Performance improvements for SRA changes. (#4864)

1. Do not call SignerProperty.toString() whenever required properties are read.
2. Check if an SdkHttpRequest is an SdkHttpFullRequest before performing a full conversion to the latter.

Author: millems

core/http-auth-spi/src/main/java/software/amazon/awssdk/http/auth/spi/signer/BaseSignRequest.java

@@ -70,7 +70,7 @@ default <T> boolean hasProperty(SignerProperty<T> property) {
      * The value, {@link T}, is return when present, and an exception is thrown otherwise.
      */
     default <T> T requireProperty(SignerProperty<T> property) {
-        return Validate.notNull(property(property), property.toString() + " must not be null!");
+        return Validate.notNull(property(property), "%s must not be null!", property);
     }
 
     /**

core/sdk-core/src/main/java/software/amazon/awssdk/core/internal/http/pipeline/stages/SigningStage.java

@@ -117,6 +117,18 @@ private <T extends Identity> SdkHttpFullRequest doSraSign(SdkHttpFullRequest req
     private SdkHttpFullRequest toSdkHttpFullRequest(SignedRequest signedRequest) {
         SdkHttpRequest request = signedRequest.request();
 
+        // Optimization: don't do any conversion if we can avoid it.
+        if (request instanceof SdkHttpFullRequest) {
+            SdkHttpFullRequest fullRequest = (SdkHttpFullRequest) request;
+            if (signedRequest.payload().orElse(null) == fullRequest.contentStreamProvider().orElse(null)) {
+                return fullRequest;
+            }
+
+            return fullRequest.toBuilder()
+                              .contentStreamProvider(signedRequest.payload().orElse(null))
+                              .build();
+        }
+
         return SdkHttpFullRequest.builder()
                                  .contentStreamProvider(signedRequest.payload().orElse(null))
                                  .protocol(request.protocol())