Fixes #634: add deserialization support for xsi:type auto-detection (#635)

Author: cowtowncoder

release-notes/VERSION-2.x

@@ -14,6 +14,8 @@ Project: jackson-dataformat-xml
  (reported by Arthur C)
 #631: Add `XmlMapper.createGenerator(XMLStreamWriter)` and
   `XmlMapper.createParser(XMLStreamReader)` overloads
+#634: Support use of xsi:type for polymorphic deserialization
+  (FromXmlParser.Feature.AUTO_DETECT_XSI_TYPE)
 * Upgrade Woodstox to 6.6.0 (latest at the time)
 
 2.16.1 (24-Dec-2023)

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

@@ -7,6 +7,7 @@
 import java.math.BigInteger;
 import java.util.Set;
 
+import javax.xml.XMLConstants;
 import javax.xml.stream.XMLStreamException;
 import javax.xml.stream.XMLStreamReader;
 import javax.xml.stream.XMLStreamWriter;
@@ -57,6 +58,20 @@ public class FromXmlParser
      */
     public enum Feature implements FormatFeature
     {
+        /**
+         * Feature that enables automatic conversion of incoming "xsi:type"
+         * (where "type"  is the local name and "xsi" prefix is bound to URI
+         * {@link XMLConstants#W3C_XML_SCHEMA_INSTANCE_NS_URI}),
+         * into Jackson simple Property Name of {@code "xsi:type"}.
+         * This is usually needed to read content written using
+         * matching {@code ToXmlGenerator.Feature#AUTO_DETECT_XSI_TYPE} feature,
+         * usually used for Polymorphic handling where it is difficult
+         * to specify proper XML Namespace for type identifier.
+         *
+         * @since 2.17
+         */
+        AUTO_DETECT_XSI_TYPE(false),
+
         /**
          * Feature that indicates whether XML Empty elements (ones where there are
          * no separate start and end tags, but just one tag that ends with "/>")

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

@@ -75,6 +75,9 @@ public class XmlTokenStream
 
     protected boolean _cfgProcessXsiNil;
 
+    // @since 2.17
+    protected boolean _cfgProcessXsiType;
+
     protected XmlNameProcessor _nameProcessor;
 
     /*
@@ -169,6 +172,7 @@ public XmlTokenStream(XMLStreamReader xmlReader, ContentReference sourceRef,
         _sourceReference = sourceRef;
         _formatFeatures = formatFeatures;
         _cfgProcessXsiNil = FromXmlParser.Feature.PROCESS_XSI_NIL.enabledIn(_formatFeatures);
+        _cfgProcessXsiType = FromXmlParser.Feature.AUTO_DETECT_XSI_TYPE.enabledIn(_formatFeatures);
         // 04-Dec-2023, tatu: [dataformat-xml#618] Need further customized adapter:
         _xmlReader = Stax2JacksonReaderAdapter.wrapIfNecessary(xmlReader);
         _nameProcessor = nameProcessor;
@@ -247,6 +251,7 @@ public XMLStreamReader2 getXmlReader() {
     protected void setFormatFeatures(int f) {
         _formatFeatures = f;
         _cfgProcessXsiNil = FromXmlParser.Feature.PROCESS_XSI_NIL.enabledIn(f);
+        _cfgProcessXsiType = FromXmlParser.Feature.AUTO_DETECT_XSI_TYPE.enabledIn(f);
     }
 
     /*
@@ -517,7 +522,6 @@ private final int _next() throws XMLStreamException
             return (_currentState = XML_END);
         case XML_END:
             return XML_END;
-//            throw new IllegalStateException("No more XML tokens available (end of input)");
         }
         // Ok: must be END_ELEMENT; see what tag we get (or end)
         switch (_skipAndCollectTextUntilTag()) {
@@ -712,6 +716,15 @@ private final void _checkXsiAttributes() {
      * @since 2.14
      */
     protected void _decodeElementName(String namespaceURI, String localName) {
+        // 31-Jan-2024, tatu: [dataformat-xml#634] Need to convert 'xsi:type'?
+        //    (not 100% sure if needed for elements but let's do for now)
+        if (_cfgProcessXsiType) {
+            if (localName.equals("type") && XSI_NAMESPACE.equals(namespaceURI)) {
+                _localName = "xsi:type";
+                _namespaceURI = ""; // or could leave as it was?
+                return;
+            }
+        }
         _nameToDecode.namespace = namespaceURI;
         _nameToDecode.localPart = localName;
         _nameProcessor.decodeName(_nameToDecode);
@@ -723,6 +736,14 @@ protected void _decodeElementName(String namespaceURI, String localName) {
      * @since 2.14
      */
     protected void _decodeAttributeName(String namespaceURI, String localName) {
+        // 31-Jan-2024, tatu: [dataformat-xml#634] Need to convert 'xsi:type'?
+        if (_cfgProcessXsiType) {
+            if (localName.equals("type") && XSI_NAMESPACE.equals(namespaceURI)) {
+                _localName = "xsi:type";
+                _namespaceURI = ""; // or could leave as it was?
+                return;
+            }
+        }
         _nameToDecode.namespace = namespaceURI;
         _nameToDecode.localPart = localName;
         _nameProcessor.decodeName(_nameToDecode);

src/test/java/com/fasterxml/jackson/dataformat/xml/deser/XsiTypeReadTest.java

@@ -0,0 +1,53 @@
+package com.fasterxml.jackson.dataformat.xml.deser;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonRootName;
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import com.fasterxml.jackson.annotation.JsonTypeInfo.As;
+import com.fasterxml.jackson.annotation.JsonTypeInfo.Id;
+import com.fasterxml.jackson.dataformat.xml.XmlMapper;
+import com.fasterxml.jackson.dataformat.xml.XmlTestBase;
+import com.fasterxml.jackson.dataformat.xml.ser.ToXmlGenerator;
+
+// [dataformat-xml#634]
+public class XsiTypeReadTest extends XmlTestBase
+{
+    @JsonRootName("Typed")
+    static class TypeBean {
+        @JsonProperty("xsi:type")
+        public String typeId;
+
+        protected TypeBean() { }
+        public TypeBean(String typeId) {
+            this.typeId = typeId;
+        }
+    }
+
+    @JsonRootName("Poly")
+    @JsonTypeInfo(use = Id.SIMPLE_NAME, include = As.PROPERTY, property="xsi:type")
+    static class PolyBean {
+        public int value;
+
+        protected PolyBean() { }
+        public PolyBean(int v) { value = v; }
+    }
+
+    private final XmlMapper XSI_ENABLED_MAPPER = XmlMapper.builder()
+            .configure(ToXmlGenerator.Feature.AUTO_DETECT_XSI_TYPE, true)
+            .configure(FromXmlParser.Feature.AUTO_DETECT_XSI_TYPE, true)
+            .build();
+
+    public void testExplicitXsiTypeReadEnabled() throws Exception
+    {
+        final String XML = XSI_ENABLED_MAPPER.writeValueAsString(new TypeBean("type0"));
+        TypeBean result = XSI_ENABLED_MAPPER.readValue(XML, TypeBean.class);
+        assertEquals("type0", result.typeId);
+    }
+
+    public void testXsiTypeAsTypeReadeEnabled() throws Exception
+    {
+        final String XML = XSI_ENABLED_MAPPER.writeValueAsString(new PolyBean(42));
+        PolyBean result = XSI_ENABLED_MAPPER.readValue(XML, PolyBean.class);
+        assertEquals(42, result.value);
+    }
+}