Trying to resolve null/"" problem

Author: cowtowncoder

src/main/java/com/fasterxml/jackson/dataformat/xml/XmlMapper.java

@@ -76,6 +76,9 @@ public Builder(XmlFactory f) {
 
             // 04-May-2018, tatu: Important! Let's also default `String` `null` handling to coerce
             //   to empty string -- this lets us induce `null` from empty tags first
+
+            // 08-Sep-2019, tatu: Note: this could conflict with [dataformat-xml#354] (true `null`s
+            //    with `xsi:nil`) unless we are careful to distinguish empty/null
             _configOverrides.findOrCreateOverride(String.class)
                 .setNullHandling(JsonSetter.Value.forValueNulls(Nulls.AS_EMPTY));
         }

src/main/java/com/fasterxml/jackson/dataformat/xml/deser/XmlStringDeserializer.java

@@ -6,6 +6,7 @@
 import com.fasterxml.jackson.databind.*;
 import com.fasterxml.jackson.databind.deser.std.StdScalarDeserializer;
 import com.fasterxml.jackson.databind.jsontype.TypeDeserializer;
+import com.fasterxml.jackson.databind.util.AccessPattern;
 
 /**
  * Custom variant used instead of "plain" {@code StringDeserializer} to handle
@@ -22,10 +23,20 @@ public class XmlStringDeserializer
     public boolean isCachable() { return true; }
 
     @Override
-    public Object getEmptyValue(DeserializationContext ctxt) throws JsonMappingException {
+    public Object getEmptyValue(DeserializationContext ctxt) {
         return "";
     }
 
+    @Override
+    public Object getNullValue(DeserializationContext ctxt) {
+        return null;
+    }
+
+    @Override
+    public AccessPattern getEmptyAccessPattern() {
+        return AccessPattern.CONSTANT;
+    }
+
     @Override
     public String deserialize(JsonParser p, DeserializationContext ctxt) throws IOException
     {