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

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

@@ -20,6 +20,7 @@
 import com.fasterxml.jackson.core.json.JsonWriteContext;
 import com.fasterxml.jackson.core.util.JacksonFeatureSet;
 import com.fasterxml.jackson.dataformat.xml.XmlPrettyPrinter;
+import com.fasterxml.jackson.dataformat.xml.deser.FromXmlParser;
 import com.fasterxml.jackson.dataformat.xml.util.DefaultXmlPrettyPrinter;
 import com.fasterxml.jackson.dataformat.xml.util.StaxUtil;
 
@@ -106,6 +107,34 @@ 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 FromXmlParser.Feature}.
+         *<p>
+         * Feature is disabled by default for backwards compatibility.
+         */
+        XML_SCHEMA_CONFORMING_FLOATS(false),
         ;
 
         final boolean _defaultState;
@@ -1174,6 +1203,11 @@ public void writeNumber(long l) throws IOException
     @Override
     public void writeNumber(double d) throws IOException
     {
+        if (Double.isInfinite(d) && isEnabled(Feature.XML_SCHEMA_CONFORMING_FLOATS)) {
+            writeNumber(d > 0d ? "INF" : "-INF");
+            return;
+        }
+
         _verifyValueWrite("write number");
         if (_nextName == null) {
             handleMissingName();
@@ -1202,6 +1236,11 @@ public void writeNumber(double d) throws IOException
     @Override
     public void writeNumber(float f) throws IOException
     {
+        if (Float.isInfinite(f) && isEnabled(Feature.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

@@ -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;
@@ -175,4 +191,62 @@ public void testJAXB() throws Exception
         System.out.println("JAXB -> "+sw);
     }
     */
+
+    public void testFloatInfinity() throws IOException
+    {
+        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 IOException
+    {
+        _xmlMapper.configure(ToXmlGenerator.Feature.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 IOException
+    {
+        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 IOException
+    {
+        _xmlMapper.configure(ToXmlGenerator.Feature.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);
+    }
 }