Add blob support to NodeMapper

This adds blob support to NodeMapper, serializing to and from base64
encoded string nodes.

Author: JordonPhillips

.changes/next-release/feature-783557f3624987ca34a0269dc18e0b8aa6e4a19f.json

@@ -0,0 +1,7 @@
+{
+  "type": "feature",
+  "description": "Added support for (de)serializing byte arrays to/from base64-encoded string nodes to `NodeMapper`.",
+  "pull_requests": [
+    "[#2803](https://github.com/smithy-lang/smithy/pull/2803)"
+  ]
+}

smithy-model/src/main/java/software/amazon/smithy/model/node/DefaultNodeDeserializers.java

@@ -20,9 +20,11 @@
 import java.math.BigInteger;
 import java.net.URI;
 import java.net.URL;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.ArrayList;
+import java.util.Base64;
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -603,6 +605,21 @@ private interface FromStringClassFactory {
         };
     };
 
+    // Creates a byte array from a base64-encoded string node.
+    private static final ObjectCreatorFactory BYTES_CREATOR = (nodeType, target, nodeMapper) -> {
+        if (nodeType != NodeType.STRING || target != byte[].class) {
+            return null;
+        }
+        return (node, targetType, pointer, mapper) -> {
+            String value = node.expectStringNode().getValue();
+            try {
+                return Base64.getDecoder().decode(value.getBytes(StandardCharsets.UTF_8));
+            } catch (Exception e) {
+                throw NodeDeserializationException.fromContext(targetType, pointer, node, e, e.getMessage());
+            }
+        };
+    };
+
     // The priority ordered list of default factories that NodeMapper uses.
     // The priority is determined based on the specificity of each deserializer;
     // the most specific ones should appear at the start of the list, and the
@@ -615,6 +632,7 @@ private interface FromStringClassFactory {
             NULL_CREATOR,
             FROM_NODE_CREATOR,
             BOOLEAN_CREATOR_FACTORY,
+            BYTES_CREATOR,
             FROM_STRING,
             STRING_CREATOR,
             ENUM_CREATOR,

smithy-model/src/main/java/software/amazon/smithy/model/node/DefaultNodeSerializers.java

@@ -14,6 +14,7 @@
 import java.net.URL;
 import java.nio.file.Path;
 import java.util.ArrayList;
+import java.util.Base64;
 import java.util.Comparator;
 import java.util.HashSet;
 import java.util.LinkedHashMap;
@@ -84,6 +85,19 @@ public Node serialize(Number value, Set<Object> serializedObjects, NodeMapper ma
         }
     };
 
+    // Serializes a byte array into a base64-encoded string node.
+    private static final Serializer<byte[]> BLOB_SERIALIZER = new Serializer<byte[]>() {
+        @Override
+        public Class<byte[]> getType() {
+            return byte[].class;
+        }
+
+        @Override
+        public Node serialize(byte[] value, Set<Object> serializedObjects, NodeMapper mapper) {
+            return Node.from(Base64.getEncoder().encodeToString(value));
+        }
+    };
+
     // Serialize a String into a StringNode.
     private static final Serializer<String> STRING_SERIALIZER = new Serializer<String>() {
         @Override
@@ -392,6 +406,7 @@ private boolean canSerialize(NodeMapper mapper, Node value) {
     static final List<Serializer> SERIALIZERS = ListUtils.of(
             TO_NODE_SERIALIZER,
             OPTIONAL_SERIALIZER,
+            BLOB_SERIALIZER,
             STRING_SERIALIZER,
             BOOLEAN_SERIALIZER,
             NUMBER_SERIALIZER,

smithy-model/src/test/java/software/amazon/smithy/model/node/NodeMapperTest.java

@@ -16,10 +16,12 @@
 import static org.hamcrest.Matchers.not;
 import static org.hamcrest.Matchers.nullValue;
 import static org.hamcrest.Matchers.startsWith;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 import java.io.File;
 import java.net.URI;
 import java.net.URL;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -1634,4 +1636,34 @@ public Map<ShapeId, List<Map<ShapeId, ShapeType>>> getShapeTypes() {
             return shapeTypes;
         }
     }
+
+    @Test
+    public void serializesBytesToBase64StringNode() {
+        NodeMapper mapper = new NodeMapper();
+        Node input = Node.objectNode().withMember("bytes", "Zm9v");
+        HasBytes result = mapper.deserialize(input, HasBytes.class);
+        String decoded = new String(result.getBytes(), StandardCharsets.UTF_8);
+        assertEquals("foo", decoded);
+    }
+
+    @Test
+    public void deserializesBytesFromBase64StringNode() {
+        NodeMapper mapper = new NodeMapper();
+        HasBytes input = new HasBytes();
+        input.setBytes("foo".getBytes(StandardCharsets.UTF_8));
+        ObjectNode result = mapper.serialize(input).expectObjectNode();
+        assertEquals("Zm9v", result.expectStringMember("bytes").getValue());
+    }
+
+    public static final class HasBytes {
+        private byte[] bytes;
+
+        public byte[] getBytes() {
+            return bytes;
+        }
+
+        public void setBytes(byte[] bytes) {
+            this.bytes = bytes;
+        }
+    }
 }