Fix #561: Deserializing empty timestamp fields to null value doesn't work (#825)

Author: cowtowncoder

release-notes/VERSION

@@ -51,6 +51,10 @@ Version: 3.x (for earlier see VERSION-2.x)
   polymorphic nested objects
  (reported by Vitor P)
  (fix by @cowtowncoder, w/ Claude code)
+#561: Deserializing empty timestamp fields to `null` value doesn't
+  work (instead becomes "empty", Epoch time)
+ (reported by @silvestr85)
+ (fix by @cowtowncoder, w/ Claude code)
 #565: Blank text is ignored in `@JacksonXmlText`
  (reported by Alessandro A)
  (fix by @cowtowncoder, w/ Claude code)

src/main/java/tools/jackson/dataformat/xml/XmlMapper.java

@@ -107,6 +107,9 @@ public Builder(XmlFactory f) {
                 .setCoercion(CoercionInputShape.EmptyString, CoercionAction.AsNull);
             _coercionConfigs.findOrCreateCoercion(LogicalType.Boolean)
                 .setCoercion(CoercionInputShape.EmptyString, CoercionAction.AsNull);
+            // 18-Mar-2026, tatu: [dataformat-xml#561] Same for Date/Time types
+            _coercionConfigs.findOrCreateCoercion(LogicalType.DateTime)
+                .setCoercion(CoercionInputShape.EmptyString, CoercionAction.AsNull);
         }
 
         @Override

src/test/java/tools/jackson/dataformat/xml/deser/EmptyTimestampDeser561Test.java

@@ -0,0 +1,69 @@
+package tools.jackson.dataformat.xml.deser;
+
+import java.util.Date;
+
+import org.junit.jupiter.api.Test;
+
+import com.fasterxml.jackson.annotation.JsonFormat;
+
+import tools.jackson.dataformat.xml.XmlMapper;
+import tools.jackson.dataformat.xml.XmlTestUtil;
+import tools.jackson.dataformat.xml.annotation.JacksonXmlProperty;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+// [dataformat-xml#561] Empty timestamp/date attribute should deserialize as null
+public class EmptyTimestampDeser561Test extends XmlTestUtil
+{
+    static class DateAttrBean {
+        @JacksonXmlProperty(isAttribute = true)
+        @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss")
+        public Date timestampDate;
+    }
+
+    static class DateElementBean {
+        @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss")
+        public Date timestampDate;
+    }
+
+    static class DateBean {
+        @JacksonXmlProperty(isAttribute = true)
+        @JsonFormat(pattern = "yyyy-MM-dd")
+        public Date dateValue;
+    }
+
+    private final XmlMapper MAPPER = newMapper();
+
+    // [dataformat-xml#561]: empty attribute
+    @Test
+    public void testEmptyDateAttributeWithTimestampFormat() throws Exception
+    {
+        DateAttrBean result = MAPPER.readValue(
+                "<DateAttrBean timestampDate=\"\" />",
+                DateAttrBean.class);
+        assertNotNull(result);
+        assertNull(result.timestampDate);
+    }
+
+    // [dataformat-xml#561]: empty element
+    @Test
+    public void testEmptyDateElement() throws Exception
+    {
+        DateElementBean result = MAPPER.readValue(
+                "<DateElementBean><timestampDate></timestampDate></DateElementBean>",
+                DateElementBean.class);
+        assertNotNull(result);
+        assertNull(result.timestampDate);
+    }
+
+    // [dataformat-xml#561]: empty Date attribute
+    @Test
+    public void testEmptyDateAttribute() throws Exception
+    {
+        DateBean result = MAPPER.readValue(
+                "<DateBean dateValue=\"\" />",
+                DateBean.class);
+        assertNotNull(result);
+        assertNull(result.dateValue);
+    }
+}