Made DefaultSdkAutoConstructList and DefaultSdkAutoConstructMap serializable, added serialVersionUID (#5938)

Author: roamariei

.changes/next-release/feature-AWSSDKforJavav2-54bedb6.json

@@ -0,0 +1,6 @@
+{
+    "type": "feature",
+    "category": "AWS SDK for Java v2",
+    "contributor": "",
+    "description": "Made DefaultSdkAutoConstructList and DefaultSdkAutoConstructMap serializable"
+}

core/sdk-core/src/main/java/software/amazon/awssdk/core/util/DefaultSdkAutoConstructList.java

@@ -15,6 +15,7 @@
 
 package software.amazon.awssdk.core.util;
 
+import java.io.Serializable;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Iterator;
@@ -30,9 +31,11 @@
  * @param <T> The element type.
  */
 @SdkProtectedApi
-public final class DefaultSdkAutoConstructList<T> implements SdkAutoConstructList<T> {
+public final class DefaultSdkAutoConstructList<T> implements SdkAutoConstructList<T>, Serializable {
     private static final DefaultSdkAutoConstructList INSTANCE = new DefaultSdkAutoConstructList();
 
+    private static final long serialVersionUID = 1L;
+
     private final List impl = Collections.emptyList();
 
     private DefaultSdkAutoConstructList() {
@@ -173,4 +176,7 @@ public String toString() {
         return impl.toString();
     }
 
+    private Object readResolve() {
+        return getInstance();
+    }
 }

core/sdk-core/src/main/java/software/amazon/awssdk/core/util/DefaultSdkAutoConstructMap.java

@@ -15,6 +15,7 @@
 
 package software.amazon.awssdk.core.util;
 
+import java.io.Serializable;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Map;
@@ -30,9 +31,11 @@
  * @param <V> The value type.
  */
 @SdkProtectedApi
-public final class DefaultSdkAutoConstructMap<K, V> implements SdkAutoConstructMap<K, V> {
+public final class DefaultSdkAutoConstructMap<K, V> implements SdkAutoConstructMap<K, V>, Serializable {
     private static final DefaultSdkAutoConstructMap INSTANCE = new DefaultSdkAutoConstructMap();
 
+    private static final long serialVersionUID = 1L;
+
     private final Map<K, V> impl = Collections.emptyMap();
 
     private DefaultSdkAutoConstructMap() {
@@ -117,4 +120,8 @@ public int hashCode() {
     public String toString() {
         return impl.toString();
     }
+
+    private Object readResolve() {
+        return getInstance();
+    }
 }

core/sdk-core/src/test/java/software/amazon/awssdk/core/util/DefaultSdkAutoConstructListTest.java

@@ -16,7 +16,13 @@
 package software.amazon.awssdk.core.util;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertSame;
 
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
 import java.util.LinkedList;
 import org.junit.jupiter.api.Test;
 
@@ -42,4 +48,25 @@ public void hashCode_sameAsEmptyList() {
     public void toString_emptyList() {
         assertThat(INSTANCE.toString()).isEqualTo("[]");
     }
+
+    @Test
+    public void serialization_sameSingletonInstance() throws Exception {
+        DefaultSdkAutoConstructList<?> originalInstance = DefaultSdkAutoConstructList.getInstance();
+
+        // Serialize the object
+        ByteArrayOutputStream byteOut = new ByteArrayOutputStream();
+        ObjectOutputStream objectOut = new ObjectOutputStream(byteOut);
+        objectOut.writeObject(originalInstance);
+        objectOut.close();
+
+        // Deserialize the object
+        ByteArrayInputStream byteIn = new ByteArrayInputStream(byteOut.toByteArray());
+        ObjectInputStream objectIn = new ObjectInputStream(byteIn);
+        DefaultSdkAutoConstructList<?> deserializedInstance = (DefaultSdkAutoConstructList<?>) objectIn.readObject();
+        objectIn.close();
+
+        // Assert that deserialization was successful
+        assertNotNull(deserializedInstance);
+        assertSame(originalInstance, deserializedInstance, "Deserialized instance should be the same singleton instance");
+    }
 }

core/sdk-core/src/test/java/software/amazon/awssdk/core/util/DefaultSdkAutoConstructMapTest.java

@@ -16,7 +16,13 @@
 package software.amazon.awssdk.core.util;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertSame;
 
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
 import java.util.HashMap;
 import org.junit.jupiter.api.Test;
 
@@ -41,4 +47,25 @@ public void hashCode_sameAsEmptyMap() {
     public void toString_emptyMap() {
         assertThat(AUTO_CONSTRUCT_MAP.toString()).isEqualTo("{}");
     }
+
+    @Test
+    public void serialization_sameSingletonInstance() throws Exception {
+        DefaultSdkAutoConstructMap<?, ?> originalInstance = DefaultSdkAutoConstructMap.getInstance();
+
+        // Serialize the object
+        ByteArrayOutputStream byteOut = new ByteArrayOutputStream();
+        ObjectOutputStream objectOut = new ObjectOutputStream(byteOut);
+        objectOut.writeObject(originalInstance);
+        objectOut.close();
+
+        // Deserialize the object
+        ByteArrayInputStream byteIn = new ByteArrayInputStream(byteOut.toByteArray());
+        ObjectInputStream objectIn = new ObjectInputStream(byteIn);
+        DefaultSdkAutoConstructMap<?, ?> deserializedInstance = (DefaultSdkAutoConstructMap<?, ?>) objectIn.readObject();
+        objectIn.close();
+
+        // Assert that deserialization was successful
+        assertNotNull(deserializedInstance);
+        assertSame(originalInstance, deserializedInstance, "Deserialized instance should be the same singleton instance");
+    }
 }