Add awsGeneratedTags field to S3Bucket in s3-event-notifications

Amazon S3 event notifications delivered to SNS, SQS, and Lambda now
include an `awsGeneratedTags` map on the `bucket` object when system
tags are enabled on the source bucket. The Java SDK model did not
round-trip this field, so consumers had to fall back to raw JSON
parsing to read the tags.

This change adds `Map<String, String> awsGeneratedTags` to `S3Bucket`
and threads it through the reader and writer:

  * `S3Bucket`: adds `awsGeneratedTags` field with a getter, a new
    four-argument constructor, and updates `equals`/`hashCode`/
    `toString`. The pre-existing three-argument constructor is
    preserved so existing callers are source- and behavior-compatible.
    Tags are defensively copied on construction and returned as an
    unmodifiable view.
  * `DefaultS3EventNotificationReader`: parses `awsGeneratedTags` as
    `Map<String, String>`. Absent field yields `null`. Null value
    entries are preserved. Non-string values throw
    `IllegalArgumentException` with a helpful message including the
    offending key and value.
  * `DefaultS3EventNotificationWriter`: emits `awsGeneratedTags` only
    when the map is non-null and non-empty, matching S3's server-side
    `@JsonInclude(NON_EMPTY)` behavior so round-tripped output is
    indistinguishable from what S3 emits.

Also bumps `eventVersion` fixtures in the module test files from
`2.4` to `2.5` to reflect the schema version emitted alongside this
launch.

The change is fully additive:
  * Older SDKs remain compatible with new payloads (unknown fields
    are ignored during parse).
  * Newer SDKs remain compatible with old payloads
    (`getAwsGeneratedTags()` returns `null` when the field is absent).

Author: ylyu-eng

.changes/next-release/feature-S3EventNotification-6d2df07.json

@@ -0,0 +1,6 @@
+{
+    "type": "feature",
+    "category": "S3 Event Notification",
+    "contributor": "",
+    "description": "Added `awsGeneratedTags` field to `S3Bucket` in the S3 Event Notifications module. Amazon S3 emits AWS-generated system tags on the `bucket` portion of event notifications when system tags are enabled on the source bucket. SDK consumers on the SNS/SQS/Lambda delivery paths can now access these tags via `S3Bucket#getAwsGeneratedTags()`."
+}

services-custom/s3-event-notifications/src/main/java/software/amazon/awssdk/eventnotifications/s3/internal/DefaultS3EventNotificationReader.java

@@ -20,6 +20,7 @@
 import java.nio.charset.StandardCharsets;
 import java.time.Instant;
 import java.util.Collections;
+import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.stream.Collectors;
@@ -242,7 +243,29 @@ private S3Bucket readBucket(JsonNode jsonNode) {
         String name = expectStringOrNull(bucketNode, "name");
         UserIdentity ownerIdentity = readOwnerIdentity(bucketNode.get("ownerIdentity"));
         String arn = expectStringOrNull(bucketNode, "arn");
-        return new S3Bucket(name, ownerIdentity, arn);
+        Map<String, String> awsGeneratedTags = readStringMapOrNull(bucketNode.get("awsGeneratedTags"), "awsGeneratedTags");
+        return new S3Bucket(name, ownerIdentity, arn, awsGeneratedTags);
+    }
+
+    private Map<String, String> readStringMapOrNull(JsonNode jsonNode, String name) {
+        Map<String, JsonNode> mapNode = expectObjectOrNull(jsonNode, name);
+        if (mapNode == null) {
+            return null;
+        }
+        Map<String, String> result = new LinkedHashMap<>();
+        mapNode.forEach((tagKey, tagValueNode) ->
+                            result.put(tagKey, readTagStringValueOrNull(name, tagKey, tagValueNode)));
+        return result;
+    }
+
+    private String readTagStringValueOrNull(String mapName, String tagKey, JsonNode tagValue) {
+        if (isNull(tagValue)) {
+            return null;
+        }
+        Validate.isTrue(tagValue.isString(),
+                        "The value of tag '%s' in '%s' was not a string, but was: %s",
+                        tagKey, mapName, tagValue);
+        return tagValue.asString();
     }
 
     private UserIdentity readOwnerIdentity(JsonNode jsonNode) {

services-custom/s3-event-notifications/src/main/java/software/amazon/awssdk/eventnotifications/s3/internal/DefaultS3EventNotificationWriter.java

@@ -19,6 +19,7 @@
 import java.time.Instant;
 import java.time.format.DateTimeFormatter;
 import java.util.List;
+import java.util.Map;
 import software.amazon.awssdk.annotations.SdkInternalApi;
 import software.amazon.awssdk.eventnotifications.s3.model.GlacierEventData;
 import software.amazon.awssdk.eventnotifications.s3.model.IntelligentTieringEventData;
@@ -227,6 +228,17 @@ private void writeS3Bucket(JsonWriter writer, S3Bucket bucket) {
             writer.writeEndObject();
         }
         writeStringField(writer, "arn", bucket.getArn());
+        Map<String, String> awsGeneratedTags = bucket.getAwsGeneratedTags();
+        if (awsGeneratedTags != null && !awsGeneratedTags.isEmpty()) {
+            writeStringMap(writer, "awsGeneratedTags", awsGeneratedTags);
+        }
+        writer.writeEndObject();
+    }
+
+    private void writeStringMap(JsonWriter writer, String field, Map<String, String> map) {
+        writer.writeFieldName(field);
+        writer.writeStartObject();
+        map.forEach((k, v) -> writeStringField(writer, k, v));
         writer.writeEndObject();
     }
 

services-custom/s3-event-notifications/src/main/java/software/amazon/awssdk/eventnotifications/s3/model/S3Bucket.java

@@ -16,6 +16,9 @@
 package software.amazon.awssdk.eventnotifications.s3.model;
 
 
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.Map;
 import java.util.Objects;
 import software.amazon.awssdk.annotations.SdkPublicApi;
 import software.amazon.awssdk.utils.ToString;
@@ -29,11 +32,19 @@ public class S3Bucket {
     private final String name;
     private final UserIdentity ownerIdentity;
     private final String arn;
+    private final Map<String, String> awsGeneratedTags;
 
     public S3Bucket(String name, UserIdentity ownerIdentity, String arn) {
+        this(name, ownerIdentity, arn, null);
+    }
+
+    public S3Bucket(String name, UserIdentity ownerIdentity, String arn, Map<String, String> awsGeneratedTags) {
         this.name = name;
         this.ownerIdentity = ownerIdentity;
         this.arn = arn;
+        this.awsGeneratedTags = awsGeneratedTags == null
+                                ? null
+                                : Collections.unmodifiableMap(new LinkedHashMap<>(awsGeneratedTags));
     }
 
     /**
@@ -57,6 +68,14 @@ public String getArn() {
         return arn;
     }
 
+    /**
+     * @return The AWS-generated system tags for the bucket, or {@code null} if not present in the event. The returned map
+     *         is unmodifiable.
+     */
+    public Map<String, String> getAwsGeneratedTags() {
+        return awsGeneratedTags;
+    }
+
     @Override
     public boolean equals(Object o) {
         if (this == o) {
@@ -74,23 +93,30 @@ public boolean equals(Object o) {
         if (!Objects.equals(ownerIdentity, s3Bucket.ownerIdentity)) {
             return false;
         }
-        return Objects.equals(arn, s3Bucket.arn);
+        if (!Objects.equals(arn, s3Bucket.arn)) {
+            return false;
+        }
+        return Objects.equals(awsGeneratedTags, s3Bucket.awsGeneratedTags);
     }
 
     @Override
     public int hashCode() {
         int result = name != null ? name.hashCode() : 0;
         result = 31 * result + (ownerIdentity != null ? ownerIdentity.hashCode() : 0);
         result = 31 * result + (arn != null ? arn.hashCode() : 0);
+        result = 31 * result + (awsGeneratedTags != null ? awsGeneratedTags.hashCode() : 0);
         return result;
     }
 
     @Override
     public String toString() {
-        return ToString.builder("S3Bucket")
-                       .add("name", name)
-                       .add("ownerIdentity", ownerIdentity)
-                       .add("arn", arn)
-                       .build();
+        ToString builder = ToString.builder("S3Bucket")
+                                   .add("name", name)
+                                   .add("ownerIdentity", ownerIdentity)
+                                   .add("arn", arn);
+        if (awsGeneratedTags != null) {
+            builder.add("awsGeneratedTags", awsGeneratedTags);
+        }
+        return builder.build();
     }
 }

services-custom/s3-event-notifications/src/test/java/software/amazon/awssdk/eventnotifications/s3/internal/EqualsAndHashCodeTest.java

@@ -15,9 +15,8 @@
 
 package software.amazon.awssdk.eventnotifications.s3.internal;
 
-import nl.jqno.equalsverifier.Warning;
-
 import nl.jqno.equalsverifier.EqualsVerifier;
+import nl.jqno.equalsverifier.Warning;
 import org.junit.jupiter.api.Test;
 
 class EqualsAndHashCodeTest {

services-custom/s3-event-notifications/src/test/java/software/amazon/awssdk/eventnotifications/s3/model/S3BucketTest.java

@@ -0,0 +1,82 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ * or in the "license" file accompanying this file. This file is distributed
+ * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ * express or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+package software.amazon.awssdk.eventnotifications.s3.model;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+class S3BucketTest {
+
+    @Test
+    void awsGeneratedTags_nullInput_returnsNull() {
+        S3Bucket bucket = new S3Bucket("name", new UserIdentity("p"), "arn", null);
+        assertThat(bucket.getAwsGeneratedTags()).isNull();
+    }
+
+    @Test
+    void threeArgConstructor_leavesAwsGeneratedTagsNull() {
+        S3Bucket bucket = new S3Bucket("name", new UserIdentity("p"), "arn");
+        assertThat(bucket.getAwsGeneratedTags()).isNull();
+    }
+
+    @Test
+    void toString_omitsAwsGeneratedTags_whenNull() {
+        S3Bucket bucket = new S3Bucket("mybucket", new UserIdentity("p"), "arn:aws:s3:::mybucket");
+        assertThat(bucket.toString()).doesNotContain("awsGeneratedTags");
+    }
+
+    @Test
+    void toString_includesAwsGeneratedTags_whenPresent() {
+        Map<String, String> tags = new LinkedHashMap<>();
+        tags.put("aws:resource:owner", "123456789012");
+        tags.put("aws:resource:region", "us-west-2");
+
+        S3Bucket bucket = new S3Bucket("mybucket", new UserIdentity("p"), "arn:aws:s3:::mybucket", tags);
+        assertThat(bucket.toString())
+            .contains("awsGeneratedTags={aws:resource:owner=123456789012, aws:resource:region=us-west-2}");
+    }
+
+    @Test
+    void awsGeneratedTags_isDefensivelyCopied() {
+        Map<String, String> tags = new LinkedHashMap<>();
+        tags.put("aws:resource:owner", "123456789012");
+
+        S3Bucket bucket = new S3Bucket("mybucket", new UserIdentity("p"), "arn:aws:s3:::mybucket", tags);
+
+        // Mutating the caller's map after construction must not affect the bucket.
+        tags.put("aws:resource:region", "us-west-2");
+        tags.remove("aws:resource:owner");
+
+        assertThat(bucket.getAwsGeneratedTags())
+            .containsExactly(new java.util.AbstractMap.SimpleEntry<>("aws:resource:owner", "123456789012"));
+    }
+
+    @Test
+    void getAwsGeneratedTags_isUnmodifiable() {
+        Map<String, String> tags = new LinkedHashMap<>();
+        tags.put("aws:resource:owner", "123456789012");
+
+        S3Bucket bucket = new S3Bucket("mybucket", new UserIdentity("p"), "arn:aws:s3:::mybucket", tags);
+
+        Map<String, String> returned = bucket.getAwsGeneratedTags();
+        assertThatThrownBy(() -> returned.put("aws:resource:region", "us-west-2"))
+            .isInstanceOf(UnsupportedOperationException.class);
+    }
+}