Fix #643: Add ToXmlGenerator.Feature or allowing XML Schema/JAXB compatible Infinity representation (#644)

Author: ahcodedthat

release-notes/CREDITS-2.x

@@ -249,3 +249,9 @@ Arthur Chan (@arthurscchan)
 * Reported, contributed fix for #618: `ArrayIndexOutOfBoundsException` thrown for invalid
   ending XML string when using JDK default Stax XML parser
  (2.17.0)
+
+Alex H (@ahcodedthat)
+
+* Contribtued #643: XML serialization of floating-point infinity is incompatible
+  with JAXB and XML Schema
+ (2.17.0)

release-notes/VERSION-2.x

@@ -18,6 +18,9 @@ Project: jackson-dataformat-xml
   (FromXmlParser.Feature.AUTO_DETECT_XSI_TYPE)
 #637: `JacksonXmlAnnotationIntrospector.findNamespace()` should
   properly merge namespace information
+#643: XML serialization of floating-point infinity is incompatible
+  with JAXB and XML Schema
+ (contributed by Alex H)
 * Upgrade Woodstox to 6.6.1 (latest at the time)
 
 2.16.2 (09-Mar-2024)

src/main/java/com/fasterxml/jackson/dataformat/xml/ser/ToXmlGenerator.java

@@ -106,6 +106,37 @@ public enum Feature implements FormatFeature
          * @since 2.17
          */
         AUTO_DETECT_XSI_TYPE(false),
+
+        /**
+         * Feature that determines how floating-point infinity values are
+         * serialized.
+         *<p>
+         * By default, {@link Float#POSITIVE_INFINITY} and
+         * {@link Double#POSITIVE_INFINITY} are serialized as {@code Infinity},
+         * and {@link Float#NEGATIVE_INFINITY} and
+         * {@link Double#NEGATIVE_INFINITY} are serialized as
+         * {@code -Infinity}. This is the representation that Java normally
+         * uses for these values (see {@link Float#toString(float)} and
+         * {@link Double#toString(double)}), but JAXB and other XML
+         * Schema-conforming readers won't understand it.
+         *<p>
+         * With this feature enabled, these values are instead serialized as
+         * {@code INF} and {@code -INF}, respectively. This is the
+         * representation that XML Schema and JAXB use (see the XML Schema
+         * primitive types
+         * <a href="https://www.w3.org/TR/xmlschema-2/#float"><code>float</code></a>
+         * and
+         * <a href="https://www.w3.org/TR/xmlschema-2/#double"><code>double</code></a>).
+         *<p>
+         * When deserializing, Jackson always understands both representations,
+         * so there is no corresponding
+         * {@link com.fasterxml.jackson.dataformat.xml.deser.FromXmlParser.Feature}.
+         *<p>
+         * Feature is disabled by default for backwards compatibility.
+         *
+         * @since 2.17
+         */
+        WRITE_XML_SCHEMA_CONFORMING_FLOATS(false),
         ;
 
         final boolean _defaultState;
@@ -1174,6 +1205,11 @@ public void writeNumber(long l) throws IOException
     @Override
     public void writeNumber(double d) throws IOException
     {
+        if (Double.isInfinite(d) && isEnabled(Feature.WRITE_XML_SCHEMA_CONFORMING_FLOATS)) {
+            writeNumber(d > 0d ? "INF" : "-INF");
+            return;
+        }
+
         _verifyValueWrite("write number");
         if (_nextName == null) {
             handleMissingName();
@@ -1202,6 +1238,11 @@ public void writeNumber(double d) throws IOException
     @Override
     public void writeNumber(float f) throws IOException
     {
+        if (Float.isInfinite(f) && isEnabled(Feature.WRITE_XML_SCHEMA_CONFORMING_FLOATS)) {
+            writeNumber(f > 0f ? "INF" : "-INF");
+            return;
+        }
+
         _verifyValueWrite("write number");
         if (_nextName == null) {
             handleMissingName();

src/test/java/com/fasterxml/jackson/dataformat/xml/ser/TestSerialization.java

@@ -1,9 +1,9 @@
 package com.fasterxml.jackson.dataformat.xml.ser;
 
-import java.io.*;
 import java.util.*;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
+
 import com.fasterxml.jackson.dataformat.xml.XmlMapper;
 import com.fasterxml.jackson.dataformat.xml.XmlTestBase;
 import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlCData;
@@ -31,6 +31,22 @@ static class AttrAndElem
         public int attr = 42;
     }
 
+    static class Floats
+    {
+        public float elem;
+
+        @JacksonXmlProperty(isAttribute=true, localName="attr")
+        public float attr;
+    }
+
+    static class Doubles
+    {
+        public double elem;
+
+        @JacksonXmlProperty(isAttribute=true, localName="attr")
+        public double attr;
+    }
+
     static class WrapperBean<T>
     {
         public T value;
@@ -81,37 +97,37 @@ static class CustomMap extends LinkedHashMap<String, Integer> { }
 
     private final XmlMapper _xmlMapper = new XmlMapper();
 
-    public void testSimpleAttribute() throws IOException
+    public void testSimpleAttribute() throws Exception
     {
         String xml = _xmlMapper.writeValueAsString(new AttributeBean());
         xml = removeSjsxpNamespace(xml);
         assertEquals("<AttributeBean attr=\"something\"/>", xml);
     }
 
-    public void testSimpleNsElem() throws IOException
+    public void testSimpleNsElem() throws Exception
     {
         String xml = _xmlMapper.writeValueAsString(new NsElemBean());
         xml = removeSjsxpNamespace(xml);
         // here we assume woodstox automatic prefixes, not very robust but:
         assertEquals("<NsElemBean><wstxns1:text xmlns:wstxns1=\"http://foo\">blah</wstxns1:text></NsElemBean>", xml);
     }
 
-    public void testSimpleNsElemWithJsonProp() throws IOException
+    public void testSimpleNsElemWithJsonProp() throws Exception
     {
         String xml = _xmlMapper.writeValueAsString(new NsElemBean2());
         xml = removeSjsxpNamespace(xml);
         // here we assume woodstox automatic prefixes, not very robust but:
         assertEquals("<NsElemBean2><wstxns1:text xmlns:wstxns1=\"http://foo\">blah</wstxns1:text></NsElemBean2>", xml);
     }
 
-    public void testSimpleAttrAndElem() throws IOException
+    public void testSimpleAttrAndElem() throws Exception
     {
         String xml = _xmlMapper.writeValueAsString(new AttrAndElem());
         xml = removeSjsxpNamespace(xml);
         assertEquals("<AttrAndElem id=\"42\"><elem>whatever</elem></AttrAndElem>", xml);
     }
 
-    public void testMap() throws IOException
+    public void testMap() throws Exception
     {
         // First, map in a general wrapper
         LinkedHashMap<String,Integer> map = new LinkedHashMap<String,Integer>();
@@ -136,7 +152,7 @@ public void testMap() throws IOException
                 xml);
     }
 
-    public void testNakedMap() throws IOException
+    public void testNakedMap() throws Exception
     {
         CustomMap input = new CustomMap();        
         input.put("a", 123);
@@ -152,14 +168,14 @@ public void testNakedMap() throws IOException
         assertEquals(Integer.valueOf(456), result.get("b"));
     }
 
-    public void testCDataString() throws IOException
+    public void testCDataString() throws Exception
     {
         String xml = _xmlMapper.writeValueAsString(new CDataStringBean());
         xml = removeSjsxpNamespace(xml);
         assertEquals("<CDataStringBean><value><![CDATA[<some<data\"]]></value></CDataStringBean>", xml);
     }
 
-    public void testCDataStringArray() throws IOException
+    public void testCDataStringArray() throws Exception
     {
         String xml = _xmlMapper.writeValueAsString(new CDataStringArrayBean());
         xml = removeSjsxpNamespace(xml);
@@ -175,4 +191,62 @@ public void testJAXB() throws Exception
         System.out.println("JAXB -> "+sw);
     }
     */
+
+    public void testFloatInfinity() throws Exception
+    {
+        Floats infinite = new Floats();
+        infinite.attr = Float.POSITIVE_INFINITY;
+        infinite.elem = Float.NEGATIVE_INFINITY;
+
+        Floats finite = new Floats();
+        finite.attr = 42.5f;
+        finite.elem = 1337.875f;
+
+        checkFloatInfinity(infinite, false, "<Floats attr=\"Infinity\"><elem>-Infinity</elem></Floats>");
+        checkFloatInfinity(finite, false, "<Floats attr=\"42.5\"><elem>1337.875</elem></Floats>");
+        checkFloatInfinity(infinite, true, "<Floats attr=\"INF\"><elem>-INF</elem></Floats>");
+        checkFloatInfinity(finite, true, "<Floats attr=\"42.5\"><elem>1337.875</elem></Floats>");
+    }
+
+    private void checkFloatInfinity(Floats original, boolean xmlSchemaConforming, String expectedXml) throws Exception
+    {
+        _xmlMapper.configure(ToXmlGenerator.Feature.WRITE_XML_SCHEMA_CONFORMING_FLOATS, xmlSchemaConforming);
+
+        String xml = _xmlMapper.writeValueAsString(original);
+        xml = removeSjsxpNamespace(xml);
+        assertEquals(expectedXml, xml);
+
+        Floats deserialized = _xmlMapper.readValue(xml, Floats.class);
+        assertEquals(original.attr, deserialized.attr);
+        assertEquals(original.elem, deserialized.elem);
+    }
+
+    public void testDoubleInfinity() throws Exception
+    {
+        Doubles infinite = new Doubles();
+        infinite.attr = Double.POSITIVE_INFINITY;
+        infinite.elem = Double.NEGATIVE_INFINITY;
+
+        Doubles finite = new Doubles();
+        finite.attr = 42.5d;
+        finite.elem = 1337.875d;
+
+        checkDoubleInfinity(infinite, false, "<Doubles attr=\"Infinity\"><elem>-Infinity</elem></Doubles>");
+        checkDoubleInfinity(finite, false, "<Doubles attr=\"42.5\"><elem>1337.875</elem></Doubles>");
+        checkDoubleInfinity(infinite, true, "<Doubles attr=\"INF\"><elem>-INF</elem></Doubles>");
+        checkDoubleInfinity(finite, true, "<Doubles attr=\"42.5\"><elem>1337.875</elem></Doubles>");
+    }
+
+    private void checkDoubleInfinity(Doubles original, boolean xmlSchemaConforming, String expectedXml) throws Exception
+    {
+        _xmlMapper.configure(ToXmlGenerator.Feature.WRITE_XML_SCHEMA_CONFORMING_FLOATS, xmlSchemaConforming);
+
+        String xml = _xmlMapper.writeValueAsString(original);
+        xml = removeSjsxpNamespace(xml);
+        assertEquals(expectedXml, xml);
+
+        Doubles deserialized = _xmlMapper.readValue(xml, Doubles.class);
+        assertEquals(original.attr, deserialized.attr);
+        assertEquals(original.elem, deserialized.elem);
+    }
 }