From ec2378b278c463646d9ad9c4fdd9e1057018174c Mon Sep 17 00:00:00 2001
From: belugabehr <12578579+belugabehr@users.noreply.github.com>
Date: Sun, 6 Oct 2024 20:44:04 -0400
Subject: [PATCH] AVRO-4073: Create Convenience toBytes Method for Datum Writer
 (#3197)

---
 .../java/org/apache/avro/io/DatumWriter.java     | 16 ++++++++++++++++
 .../apache/avro/specific/TestSpecificData.java   | 14 ++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/lang/java/avro/src/main/java/org/apache/avro/io/DatumWriter.java b/lang/java/avro/src/main/java/org/apache/avro/io/DatumWriter.java
index f1e57626912..050c25b467f 100644
--- a/lang/java/avro/src/main/java/org/apache/avro/io/DatumWriter.java
+++ b/lang/java/avro/src/main/java/org/apache/avro/io/DatumWriter.java
@@ -17,6 +17,7 @@
  */
 package org.apache.avro.io;
 
+import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 
 import org.apache.avro.Schema;
@@ -36,4 +37,19 @@ public interface DatumWriter<D> {
    * the schema from the datum to the output.
    */
   void write(D datum, Encoder out) throws IOException;
+
+  /**
+   * Convenience method to Write a datum to a byte array. Traverse the schema,
+   * depth first, writing each leaf value in the schema from the datum to the byte
+   * array.
+   *
+   * @param datum The datum to serialize
+   * @return The serialized datum stored in an array of bytes
+   */
+  default byte[] toByteArray(D datum) throws IOException {
+    try (ByteArrayOutputStream out = new ByteArrayOutputStream(128)) {
+      write(datum, EncoderFactory.get().directBinaryEncoder(out, null));
+      return out.toByteArray();
+    }
+  }
 }
diff --git a/lang/java/avro/src/test/java/org/apache/avro/specific/TestSpecificData.java b/lang/java/avro/src/test/java/org/apache/avro/specific/TestSpecificData.java
index 5c8cad85331..1d9d58b0518 100644
--- a/lang/java/avro/src/test/java/org/apache/avro/specific/TestSpecificData.java
+++ b/lang/java/avro/src/test/java/org/apache/avro/specific/TestSpecificData.java
@@ -179,6 +179,20 @@ void nonStringable() throws Exception {
     }
   }
 
+  @Test
+  void testToByteArray() throws Exception {
+    final Schema string = Schema.create(Type.STRING);
+    final DatumWriter<String> writer = new SpecificDatumWriter<>(string);
+
+    try (final ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
+      final Encoder encoder = EncoderFactory.get().directBinaryEncoder(baos, null);
+      writer.write("test", encoder);
+
+      final byte[] bytes = writer.toByteArray("test");
+      assertArrayEquals(baos.toByteArray(), bytes);
+    }
+  }
+
   @Test
   void classNameContainingReservedWords() {
     final Schema schema = Schema.createRecord("AnyName", null, "db.public.table", false);