Use generics with signAndGetArtifactSignature

core/src/main/java/tech/pegasys/web3signer/core/service/http/handlers/signing/SignerForIdentifier.java

@@ -44,15 +44,17 @@ public Optional<String> sign(final String identifier, final Bytes data) {
   }
 
   /**
-   * Sign data for given identifier and return ArtifactSignature. Useful for SECP signing.
+   * Sign data for given identifier and return ArtifactSignature. Useful for SECP signing usages.
    *
+   * @param <T> The specific type of ArtifactSignature
    * @param identifier The identifier for which to sign data.
    * @param data Bytes which is signed
-   * @return Optional ArtifactSignature. Empty if no signer available for given identifier
+   * @return Optional ArtifactSignature of type T. Empty if no signer available for given identifier
    */
-  public Optional<ArtifactSignature> signAndGetArtifactSignature(
+  @SuppressWarnings("unchecked")
+  public <T extends ArtifactSignature<?>> Optional<T> signAndGetArtifactSignature(
       final String identifier, final Bytes data) {
-    return signerProvider.getSigner(identifier).map(signer -> signer.sign(data));
+    return signerProvider.getSigner(identifier).map(signer -> (T) signer.sign(data));
   }
 
   /**

core/src/main/java/tech/pegasys/web3signer/core/service/jsonrpc/handlers/signing/TransactionSerializer.java

@@ -78,11 +78,10 @@ private static byte[] prependEip1559TransactionType(byte[] bytesToSign) {
 
   private SignatureData sign(final String eth1Address, final byte[] bytesToSign) {
     final SecpArtifactSignature artifactSignature =
-        (SecpArtifactSignature)
-            secpSigner
-                .signAndGetArtifactSignature(
-                    normaliseIdentifier(eth1Address), Bytes.of(bytesToSign))
-                .orElseThrow(() -> new JsonRpcException(SIGNING_FROM_IS_NOT_AN_UNLOCKED_ACCOUNT));
+        secpSigner
+            .<SecpArtifactSignature>signAndGetArtifactSignature(
+                normaliseIdentifier(eth1Address), Bytes.of(bytesToSign))
+            .orElseThrow(() -> new JsonRpcException(SIGNING_FROM_IS_NOT_AN_UNLOCKED_ACCOUNT));
 
     final Signature signature = artifactSignature.getSignatureData();