Added suppressing adapters to leave default values out of XML

src/main/java/de/rub/nds/modifiablevariable/util/SuppressingBooleanAdapter.java

@@ -0,0 +1,33 @@
+/*
+ * ModifiableVariable - A Variable Concept for Runtime Modifications
+ *
+ * Ruhr University Bochum, Paderborn University, Technology Innovation Institute, and Hackmanit GmbH
+ *
+ * Licensed under Apache License 2.0 http://www.apache.org/licenses/LICENSE-2.0
+ */
+package de.rub.nds.modifiablevariable.util;
+
+import jakarta.xml.bind.annotation.adapters.XmlAdapter;
+import java.util.Objects;
+
+public abstract class SuppressingBooleanAdapter extends XmlAdapter<String, Boolean> {
+
+    public abstract Boolean getValueToSuppress();
+
+    @Override
+    public Boolean unmarshal(String v) throws Exception {
+        if (v == null) {
+            return getValueToSuppress();
+        } else {
+            return Boolean.parseBoolean(v);
+        }
+    }
+
+    @Override
+    public String marshal(Boolean v) throws Exception {
+        if (Objects.equals(v, getValueToSuppress()) || v == null) {
+            return null;
+        }
+        return v.toString();
+    }
+}

src/main/java/de/rub/nds/modifiablevariable/util/SuppressingFalseBooleanAdapter.java

@@ -0,0 +1,16 @@
+/*
+ * ModifiableVariable - A Variable Concept for Runtime Modifications
+ *
+ * Ruhr University Bochum, Paderborn University, Technology Innovation Institute, and Hackmanit GmbH
+ *
+ * Licensed under Apache License 2.0 http://www.apache.org/licenses/LICENSE-2.0
+ */
+package de.rub.nds.modifiablevariable.util;
+
+public class SuppressingFalseBooleanAdapter extends SuppressingBooleanAdapter {
+
+    @Override
+    public Boolean getValueToSuppress() {
+        return Boolean.FALSE;
+    }
+}

src/main/java/de/rub/nds/modifiablevariable/util/SuppressingTrueBooleanAdapter.java

@@ -0,0 +1,15 @@
+/*
+ * ModifiableVariable - A Variable Concept for Runtime Modifications
+ *
+ * Ruhr University Bochum, Paderborn University, Technology Innovation Institute, and Hackmanit GmbH
+ *
+ * Licensed under Apache License 2.0 http://www.apache.org/licenses/LICENSE-2.0
+ */
+package de.rub.nds.modifiablevariable.util;
+
+public class SuppressingTrueBooleanAdapter extends SuppressingBooleanAdapter {
+    @Override
+    public Boolean getValueToSuppress() {
+        return Boolean.TRUE;
+    }
+}