1. Jar files as following:
   
   com.google.cloud
   google-cloud-vertexai
   0.1.0
   

    <dependency>
        <artifactId>libraries-bom</artifactId>
        <groupId>com.google.cloud</groupId>
        <scope>import</scope>
        <type>pom</type>
        <version>26.29.0</version>
    </dependency>
   

Check the dependency:
com.google.cloud:google-cloud-vertexai:0.1.0:
com.google.api.grpc:proto-google-iam-v1:1.24.0

2. Code segment:
   @RestController
   @RequestMapping("/api/gemini")
   @slf4j
   public class GeminiChatController {

   @value("${google.credentials}")
   private Resource gcpKeyFile;

   @GetMapping("/chat")
   public void test() {
   String projectId = "gptdemo-408313";
   String location = "us-west2";
   String modelName = "gemini-pro-vision";
   try {
   String output = this.simpleQuestion(projectId, location, modelName);
   log.info("output: {}", output);
   System.out.println(output);
   }catch (Exception e) {
   System.out.println(e);}
   }

   public String simpleQuestion(String projectId, String location, String modelName)
   throws Exception {
   // Initialize client that will be used to send requests.
   // This client only needs to be created once, and can be reused for multiple requests.
   GoogleCredentials credentials = GoogleCredentials.fromStream(gcpKeyFile.getInputStream());

    try (VertexAI vertexAI = new VertexAI(projectId, location, credentials)) {
        String output;
        GenerativeModel model = new GenerativeModel(modelName, vertexAI);
   
        GenerateContentResponse response = model.generateContent("Why is the sky blue?");
        output = ResponseHandler.getText(response);
        return output;
    } catch (Exception e) {
        throw new Exception("Failed to make request", e);
    }
   

   }
   }

3. It failed with the error:
   java.lang.IllegalAccessError: class com.google.iam.v1.TestIamPermissionsRequest tried to access method 'com.google.protobuf.LazyStringArrayList com.google.protobuf.LazyStringArrayList.emptyList()' (com.google.iam.v1.TestIamPermissionsRequest and com.google.protobuf.LazyStringArrayList are in unnamed module of loader 'app')
   at com.google.iam.v1.TestIamPermissionsRequest.(TestIamPermissionsRequest.java:127) ~[proto-google-iam-v1-1.24.0.jar:1.24.0]
   at com.google.iam.v1.TestIamPermissionsRequest.(TestIamPermissionsRequest.java:918) ~[proto-google-iam-v1-1.24.0.jar:1.24.0]
   at com.google.cloud.vertexai.api.stub.GrpcPredictionServiceStub.(GrpcPredictionServiceStub.java:218) ~[google-cloud-vertexai-0.1.0.jar:0.1.0]
   at com.google.cloud.vertexai.api.stub.PredictionServiceStubSettings.createStub(PredictionServiceStubSettings.java:292) ~[google-cloud-vertexai-0.1.0.jar:0.1.0]
   at com.google.cloud.vertexai.api.PredictionServiceClient.(PredictionServiceClient.java:178) ~[google-cloud-vertexai-0.1.0.jar:0.1.0]
   at com.google.cloud.vertexai.api.PredictionServiceClient.create(PredictionServiceClient.java:160) ~[google-cloud-vertexai-0.1.0.jar:0.1.0]
   at com.google.cloud.vertexai.VertexAI.getPredictionServiceClient(VertexAI.java:151) ~[google-cloud-vertexai-0.1.0.jar:0.1.0]
   at com.google.cloud.vertexai.generativeai.preview.GenerativeModel.generateContentStream(GenerativeModel.java:698) ~[google-cloud-vertexai-0.1.0.jar:0.1.0]
   at com.google.cloud.vertexai.generativeai.preview.GenerativeModel.generateContent(GenerativeModel.java:396) ~[google-cloud-vertexai-0.1.0.jar:0.1.0]
   at com.google.cloud.vertexai.generativeai.preview.GenerativeModel.generateContent(GenerativeModel.java:320) ~[google-cloud-vertexai-0.1.0.jar:0.1.0]
   at com.google.cloud.vertexai.generativeai.preview.GenerativeModel.generateContent(GenerativeModel.java:269) ~[google-cloud-vertexai-0.1.0.jar:0.1.0]
   at com.md.gpt.controller.GeminiChatController.simpleQuestion(GeminiChatController.java:46) ~[classes/:na]
   at com.md.gpt.controller.GeminiChatController.test(GeminiChatController.java:29) ~[classes/:na]
   at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
   at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[na:na]
   at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
   at java.base/java.lang.reflect.Method.invoke(Method.java:568) ~[na:na]
   at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205) ~[spring-web-5.3.31.jar:5.3.31]
   at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:150) ~[spring-web-5.3.31.jar:5.3.31]
   at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117) ~[spring-webmvc-5.3.31.jar:5.3.31]
   at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895) ~[spring-webmvc-5.3.31.jar:5.3.31]
   at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.31.jar:5.3.31]
   at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.31.jar:5.3.31]
   at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1072) ~[spring-webmvc-5.3.31.jar:5.3.31]
   at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:965) ~[spring-webmvc-5.3.31.jar:5.3.31]
   at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.31.jar:5.3.31]
   at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.3.31.jar:5.3.31]

Could you please have a look, thanks?