NumberFormat support

src/main/java/com/fasterxml/jackson/databind/ser/std/NumberSerializer.java

@@ -4,6 +4,9 @@
 import java.lang.reflect.Type;
 import java.math.BigDecimal;
 import java.math.BigInteger;
+import java.text.DecimalFormat;
+import java.text.DecimalFormatSymbols;
+import java.text.NumberFormat;
 
 import com.fasterxml.jackson.annotation.JsonFormat;
 
@@ -38,13 +41,28 @@ public class NumberSerializer
 
     protected final boolean _isInt;
 
+    /**
+     * @since 2.17
+     */
+    protected final NumberFormat _format;
+
     /**
      * @since 2.5
      */
     public NumberSerializer(Class<? extends Number> rawType) {
         super(rawType, false);
         // since this will NOT be constructed for Integer or Long, only case is:
         _isInt = (rawType == BigInteger.class);
+        _format = null;
+    }
+
+    /**
+     * @since 2.17
+     */
+    public NumberSerializer(NumberSerializer src, NumberFormat format) {
+        super(src);
+        _isInt = src._isInt;
+        _format = format;
     }
 
     @Override
@@ -55,6 +73,21 @@ public JsonSerializer<?> createContextual(SerializerProvider prov,
         if (format != null) {
             switch (format.getShape()) {
             case STRING:
+                if (format.hasPattern()) {
+                    DecimalFormat decimalFormat;
+                    try {
+                        if (format.hasLocale()) {
+                            decimalFormat = new DecimalFormat(format.getPattern(),
+                                    DecimalFormatSymbols.getInstance(format.getLocale()));
+                        } else {
+                            decimalFormat = new DecimalFormat(format.getPattern());
+                        }
+                    } catch (IllegalArgumentException e) {
+                        return prov.reportBadDefinition(handledType(),
+                                String.format("Invalid `DecimalFormat`: \"%s\"", format.getPattern()));
+                    }
+                    return new NumberSerializer(this, decimalFormat);
+                }
                 // [databind#2264]: Need special handling for `BigDecimal`
                 if (((Class<?>) handledType()) == BigDecimal.class) {
                     return bigDecimalAsStringSerializer();
@@ -69,6 +102,10 @@ public JsonSerializer<?> createContextual(SerializerProvider prov,
     @Override
     public void serialize(Number value, JsonGenerator g, SerializerProvider provider) throws IOException
     {
+        if (_format != null) {
+            g.writeString(_format.format(value));
+            return;
+        }
         // should mostly come in as one of these two:
         if (value instanceof BigDecimal) {
             g.writeNumber((BigDecimal) value);

src/test/java/com/fasterxml/jackson/databind/format/NumberFormatTest.java

@@ -0,0 +1,53 @@
+package com.fasterxml.jackson.databind.format;
+
+import com.fasterxml.jackson.annotation.JsonFormat;
+import com.fasterxml.jackson.databind.BaseMapTest;
+import com.fasterxml.jackson.databind.JsonMappingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.junit.Assert;
+
+import java.math.BigDecimal;
+
+import java.util.Locale;
+import java.util.TimeZone;
+
+public class NumberFormatTest extends BaseMapTest
+{
+    protected static class NumberWrapper {
+
+        public BigDecimal value;
+
+        public NumberWrapper() {}
+        public NumberWrapper(BigDecimal v) { value = v; }
+    }
+
+    public void testTypeDefaults() throws Exception
+    {
+        ObjectMapper mapper = newJsonMapper();
+        mapper.configOverride(BigDecimal.class)
+            .setFormat(new JsonFormat.Value("00,000.00", JsonFormat.Shape.STRING, (Locale) null, (TimeZone) null, null, null));
+        String json = mapper.writeValueAsString(new NumberWrapper(new BigDecimal("1234")));
+        assertEquals(a2q("{'value':'01,234.00'}"), json);
+
+        // and then read back is not supported yet.
+        /*NumberWrapper w = mapper.readValue(a2q("{'value':'01,234.00'}"), NumberWrapper.class);
+        assertNotNull(w);
+        assertEquals(new BigDecimal("1234"), w.value);*/
+    }
+
+    protected static class InvalidPatternWrapper {
+        @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "#,##0.#.#")
+        public BigDecimal value;
+
+        public InvalidPatternWrapper(BigDecimal value) {
+            this.value = value;
+        }
+    }
+
+    public void testInvalidPattern() throws Exception {
+        ObjectMapper mapper = newJsonMapper();
+        Assert.assertThrows(JsonMappingException.class, () -> {
+            mapper.writeValueAsString(new InvalidPatternWrapper(BigDecimal.ZERO));
+        });
+    }
+}