feat: Add builder for AssistantMessage

spring-ai-model/src/main/java/org/springframework/ai/chat/messages/AssistantMessage.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2023-2024 the original author or authors.
+ * Copyright 2023-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -33,6 +33,7 @@
  *
  * @author Mark Pollack
  * @author Christian Tzolov
+ * @author Thomas Vitale
  * @since 1.0.0
  */
 public class AssistantMessage extends AbstractMessage implements MediaContent {
@@ -45,14 +46,26 @@ public AssistantMessage(String content) {
 		this(content, Map.of());
 	}
 
+	/**
+	 * @deprecated in favor of {@link AssistantMessage#builder()}.
+	 */
+	@Deprecated
 	public AssistantMessage(String content, Map<String, Object> properties) {
 		this(content, properties, List.of());
 	}
 
+	/**
+	 * @deprecated in favor of {@link AssistantMessage#builder()}.
+	 */
+	@Deprecated
 	public AssistantMessage(String content, Map<String, Object> properties, List<ToolCall> toolCalls) {
 		this(content, properties, toolCalls, List.of());
 	}
 
+	/**
+	 * @deprecated in favor of {@link AssistantMessage#builder()}.
+	 */
+	@Deprecated
 	public AssistantMessage(String content, Map<String, Object> properties, List<ToolCall> toolCalls,
 			List<Media> media) {
 		super(MessageType.ASSISTANT, content, properties);
@@ -100,8 +113,51 @@ public String toString() {
 				+ this.textContent + ", metadata=" + this.metadata + "]";
 	}
 
+	public static Builder builder() {
+		return new Builder();
+	}
+
 	public record ToolCall(String id, String type, String name, String arguments) {
 
 	}
 
+	public static final class Builder {
+
+		private String content;
+
+		private Map<String, Object> properties = Map.of();
+
+		private List<ToolCall> toolCalls = List.of();
+
+		private List<Media> media = List.of();
+
+		private Builder() {
+		}
+
+		public Builder content(String content) {
+			this.content = content;
+			return this;
+		}
+
+		public Builder properties(Map<String, Object> properties) {
+			this.properties = properties;
+			return this;
+		}
+
+		public Builder toolCalls(List<ToolCall> toolCalls) {
+			this.toolCalls = toolCalls;
+			return this;
+		}
+
+		public Builder media(List<Media> media) {
+			this.media = media;
+			return this;
+		}
+
+		public AssistantMessage build() {
+			return new AssistantMessage(this.content, this.properties, this.toolCalls, this.media);
+		}
+
+	}
+
 }

spring-ai-model/src/test/java/org/springframework/ai/chat/messages/AssistantMessageTests.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2023-2025 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License 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 org.springframework.ai.chat.messages;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+/**
+ * Unit tests for {@link AssistantMessage}.
+ *
+ * @author Thomas Vitale
+ */
+class AssistantMessageTests {
+
+	@Test
+	void whenMediaIsNullThenThrow() {
+		assertThatThrownBy(() -> AssistantMessage.builder().media(null).build())
+			.isInstanceOf(IllegalArgumentException.class)
+			.hasMessageContaining("Media must not be null");
+	}
+
+	@Test
+	void whenMetadataIsNullThenThrow() {
+		assertThatThrownBy(() -> AssistantMessage.builder().properties(null).build())
+			.isInstanceOf(IllegalArgumentException.class)
+			.hasMessageContaining("Metadata must not be null");
+	}
+
+	@Test
+	void whenToolCallsIsNullThenThrow() {
+		assertThatThrownBy(() -> AssistantMessage.builder().toolCalls(null).build())
+			.isInstanceOf(IllegalArgumentException.class)
+			.hasMessageContaining("Tool calls must not be null");
+	}
+
+}