Make default Chat memory repository non-static

 - Update the builder to initialize the default chatmemory respository if it isn't set by the builder method

Signed-off-by: Ilayaperumal Gopinathan <[email protected]>

Author: ilayaperumalg

spring-ai-model/src/main/java/org/springframework/ai/chat/memory/MessageWindowChatMemory.java

@@ -16,15 +16,15 @@
 
 package org.springframework.ai.chat.memory;
 
-import org.springframework.ai.chat.messages.Message;
-import org.springframework.ai.chat.messages.SystemMessage;
-import org.springframework.util.Assert;
-
 import java.util.ArrayList;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
 
+import org.springframework.ai.chat.messages.Message;
+import org.springframework.ai.chat.messages.SystemMessage;
+import org.springframework.util.Assert;
+
 /**
  * A chat memory implementation that maintains a message window of a specified size,
  * ensuring that the total number of messages does not exceed the specified limit. When
@@ -36,14 +36,13 @@
  * {@link SystemMessage} messages are preserved while evicting other types of messages.
  *
  * @author Thomas Vitale
+ * @author Ilayaperumal Gopinathan
  * @since 1.0.0
  */
 public final class MessageWindowChatMemory implements ChatMemory {
 
 	private static final int DEFAULT_MAX_MESSAGES = 20;
 
-	private static final ChatMemoryRepository DEFAULT_CHAT_MEMORY_REPOSITORY = new InMemoryChatMemoryRepository();
-
 	private final ChatMemoryRepository chatMemoryRepository;
 
 	private final int maxMessages;
@@ -124,7 +123,7 @@ public static Builder builder() {
 
 	public static class Builder {
 
-		private ChatMemoryRepository chatMemoryRepository = DEFAULT_CHAT_MEMORY_REPOSITORY;
+		private ChatMemoryRepository chatMemoryRepository;
 
 		private int maxMessages = DEFAULT_MAX_MESSAGES;
 
@@ -142,7 +141,10 @@ public Builder maxMessages(int maxMessages) {
 		}
 
 		public MessageWindowChatMemory build() {
-			return new MessageWindowChatMemory(chatMemoryRepository, maxMessages);
+			if (this.chatMemoryRepository == null) {
+				this.chatMemoryRepository = new InMemoryChatMemoryRepository();
+			}
+			return new MessageWindowChatMemory(this.chatMemoryRepository, this.maxMessages);
 		}
 
 	}