add serializer and deserializer for Signature (#305)

* add serializer and deserializer for `Signature`
* WrappedSignature example interface and test
* fix checkstyle
* add `as = ImmutableSignature.class` back

Co-authored-by: David Fuelling <[email protected]>

xrpl4j-crypto-parent/xrpl4j-crypto-core/src/main/java/org/xrpl/xrpl4j/crypto/core/signing/Signature.java

@@ -12,8 +12,8 @@
  * Represents a digital signature for a transaction that can be submitted to the XRP Ledger.
  */
 @Value.Immutable
-@JsonSerialize(as = ImmutableSignature.class)
-@JsonDeserialize(as = ImmutableSignature.class)
+@JsonSerialize(as = ImmutableSignature.class, using = SignatureSerializer.class)
+@JsonDeserialize(as = ImmutableSignature.class, using = SignatureDeserializer.class)
 public interface Signature {
 
   /**

xrpl4j-crypto-parent/xrpl4j-crypto-core/src/main/java/org/xrpl/xrpl4j/crypto/core/signing/SignatureDeserializer.java

@@ -0,0 +1,22 @@
+package org.xrpl.xrpl4j.crypto.core.signing;
+
+import com.fasterxml.jackson.core.JsonParser;
+import com.fasterxml.jackson.databind.DeserializationContext;
+import com.fasterxml.jackson.databind.JsonDeserializer;
+import com.fasterxml.jackson.databind.JsonNode;
+import org.xrpl.xrpl4j.codec.addresses.UnsignedByteArray;
+
+import java.io.IOException;
+
+/**
+ * Deserializes signature string value to an object of type {@link Signature}.
+ */
+class SignatureDeserializer extends JsonDeserializer<Signature> {
+
+  @Override
+  public Signature deserialize(JsonParser jsonParser, DeserializationContext ctxt)
+    throws IOException {
+    JsonNode node = jsonParser.getCodec().readTree(jsonParser);
+    return Signature.builder().value(UnsignedByteArray.fromHex(node.asText())).build();
+  }
+}

xrpl4j-crypto-parent/xrpl4j-crypto-core/src/main/java/org/xrpl/xrpl4j/crypto/core/signing/SignatureSerializer.java

@@ -0,0 +1,17 @@
+package org.xrpl.xrpl4j.crypto.core.signing;
+
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.databind.JsonSerializer;
+import com.fasterxml.jackson.databind.SerializerProvider;
+
+import java.io.IOException;
+
+/**
+ * Custom Jackson serializer for {@link Signature}es.
+ */
+class SignatureSerializer extends JsonSerializer<Signature> {
+  @Override
+  public void serialize(Signature signature, JsonGenerator gen, SerializerProvider provider) throws IOException {
+    gen.writeString(signature.base16Value());
+  }
+}

xrpl4j-crypto-parent/xrpl4j-crypto-core/src/main/java/org/xrpl/xrpl4j/crypto/core/signing/UnsignedByteArrayDeserializer.java

@@ -8,7 +8,7 @@
 import java.io.IOException;
 
 /**
- * A FasterXML serializer for {@link UnsignedByteArray}.
+ * A FasterXML deserializer for {@link UnsignedByteArray}.
  *
  * @deprecated This class will go away once {@link UnsignedByteArray} is moved into the core module.
  */

xrpl4j-crypto-parent/xrpl4j-crypto-core/src/test/java/org/xrpl/xrpl4j/crypto/core/signing/SignatureTest.java

@@ -4,7 +4,11 @@
 import static org.hamcrest.Matchers.is;
 
 import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
+import com.fasterxml.jackson.databind.annotation.JsonSerialize;
 import com.jayway.jsonassert.JsonAssert;
+import org.immutables.value.Value;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.xrpl.xrpl4j.codec.addresses.UnsignedByteArray;
@@ -46,7 +50,8 @@ void hexValue() {
   @Test
   void jsonSerializeAndDeserialize() throws JsonProcessingException {
     String json = ObjectMapperFactory.create().writeValueAsString(signature);
-    JsonAssert.with(json).assertThat("$.value", is(HEX_32_BYTES));
+    JsonAssert.with(json).assertThat("$", is(HEX_32_BYTES));
+    assertThat(json).isEqualTo("\"" + HEX_32_BYTES + "\"");
 
     Signature actual = ObjectMapperFactory.create().readValue(json, Signature.class);
     assertThat(actual).isEqualTo(signature);
@@ -61,4 +66,36 @@ void of() {
   void fromBase16() {
     assertThat(Signature.fromBase16(HEX_32_BYTES)).isEqualTo(signature);
   }
+
+  @Test
+  void serializeSignature() throws JsonProcessingException {
+
+    ObjectMapper objectMapper = ObjectMapperFactory.create();
+
+    WrappedSignature wrappedSignature = WrappedSignature.builder()
+      .signature(signature)
+      .build();
+    String serializedWrappedSignature = objectMapper.writeValueAsString(wrappedSignature);
+
+    String serialized = "{\"signature\":\"" + HEX_32_BYTES + "\"}";
+    assertThat(serializedWrappedSignature).isEqualTo(serialized);
+
+    WrappedSignature deserializedWrappedSignature = objectMapper.readValue(
+      serializedWrappedSignature, WrappedSignature.class
+    );
+    assertThat(deserializedWrappedSignature).isEqualTo(wrappedSignature);
+
+  }
+
+  @Value.Immutable
+  @JsonSerialize(as = ImmutableWrappedSignature.class)
+  @JsonDeserialize(as = ImmutableWrappedSignature.class)
+  interface WrappedSignature {
+
+    static ImmutableWrappedSignature.Builder builder() {
+      return ImmutableWrappedSignature.builder();
+    }
+
+    Signature signature();
+  }
 }