Support custom serdes for builtin types (#459)

Fixes #312

serde-jackson/src/test/groovy/io/micronaut/serde/jackson/CustomStringSerdeSpec.groovy

@@ -0,0 +1,60 @@
+package io.micronaut.serde.jackson
+
+import io.micronaut.core.annotation.NonNull
+import io.micronaut.core.annotation.Order
+import io.micronaut.core.type.Argument
+import io.micronaut.core.util.StringUtils
+import io.micronaut.serde.Decoder
+import io.micronaut.serde.Deserializer
+import io.micronaut.serde.Encoder
+import io.micronaut.serde.ObjectMapper
+import io.micronaut.serde.Serde
+import io.micronaut.serde.Serializer
+import io.micronaut.serde.annotation.Serdeable
+import io.micronaut.test.annotation.MockBean
+import io.micronaut.test.extensions.spock.annotation.MicronautTest
+import jakarta.inject.Inject
+import spock.lang.Specification
+
+@MicronautTest
+class CustomStringSerdeSpec extends Specification {
+
+    @Inject ObjectMapper objectMapper
+
+    void "test custom string encoder"() {
+        expect:
+        objectMapper.writeValueAsString(new Test(name: "Fred")) == '{"name":"derF"}'
+        objectMapper.writeValueAsString(new Test(name: "")) == '{"name":null}'
+        objectMapper.writeValueAsString(new Test(name: "   ")) == '{"name":null}'
+        objectMapper.readValue('{"name":"derF"}', Test).name == "Fred"
+
+    }
+
+    @Serdeable
+    static class Test {
+        String name
+    }
+
+    @MockBean
+    Serde<String> stringSerde() {
+        return new Serde<String>() {
+            @Override
+            String deserialize(@NonNull Decoder decoder, @NonNull Deserializer.DecoderContext context, @NonNull Argument<? super String> type) throws IOException {
+                if (decoder.decodeNull()) {
+                    return null
+                } else {
+                    return decoder.decodeString().reverse()
+                }
+            }
+
+            @Override
+            void serialize(@NonNull Encoder encoder, @NonNull Serializer.EncoderContext context, @NonNull Argument<? extends String> type, @NonNull String value) throws IOException {
+                if (StringUtils.isEmpty(value.trim())) {
+                    encoder.encodeNull()
+                } else {
+                    encoder.encodeString(value.reverse())
+                }
+            }
+        }
+    }
+}

serde-support/src/main/java/io/micronaut/serde/support/DefaultSerdeRegistry.java

@@ -180,8 +180,16 @@ private void registerPrimitiveSerdes() {
     }
 
     private void registerBuiltInSerdes() {
-        this.deserializerMap.put(new TypeKey(Argument.STRING),
-                                 (NullableDeserializer<String>) (decoder, decoderContext, type) -> decoder.decodeString());
+        if (!this.deserializerDefMap.containsKey(String.class)) {
+            TypeKey tk = new TypeKey(Argument.STRING);
+            this.deserializerMap.put(tk,
+                (NullableDeserializer<String>) (decoder, decoderContext, type) -> decoder.decodeString());
+        }
+        if (!this.deserializerDefMap.containsKey(CharSequence.class)) {
+            TypeKey tk = new TypeKey(Argument.of(CharSequence.class));
+            this.deserializerMap.put(tk,
+                (NullableDeserializer<CharSequence>) (decoder, decoderContext, type) -> decoder.decodeString());
+        }
         Stream.of(
                 new IntegerSerde(),
                 new LongSerde(),
@@ -214,8 +222,12 @@ private void registerBuiltInSerdes() {
     private void register(SerdeRegistrar<?> serdeRegistrar) {
         for (Argument<?> type : serdeRegistrar.getTypes()) {
             final TypeKey typeEntry = new TypeKey(type);
-            DefaultSerdeRegistry.this.deserializerMap.put(typeEntry, serdeRegistrar);
-            DefaultSerdeRegistry.this.serializerMap.put(typeEntry, serdeRegistrar);
+            if (!DefaultSerdeRegistry.this.deserializerMap.containsKey(typeEntry)) {
+                DefaultSerdeRegistry.this.deserializerMap.put(typeEntry, serdeRegistrar);
+            }
+            if (!DefaultSerdeRegistry.this.serializerMap.containsKey(typeEntry)) {
+                DefaultSerdeRegistry.this.serializerMap.put(typeEntry, serdeRegistrar);
+            }
         }
     }
 

serde-support/src/main/java/io/micronaut/serde/support/deserializers/CoreDeserializers.java

@@ -48,17 +48,6 @@
 @Factory
 public class CoreDeserializers {
 
-    /**
-     * Deserializes string types.
-     *
-     * @return The string deserializer
-     */
-    @Singleton
-    @NonNull
-    protected Deserializer<String> stringDeserializer() {
-        return new StringDeserializer();
-    }
-
     /**
      * Deserializes array lists.
      *
@@ -189,22 +178,6 @@ protected <V> Deserializer<Optional<V>> optionalDeserializer() {
         return new OptionalDeserializer<>();
     }
 
-    private static class StringDeserializer implements Deserializer<String> {
-
-        @Override
-        public String deserialize(Decoder decoder, DecoderContext decoderContext, Argument<? super String> type) throws IOException {
-            if (decoder.decodeNull()) {
-                return null;
-            }
-            return decoder.decodeString();
-        }
-
-        @Override
-        public boolean allowNull() {
-            return true;
-        }
-    }
-
     private static class OptionalDeserializer<V> implements CustomizableDeserializer<Optional<V>> {
 
         @Override

settings.gradle.kts

@@ -6,7 +6,7 @@ pluginManagement {
 }
 
 plugins {
-    id("io.micronaut.build.shared.settings") version "5.3.16"
+    id("io.micronaut.build.shared.settings") version "5.4.9"
 }
 
 enableFeaturePreview("TYPESAFE_PROJECT_ACCESSORS")