Added a Developer message, as used by OpenAI replacing the system mes…

…sage. Signed-off-by: Peter Dolukhanov <peter@decoded.consulting>

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

@@ -0,0 +1,127 @@
+/*
+ * 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.springframework.core.io.Resource;
+import org.springframework.lang.NonNull;
+import org.springframework.lang.Nullable;
+import org.springframework.util.StringUtils;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+
+/**
+ * A message of the type 'developer' passed as input. The developer message gives
+ * instructions or requests from developers using the API. This role typically provides
+ * detailed instructions for the model to follow, such as specific actions or formats.
+ */
+public class DeveloperMessage extends AbstractMessage {
+
+public DeveloperMessage(String textContent) {
+this(textContent, Map.of());
+}
+
+public DeveloperMessage(Resource resource) {
+this(MessageUtils.readResource(resource), Map.of());
+}
+
+private DeveloperMessage(String textContent, Map<String, Object> metadata) {
+super(MessageType.DEVELOPER, textContent, metadata);
+}
+
+@Override
+@NonNull
+public String getText() {
+return this.textContent;
+}
+
+@Override
+public boolean equals(Object o) {
+if (this == o) {
+return true;
+}
+if (!(o instanceof DeveloperMessage that)) {
+return false;
+}
+if (!super.equals(o)) {
+return false;
+}
+return Objects.equals(this.textContent, that.textContent);
+}
+
+@Override
+public int hashCode() {
+return Objects.hash(super.hashCode(), this.textContent);
+}
+
+@Override
+public String toString() {
+return "DeveloperMessage{" + "textContent='" + this.textContent + '\'' + ", messageType=" + this.messageType
++ ", metadata=" + this.metadata + '}';
+}
+
+public DeveloperMessage copy() {
+return new DeveloperMessage(getText(), Map.copyOf(this.metadata));
+}
+
+public Builder mutate() {
+return new Builder().text(this.textContent).metadata(this.metadata);
+}
+
+public static Builder builder() {
+return new Builder();
+}
+
+public static class Builder {
+
+@Nullable
+private String textContent;
+
+@Nullable
+private Resource resource;
+
+private Map<String, Object> metadata = new HashMap<>();
+
+public Builder text(String textContent) {
+this.textContent = textContent;
+return this;
+}
+
+public Builder text(Resource resource) {
+this.resource = resource;
+return this;
+}
+
+public Builder metadata(Map<String, Object> metadata) {
+this.metadata = metadata;
+return this;
+}
+
+public DeveloperMessage build() {
+if (StringUtils.hasText(textContent) && resource != null) {
+throw new IllegalArgumentException("textContent and resource cannot be set at the same time");
+}
+else if (resource != null) {
+this.textContent = MessageUtils.readResource(resource);
+}
+return new DeveloperMessage(this.textContent, this.metadata);
+}
+
+}
+
+}

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

@@ -44,6 +44,13 @@ public enum MessageType {
  */
 SYSTEM("system"),
 
+/**
+ * A {@link Message} of type {@literal developer} passed as input {@link Message}
+ * Messages containing instructions or requests from developers using the API.
+ * @see DeveloperMessage
+ */
+DEVELOPER("developer"),
+
 /**
  * A {@link Message} of type {@literal function} passed as input {@link Message
  * Messages} with function content in a chat application.