Generate content using Vertex AI Express Mode

This sample utilizes Vertex AI Express Mode to generate text content.

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For detailed documentation that includes this code sample, see the following:

Code sample

Go

Before trying this sample, follow the Go setup instructions in the Vertex AI quickstart using client libraries . For more information, see the Vertex AI Go API reference documentation .

To authenticate to Vertex AI, set up Application Default Credentials. For more information, see Set up authentication for a local development environment .

  import 
  
 ( 
  
 "context" 
  
 "fmt" 
  
 "io" 
  
 "google.golang.org/genai" 
 ) 
 var 
  
 newClient 
  
 = 
  
 genai 
 . 
 NewClient 
 // generateContent shows how to use Vertex AI Express mode with an API key. 
 func 
  
 generateContentWithApiKey 
 ( 
 w 
  
 io 
 . 
 Writer 
 ) 
  
 error 
  
 { 
  
 ctx 
  
 := 
  
 context 
 . 
 Background 
 () 
  
 // TODO(developer): Replace with your actual API key 
  
 apiKey 
  
 := 
  
 "YOUR_API_KEY" 
  
 client 
 , 
  
 err 
  
 := 
  
 newClient 
 ( 
 ctx 
 , 
  
& genai 
 . 
 ClientConfig 
 { 
  
 APIKey 
 : 
  
 apiKey 
 , 
  
 HTTPOptions 
 : 
  
 genai 
 . 
 HTTPOptions 
 { 
 APIVersion 
 : 
  
 "v1" 
 }, 
  
 }) 
  
 if 
  
 err 
  
 != 
  
 nil 
  
 { 
  
 return 
  
 fmt 
 . 
 Errorf 
 ( 
 "failed to create genai client: %w" 
 , 
  
 err 
 ) 
  
 } 
  
 modelName 
  
 := 
  
 "gemini-2.5-flash" 
  
 resp 
 , 
  
 err 
  
 := 
  
 client 
 . 
 Models 
 . 
 GenerateContent 
 ( 
 ctx 
 , 
  
 modelName 
 , 
  
 [] 
 * 
 genai 
 . 
 Content 
 { 
  
 { 
 Parts 
 : 
  
 [] 
 * 
 genai 
 . 
 Part 
 { 
  
 { 
 Text 
 : 
  
 "Explain bubble sort to me." 
 }, 
  
 }, 
  
 Role 
 : 
  
 genai 
 . 
 RoleUser 
 }, 
  
 }, 
  
 nil 
 , 
  
 ) 
  
 if 
  
 err 
  
 != 
  
 nil 
  
 { 
  
 return 
  
 fmt 
 . 
 Errorf 
 ( 
 "failed to generate content: %w" 
 , 
  
 err 
 ) 
  
 } 
  
 fmt 
 . 
 Fprintln 
 ( 
 w 
 , 
  
 resp 
 . 
 Text 
 ()) 
  
 // Example response: 
  
 // Bubble Sort is a simple sorting algorithm that repeatedly steps through the list 
  
 return 
  
 nil 
 }

Java

Before trying this sample, follow the Java setup instructions in the Vertex AI quickstart using client libraries . For more information, see the Vertex AI Java API reference documentation .

To authenticate to Vertex AI, set up Application Default Credentials. For more information, see Set up authentication for a local development environment .

  import 
  
 com.google.genai.Client 
 ; 
 import 
  
 com.google.genai.types.GenerateContentConfig 
 ; 
 import 
  
 com.google.genai.types.GenerateContentResponse 
 ; 
 public 
  
 class 
 ExpressModeWithApiKey 
  
 { 
  
 public 
  
 static 
  
 void 
  
 main 
 ( 
 String 
 [] 
  
 args 
 ) 
  
 { 
  
 // TODO(developer): Replace these variables before running the sample. 
  
 String 
  
 modelId 
  
 = 
  
 "gemini-2.5-flash" 
 ; 
  
 String 
  
 apiKey 
  
 = 
  
 "YOUR_API_KEY" 
 ; 
  
 generateContent 
 ( 
 modelId 
 , 
  
 apiKey 
 ); 
  
 } 
  
 // Generates content with Vertex AI Api key. 
  
 public 
  
 static 
  
 String 
  
 generateContent 
 ( 
 String 
  
 modelId 
 , 
  
 String 
  
 apiKey 
 ) 
  
 { 
  
 // Client Initialization. Once created, it can be reused for multiple requests. 
  
 try 
  
 ( 
 Client 
  
 client 
  
 = 
  
 Client 
 . 
 builder 
 (). 
 apiKey 
 ( 
 apiKey 
 ). 
 vertexAI 
 ( 
 true 
 ). 
 build 
 ()) 
  
 { 
  
 GenerateContentResponse 
  
 response 
  
 = 
  
 client 
 . 
 models 
 . 
 generateContent 
 ( 
  
 modelId 
 , 
  
 "Explain bubble sort to me." 
 , 
  
 GenerateContentConfig 
 . 
 builder 
 (). 
 build 
 ()); 
  
 System 
 . 
 out 
 . 
 print 
 ( 
 response 
 . 
 text 
 ()); 
  
 // Example response: 
  
 // Bubble sort is one of the simplest sorting algorithms. It's often used to introduce the 
  
 // concept of sorting because its logic is very straightforward. 
  
 // 
  
 // Imagine you have a list of numbers that you want to put in order, like `[5, 1, 4, 2, 8]`. 
  
 // ... 
  
 return 
  
 response 
 . 
 text 
 (); 
  
 } 
  
 } 
 }

Node.js

Before trying this sample, follow the Node.js setup instructions in the Vertex AI quickstart using client libraries . For more information, see the Vertex AI Node.js API reference documentation .

To authenticate to Vertex AI, set up Application Default Credentials. For more information, see Set up authentication for a local development environment .

  const 
  
 { 
 GoogleGenAI 
 } 
  
 = 
  
 require 
 ( 
 '@google/genai' 
 ); 
 const 
  
 API_KEY 
  
 = 
  
 'YOUR_EXPRESS_MODE_API_KEY' 
 ; 
 async 
  
 function 
  
 generateWithApiKey 
 ( 
 apiKey 
  
 = 
  
 API_KEY 
 ) 
  
 { 
  
 const 
  
 client 
  
 = 
  
 new 
  
 GoogleGenAI 
 ({ 
  
 vertexai 
 : 
  
 true 
 , 
  
 apiKey 
 : 
  
 apiKey 
 , 
  
 }); 
  
 const 
  
 response 
  
 = 
  
 await 
  
 client 
 . 
 models 
 . 
 generateContentStream 
 ({ 
  
 model 
 : 
  
 'gemini-2.5-flash' 
 , 
  
 contents 
 : 
  
 'Explain bubble sort to me.' 
 , 
  
 }); 
  
 console 
 . 
 log 
 ( 
 response 
 . 
 text 
 ); 
  
 // Example response: 
  
 //  Bubble Sort is a simple sorting algorithm that repeatedly steps through the list 
  
 return 
  
 response 
 ; 
 }

Python

Before trying this sample, follow the Python setup instructions in the Vertex AI quickstart using client libraries . For more information, see the Vertex AI Python API reference documentation .

To authenticate to Vertex AI, set up Application Default Credentials. For more information, see Set up authentication for a local development environment .

  from 
  
 google 
  
 import 
 genai 
 # TODO(developer): Update below line 
 API_KEY 
 = 
 "YOUR_API_KEY" 
 client 
 = 
 genai 
 . 
 Client 
 ( 
 vertexai 
 = 
 True 
 , 
 api_key 
 = 
 API_KEY 
 ) 
 response 
 = 
 client 
 . 
 models 
 . 
 generate_content 
 ( 
 model 
 = 
 "gemini-2.5-flash" 
 , 
 contents 
 = 
 "Explain bubble sort to me." 
 , 
 ) 
 print 
 ( 
 response 
 . 
 text 
 ) 
 # Example response: 
 # Bubble Sort is a simple sorting algorithm that repeatedly steps through the list

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Explore further

Code sample

Go

Java

Node.js

Python

What's next

Generate content using Vertex AI Express Mode