Support decoding Number

serde-api/src/main/java/io/micronaut/serde/Decoder.java

@@ -174,6 +174,28 @@ default Character decodeCharNullable() throws IOException {
         return decodeNull() ? null : decodeChar();
     }
 
+    /**
+     * Decodes a number.
+     * @return The number
+     * @throws IOException If an unrecoverable error occurs
+     * @since 2.9.0
+     */
+    default Number decodeNumber() throws IOException {
+        return decodeBigDecimal();
+    }
+
+    /**
+     * Equivalent to {@code decodeNull() ? null : decodeNumber()}.
+     *
+     * @return The number
+     * @throws IOException If an unrecoverable error occurs
+     * @since 2.9.0
+     */
+    @Nullable
+    default Number decodeNumberNullable() throws IOException {
+        return decodeNull() ? null : decodeNumber();
+    }
+
     /**
      * Decodes a int.
      * @return The int

serde-jackson-tck/src/main/groovy/io/micronaut/serde/jackson/JsonPropertySpec.groovy

@@ -5,6 +5,43 @@ import spock.lang.Unroll
 
 class JsonPropertySpec extends JsonCompileSpec {
 
+    @Unroll
+    void "serde Number"(Number number) {
+        given:
+            def context = buildContext('example.Test', '''
+package example;
+
+import io.micronaut.core.annotation.Introspected;
+import io.micronaut.core.annotation.Nullable;
+import java.util.Optional;
+
+@io.micronaut.serde.annotation.Serdeable
+@Introspected(accessKind = Introspected.AccessKind.FIELD)
+class Test {
+    public Number foo;
+}
+''', [:])
+        beanUnderTest.@foo = number
+
+        expect:
+            jsonMapper.readValue(json, typeUnderTest).@foo == result
+            writeJson(jsonMapper, beanUnderTest) == json
+
+        cleanup:
+            context.close()
+
+        where:
+            number                      || result                      || json
+            123.456                     || 123.456                     || '{"foo":123.456}'
+            Double.valueOf(123.123)     || Double.valueOf(123.123)     || '{"foo":123.123}'
+            Float.valueOf(123.123)      || Double.valueOf(123.123)     || '{"foo":123.123}'
+            BigDecimal.valueOf(123.123) || BigDecimal.valueOf(123.123) || '{"foo":123.123}'
+            Integer.valueOf(123)        || Integer.valueOf(123)        || '{"foo":123}'
+            Short.valueOf((short) 123)  || Short.valueOf((short) 123)  || '{"foo":123}'
+            BigInteger.valueOf(123)     || BigInteger.valueOf(123)     || '{"foo":123}'
+
+    }
+
     void "missing nullable properties are not overwritten"() {
         given:
             def context = buildContext('example.Test', '''

serde-jackson/src/main/java/io/micronaut/serde/jackson/JacksonDecoder.java

@@ -774,11 +774,20 @@ public BigDecimal decodeBigDecimalNullable() throws IOException {
         }
     }
 
-    private Number decodeNumber() throws IOException {
+    private Number doDecodeNumber() throws IOException {
         nextToken();
         return parser.getNumberValue();
     }
 
+    @Override
+    public Number decodeNumber() throws IOException {
+        return switch (peekToken()) {
+            case VALUE_STRING -> decodeBigDecimal();
+            case VALUE_NUMBER_INT, VALUE_NUMBER_FLOAT -> doDecodeNumber();
+            default -> throw unexpectedToken(JsonToken.VALUE_NUMBER_INT, nextToken());
+        };
+    }
+
     @Override
     public byte @NonNull [] decodeBinary() throws IOException {
         return switch (peekToken()) {
@@ -969,7 +978,7 @@ ArbitraryBuilder proceed() throws IOException {
                         return this;
                     }
                     case VALUE_NUMBER_INT, VALUE_NUMBER_FLOAT -> {
-                        put(key, elementDecoder.decodeNumber());
+                        put(key, elementDecoder.doDecodeNumber());
                         return this;
                     }
                     case VALUE_TRUE, VALUE_FALSE -> {

serde-support/src/main/java/io/micronaut/serde/support/serdes/NumberTypeSerde.java

@@ -0,0 +1,82 @@
+/*
+ * Copyright 2017-2024 original authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.micronaut.serde.support.serdes;
+
+import io.micronaut.core.annotation.Internal;
+import io.micronaut.core.annotation.NonNull;
+import io.micronaut.core.annotation.Nullable;
+import io.micronaut.core.type.Argument;
+import io.micronaut.serde.Decoder;
+import io.micronaut.serde.Encoder;
+import io.micronaut.serde.exceptions.SerdeException;
+import io.micronaut.serde.support.SerdeRegistrar;
+
+import java.io.IOException;
+import java.math.BigDecimal;
+import java.math.BigInteger;
+
+@Internal
+final class NumberTypeSerde implements SerdeRegistrar<Number>, NumberSerde<Number> {
+
+    @Override
+    public Argument<Number> getType() {
+        return Argument.of(Number.class);
+    }
+
+    @Override
+    public Number deserialize(Decoder decoder,
+                              DecoderContext decoderContext,
+                              Argument<? super Number> type) throws IOException {
+        return decoder.decodeNumber();
+    }
+
+    @Override
+    public Number deserializeNullable(@NonNull Decoder decoder, @NonNull DecoderContext context, @NonNull Argument<? super Number> type) throws IOException {
+        return decoder.decodeNumberNullable();
+    }
+
+    @Override
+    public void serialize(Encoder encoder,
+                          EncoderContext context,
+                          Argument<? extends Number> type,
+                          Number value) throws IOException {
+        if (value instanceof Integer integer) {
+            encoder.encodeInt(integer);
+        } else if (value instanceof Long aLong) {
+            encoder.encodeLong(aLong);
+        } else if (value instanceof Double aDouble) {
+            encoder.encodeDouble(aDouble);
+        } else if (value instanceof Float aFloat) {
+            encoder.encodeFloat(aFloat);
+        } else if (value instanceof Byte aByte) {
+            encoder.encodeByte(aByte);
+        } else if (value instanceof Short aShort) {
+            encoder.encodeShort(aShort);
+        } else if (value instanceof BigDecimal bigDecimal) {
+            encoder.encodeBigDecimal(bigDecimal);
+        } else if (value instanceof BigInteger bigInteger) {
+            encoder.encodeBigInteger(bigInteger);
+        } else {
+            throw new SerdeException("Unrecognized Number type: " + value.getClass().getName() + " " + value);
+        }
+    }
+
+    @Nullable
+    @Override
+    public Integer getDefaultValue(@NonNull DecoderContext context, @NonNull Argument<? super Number> type) {
+        return type.isPrimitive() ? 0 : null;
+    }
+}

serde-support/src/main/java/io/micronaut/serde/support/serdes/Serdes.java

@@ -98,7 +98,8 @@ public final class Serdes {
         new PeriodSerde(),
         new ByteBufferSerde(),
         new StringArraySerde(),
-        new OptionalSerde<>()
+        new OptionalSerde<>(),
+        new NumberTypeSerde()
     );
 
     public static void register(SerdeConfiguration serdeConfiguration,