fix: add media/image support in Spring AI MessageConverter

Previously, MessageConverter only transferred text content from ADK to Spring AI,
ignoring image and media attachments. This caused vision model requests to fail
even though Spring AI's underlying models (like GPT-4o) support image inputs.

Updated MessageConverter to properly handle image/media parts by constructing
UserMessage with Media attachments.

Fixes #705

Author: prasadskarmarkar

contrib/spring-ai/src/main/java/com/google/adk/models/springai/MessageConverter.java

@@ -243,11 +243,7 @@ private List<Message> handleUserContent(Content content) {
     }
 
     List<Message> messages = new ArrayList<>();
-    // Create UserMessage with text
-    // TODO: Media attachments support - UserMessage constructors with media are private in Spring
-    // AI 1.1.0
-    // For now, only text content is supported
-    messages.add(new UserMessage(textBuilder.toString()));
+    messages.add(UserMessage.builder().text(textBuilder.toString()).media(mediaList).build());
     messages.addAll(toolResponseMessages);
 
     return messages;

contrib/spring-ai/src/test/java/com/google/adk/models/springai/MessageConverterTest.java

@@ -60,7 +60,9 @@ void testToLlmPromptWithUserMessage() {
     assertThat(prompt.getInstructions()).hasSize(1);
     Message message = prompt.getInstructions().get(0);
     assertThat(message).isInstanceOf(UserMessage.class);
-    assertThat(((UserMessage) message).getText()).isEqualTo("Hello, how are you?");
+    UserMessage userMessage = (UserMessage) message;
+    assertThat(userMessage.getText()).isEqualTo("Hello, how are you?");
+    assertThat(userMessage.getMedia()).isEmpty();
   }
 
   @Test
@@ -444,4 +446,149 @@ void testCombineMultipleSystemMessagesForGeminiCompatibility() {
     assertThat(secondMessage).isInstanceOf(UserMessage.class);
     assertThat(((UserMessage) secondMessage).getText()).isEqualTo("Hello world");
   }
+
+  @Test
+  void testUserMessageWithInlineMediaData() {
+    // Test conversion of ADK Content with inline media (image bytes) to Spring AI UserMessage
+    byte[] imageData = "fake-image-data".getBytes();
+    String mimeType = "image/png";
+
+    Content userContent =
+        Content.builder()
+            .role("user")
+            .parts(
+                List.of(
+                    Part.fromText("What's in this image?"),
+                    Part.builder()
+                        .inlineData(
+                            com.google.genai.types.Blob.builder()
+                                .mimeType(mimeType)
+                                .data(imageData)
+                                .build())
+                        .build()))
+            .build();
+
+    LlmRequest request = LlmRequest.builder().contents(List.of(userContent)).build();
+
+    Prompt prompt = messageConverter.toLlmPrompt(request);
+
+    assertThat(prompt.getInstructions()).hasSize(1);
+    Message message = prompt.getInstructions().get(0);
+    assertThat(message).isInstanceOf(UserMessage.class);
+
+    UserMessage userMessage = (UserMessage) message;
+    assertThat(userMessage.getText()).isEqualTo("What's in this image?");
+    assertThat(userMessage.getMedia()).hasSize(1);
+    org.springframework.ai.content.Media media = userMessage.getMedia().get(0);
+    assertThat(media.getMimeType().toString()).isEqualTo(mimeType);
+    assertThat(media.getData()).isInstanceOf(byte[].class);
+    byte[] actualData = (byte[]) media.getData();
+    assertThat(actualData).isEqualTo(imageData);
+  }
+
+  @Test
+  void testUserMessageWithFileMediaData() {
+    // Test conversion of ADK Content with file-based media (URI) to Spring AI UserMessage
+    String fileUri = "gs://bucket/image.jpg";
+    String mimeType = "image/jpeg";
+
+    Content userContent =
+        Content.builder()
+            .role("user")
+            .parts(
+                List.of(
+                    Part.fromText("Analyze this image"),
+                    Part.builder()
+                        .fileData(
+                            com.google.genai.types.FileData.builder()
+                                .mimeType(mimeType)
+                                .fileUri(fileUri)
+                                .build())
+                        .build()))
+            .build();
+
+    LlmRequest request = LlmRequest.builder().contents(List.of(userContent)).build();
+
+    Prompt prompt = messageConverter.toLlmPrompt(request);
+
+    assertThat(prompt.getInstructions()).hasSize(1);
+    Message message = prompt.getInstructions().get(0);
+    assertThat(message).isInstanceOf(UserMessage.class);
+
+    UserMessage userMessage = (UserMessage) message;
+    assertThat(userMessage.getText()).isEqualTo("Analyze this image");
+    assertThat(userMessage.getMedia()).hasSize(1);
+    org.springframework.ai.content.Media media = userMessage.getMedia().get(0);
+    assertThat(media.getMimeType().toString()).isEqualTo(mimeType);
+    assertThat(media.getData()).isInstanceOf(String.class);
+    String actualUri = (String) media.getData();
+    assertThat(actualUri).isEqualTo(fileUri);
+  }
+
+  @Test
+  void testUserMessageWithMultipleMediaAttachments() {
+    // Test conversion with multiple media attachments
+    byte[] image1 = "image1-data".getBytes();
+    byte[] image2 = "image2-data".getBytes();
+
+    Content userContent =
+        Content.builder()
+            .role("user")
+            .parts(
+                List.of(
+                    Part.fromText("Compare these images"),
+                    Part.builder()
+                        .inlineData(
+                            com.google.genai.types.Blob.builder()
+                                .mimeType("image/png")
+                                .data(image1)
+                                .build())
+                        .build(),
+                    Part.builder()
+                        .inlineData(
+                            com.google.genai.types.Blob.builder()
+                                .mimeType("image/jpeg")
+                                .data(image2)
+                                .build())
+                        .build()))
+            .build();
+
+    LlmRequest request = LlmRequest.builder().contents(List.of(userContent)).build();
+
+    Prompt prompt = messageConverter.toLlmPrompt(request);
+
+    assertThat(prompt.getInstructions()).hasSize(1);
+    UserMessage userMessage = (UserMessage) prompt.getInstructions().get(0);
+    assertThat(userMessage.getText()).isEqualTo("Compare these images");
+    assertThat(userMessage.getMedia()).hasSize(2);
+  }
+
+  @Test
+  void testUserMessageWithMediaOnly() {
+    // Test conversion with media but no text
+    byte[] imageData = "image-only".getBytes();
+
+    Content userContent =
+        Content.builder()
+            .role("user")
+            .parts(
+                List.of(
+                    Part.builder()
+                        .inlineData(
+                            com.google.genai.types.Blob.builder()
+                                .mimeType("image/png")
+                                .data(imageData)
+                                .build())
+                        .build()))
+            .build();
+
+    LlmRequest request = LlmRequest.builder().contents(List.of(userContent)).build();
+
+    Prompt prompt = messageConverter.toLlmPrompt(request);
+
+    assertThat(prompt.getInstructions()).hasSize(1);
+    UserMessage userMessage = (UserMessage) prompt.getInstructions().get(0);
+    assertThat(userMessage.getText()).isEmpty();
+    assertThat(userMessage.getMedia()).hasSize(1);
+  }
 }