Add URL context option to Google GenAI chat

[nuheajiohc]

Summary

This PR adds an option to enable the Gemini URL Context tool in GoogleGenAiChatModel via GoogleGenAiChatOptions.

• Introduce urlContextEnabled flag in GoogleGenAiChatOptions (default: false).
• When the flag is true, the generated Gemini request includes the UrlContext tool.
• Update builder/copy/equals/hashCode/toString to handle the new option.
• Add tests to verify option copying/equality and request generation with the URL Context tool.

Background

Gemini provides a URL Context tool that allows the model to ground its answers in the content of a given URL (e.g. blog posts, documentation pages, articles, etc.).
Gemini API - Tools [Url Context]

The Google Java SDK already allows this:

Client client = new Client();

String prompt = "'https://www.example-article.com', Who is the author of this article?";

GenerateContentConfig config = GenerateContentConfig.builder()
    .tools(List.of(
        Tool.builder()
            .urlContext(UrlContext.builder().build())
            .build()
    ))
    .build();

GenerateContentResponse response =
    client.models.generateContent(
        "gemini-2.5-flash",
        prompt,
        config
    );

System.out.println(response.text());

However, Spring AI’s GoogleGenAiChatModel does not currently expose a simple way to enable this feature through GoogleGenAiChatOptions.

Changes

• GoogleGenAiChatOptions

  • Add private Boolean urlContextEnabled
  • Extend builder with urlContextEnabled(Boolean urlContextEnabled)
  • Include field in copy/from, equals, hashCode, toString

• GoogleGenAiChatModel

  • Add UrlContext tool when urlContextEnabled == Boolean.TRUE
  • Keep default behavior unchanged when disabled

• Tests

  • Validate option propagation
  • Validate equals / hashCode
  • Validate request contains or excludes UrlContext

Example usage

String apiKey = System.getenv("GEMINI_API_KEY"); // Set your API key as an environment variable

GoogleGenAiChatModel chatModel = GoogleGenAiChatModel.builder()
			.genAiClient(Client.builder().apiKey(apiKey).build())
			.defaultOptions(GoogleGenAiChatOptions.builder().model(GoogleGenAiChatModel.ChatModel.GEMINI_2_5_FLASH).build())
			.build();

ChatClient chatClient = ChatClient.builder(chatModel).build();

GoogleGenAiChatOptions options = GoogleGenAiChatOptions.builder()
    .urlContextEnabled(true)
    .build();

String prompt = "'https://www.example-article.com', Who is the author of this article?";

String answer = chatClient
    .prompt(prompt)
    .options(options)
    .call()
    .content();