NON_NULL by default instead of NON_EMPTY
- AnnotationIntrospector for XML-Mapper adds NON_EMPTY to collections

Author: Daespen

dataformat-xml/src/main/java/io/adminshell/aas/v3/dataformat/xml/XmlDataformatAnnotationIntrospector.java

@@ -15,18 +15,28 @@
  */
 package io.adminshell.aas.v3.dataformat.xml;
 
+import java.util.Collection;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.databind.introspect.Annotated;
 import com.fasterxml.jackson.databind.introspect.AnnotatedClass;
+import com.fasterxml.jackson.databind.introspect.AnnotatedMethod;
 import com.fasterxml.jackson.dataformat.xml.JacksonXmlAnnotationIntrospector;
 
+import io.adminshell.aas.v3.dataformat.core.ReflectionHelper;
+
 /**
  * This class helps to dynamically decide how to de-/serialize classes and
  * properties defined in the AAS model library. It will automatically add a default namespace
  * to property names and set a default property order for contained elements.
+ * 
+ * Will also add @JsonInclude(JsonInclude.Include.NON_EMPTY) to all getter methods returning any type of
+ * Collection<?> defined in the AAS model
  */
 public class XmlDataformatAnnotationIntrospector extends JacksonXmlAnnotationIntrospector {
     private static final long serialVersionUID = 1L;
 
+    private static final String GETTER_PREFIX = "get";
     protected String myDefaultNamespace = "";
 
     public XmlDataformatAnnotationIntrospector() {
@@ -57,4 +67,22 @@ public String[] findSerializationPropertyOrder(AnnotatedClass ac) {
         }
         return order;
     }
-}
+
+    @Override
+    public JsonInclude.Value findPropertyInclusion(Annotated a) {
+        JsonInclude.Value result = super.findPropertyInclusion(a);
+        if (result != JsonInclude.Value.empty()) {
+            return result;
+        }
+        if (AnnotatedMethod.class.isAssignableFrom(a.getClass())) {
+            AnnotatedMethod method = (AnnotatedMethod) a;
+            if (method.getParameterCount() == 0
+                    && method.getName().startsWith(GETTER_PREFIX)
+                    && Collection.class.isAssignableFrom(method.getRawReturnType())
+                    && ReflectionHelper.isModelInterfaceOrDefaultImplementation(method.getDeclaringClass())) {
+                return result.withValueInclusion(JsonInclude.Include.NON_EMPTY);
+            }
+        }
+        return result;
+    }
+}

dataformat-xml/src/main/java/io/adminshell/aas/v3/dataformat/xml/XmlSerializer.java

@@ -58,7 +58,7 @@ protected void buildMapper() {
         mapper = XmlMapper.builder()
                 .enable(SerializationFeature.INDENT_OUTPUT)
                 .enable(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY)
-                .serializationInclusion(JsonInclude.Include.NON_EMPTY)
+                .serializationInclusion(JsonInclude.Include.NON_NULL)
                 .annotationIntrospector(new XmlDataformatAnnotationIntrospector())
                 .defaultUseWrapper(false)
                 .addModule(buildEnumModule())

dataformat-xml/src/main/java/io/adminshell/aas/v3/dataformat/xml/serialization/LangStringsSerializer.java

@@ -18,8 +18,4 @@
 import io.adminshell.aas.v3.model.LangString;
 
 public class LangStringsSerializer extends NoEntryWrapperListSerializer<LangString> {
-    public LangStringsSerializer() {
-        super();
-        this.setObjectForMinCardinality(new LangString());
-    }
 }

dataformat-xml/src/main/java/io/adminshell/aas/v3/dataformat/xml/serialization/NoEntryWrapperListSerializer.java

@@ -29,7 +29,6 @@
  * @param <T> serialized class within the list
  */
 public class NoEntryWrapperListSerializer<T extends Object> extends JsonSerializer<List<T>> {
-    protected T placeholderEntry;
     private String outerWrapperName;
 
     /**
@@ -41,19 +40,9 @@ public void setOuterWrapper(String outerWrapper) {
         this.outerWrapperName = outerWrapper;
     }
 
-    /**
-     * Sets an empty object that is used for serialized lists with minimum cardinality of 1
-     * 
-     * @param emptyOject The placeholder in case the list is empty, but needs to have a size of 1.
-     */
-    public void setObjectForMinCardinality(T emptyOject) {
-        this.placeholderEntry = emptyOject;
-    }
-
     @Override
     public void serialize(List<T> list, JsonGenerator gen, SerializerProvider serializers)
-        throws IOException {
-        addOptionalPlaceholder(list);
+            throws IOException {
         writeList(list, (ToXmlGenerator) gen);
     }
 
@@ -85,14 +74,8 @@ private void writeOuterWrapperEnd(ToXmlGenerator xgen) throws IOException {
         }
     }
 
-    private void addOptionalPlaceholder(List<T> list) {
-        if (list.isEmpty() && placeholderEntry != null) {
-            list.add(placeholderEntry);
-        }
-    }
-
     @Override
     public boolean isEmpty(SerializerProvider provider, List<T> value) {
         return value == null || value.isEmpty();
     }
-}
+}