├── .gitattributes
├── src
    ├── main
    │   ├── java
    │   │   └── dev
    │   │   │   └── danvega
    │   │   │       └── flash
    │   │   │           ├── GeminiModel.java
    │   │   │           ├── ModelListResponse.java
    │   │   │           ├── Application.java
    │   │   │           └── GeminiModelController.java
    │   └── resources
    │   │   └── application.properties
    └── test
    │   └── java
    │       └── dev
    │           └── danvega
    │               └── flash
    │                   └── ApplicationTests.java
├── .gitignore
├── .mvn
    └── wrapper
    │   └── maven-wrapper.properties
├── pom.xml
├── mvnw.cmd
├── README.md
└── mvnw


/.gitattributes:
--------------------------------------------------------------------------------
1 | /mvnw text eol=lf
2 | *.cmd text eol=crlf
3 | 


--------------------------------------------------------------------------------
/src/main/java/dev/danvega/flash/GeminiModel.java:
--------------------------------------------------------------------------------
1 | package dev.danvega.flash;
2 | 
3 | public record GeminiModel(String id, String object, String ownedBy) {
4 | }
5 | 


--------------------------------------------------------------------------------
/src/main/java/dev/danvega/flash/ModelListResponse.java:
--------------------------------------------------------------------------------
1 | package dev.danvega.flash;
2 | 
3 | import java.util.List;
4 | 
5 | public record ModelListResponse(String object, List<GeminiModel> data) {
6 | }
7 | 


--------------------------------------------------------------------------------
/src/test/java/dev/danvega/flash/ApplicationTests.java:
--------------------------------------------------------------------------------
 1 | package dev.danvega.flash;
 2 | 
 3 | import org.junit.jupiter.api.Test;
 4 | import org.springframework.boot.test.context.SpringBootTest;
 5 | 
 6 | @SpringBootTest
 7 | class ApplicationTests {
 8 | 
 9 | 	@Test
10 | 	void contextLoads() {
11 | 	}
12 | 
13 | }
14 | 


--------------------------------------------------------------------------------
/src/main/resources/application.properties:
--------------------------------------------------------------------------------
1 | spring.application.name=hello-flash
2 | spring.ai.openai.chat.base-url=https://generativelanguage.googleapis.com
3 | spring.ai.openai.chat.completions-path=/v1beta/openai/chat/completions
4 | spring.ai.openai.api-key=YOUR_GEMINI_API_KEY
5 | spring.ai.openai.chat.options.model=gemini-2.0-flash


--------------------------------------------------------------------------------
/.gitignore:
--------------------------------------------------------------------------------
 1 | HELP.md
 2 | target/
 3 | !.mvn/wrapper/maven-wrapper.jar
 4 | !**/src/main/**/target/
 5 | !**/src/test/**/target/
 6 | 
 7 | ### STS ###
 8 | .apt_generated
 9 | .classpath
10 | .factorypath
11 | .project
12 | .settings
13 | .springBeans
14 | .sts4-cache
15 | 
16 | ### IntelliJ IDEA ###
17 | .idea
18 | *.iws
19 | *.iml
20 | *.ipr
21 | 
22 | ### NetBeans ###
23 | /nbproject/private/
24 | /nbbuild/
25 | /dist/
26 | /nbdist/
27 | /.nb-gradle/
28 | build/
29 | !**/src/main/**/build/
30 | !**/src/test/**/build/
31 | 
32 | ### VS Code ###
33 | .vscode/
34 | 


--------------------------------------------------------------------------------
/src/main/java/dev/danvega/flash/Application.java:
--------------------------------------------------------------------------------
 1 | package dev.danvega.flash;
 2 | 
 3 | import org.springframework.ai.chat.client.ChatClient;
 4 | import org.springframework.boot.CommandLineRunner;
 5 | import org.springframework.boot.SpringApplication;
 6 | import org.springframework.boot.autoconfigure.SpringBootApplication;
 7 | import org.springframework.context.annotation.Bean;
 8 | 
 9 | @SpringBootApplication
10 | public class Application {
11 | 
12 | 	public static void main(String[] args) {
13 | 		SpringApplication.run(Application.class, args);
14 | 	}
15 | 
16 | 
17 | 	@Bean
18 | 	CommandLineRunner commandLineRunner(ChatClient .Builder builder) {
19 | 		return args -> {
20 | 		    var client = builder.build();
21 | 			var response = client.prompt("Tell me an interesting fact about Google")
22 | 					.call()
23 | 					.content();
24 | 
25 | 			System.out.println(response);
26 | 		};
27 | 	}
28 | }
29 | 


--------------------------------------------------------------------------------
/.mvn/wrapper/maven-wrapper.properties:
--------------------------------------------------------------------------------
 1 | # Licensed to the Apache Software Foundation (ASF) under one
 2 | # or more contributor license agreements.  See the NOTICE file
 3 | # distributed with this work for additional information
 4 | # regarding copyright ownership.  The ASF licenses this file
 5 | # to you under the Apache License, Version 2.0 (the
 6 | # "License"); you may not use this file except in compliance
 7 | # with the License.  You may obtain a copy of the License at
 8 | #
 9 | #   http://www.apache.org/licenses/LICENSE-2.0
10 | #
11 | # Unless required by applicable law or agreed to in writing,
12 | # software distributed under the License is distributed on an
13 | # "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
14 | # KIND, either express or implied.  See the License for the
15 | # specific language governing permissions and limitations
16 | # under the License.
17 | wrapperVersion=3.3.2
18 | distributionType=only-script
19 | distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.9.9/apache-maven-3.9.9-bin.zip
20 | 


--------------------------------------------------------------------------------
/src/main/java/dev/danvega/flash/GeminiModelController.java:
--------------------------------------------------------------------------------
 1 | package dev.danvega.flash;
 2 | 
 3 | import org.slf4j.Logger;
 4 | import org.slf4j.LoggerFactory;
 5 | import org.springframework.beans.factory.annotation.Value;
 6 | import org.springframework.core.ParameterizedTypeReference;
 7 | import org.springframework.http.HttpHeaders;
 8 | import org.springframework.http.ResponseEntity;
 9 | import org.springframework.web.bind.annotation.GetMapping;
10 | import org.springframework.web.bind.annotation.RestController;
11 | import org.springframework.web.client.RestClient;
12 | 
13 | import java.util.List;
14 | 
15 | @RestController
16 | public class GeminiModelController {
17 | 
18 |     private static final Logger log = LoggerFactory.getLogger(GeminiModelController.class);
19 |     @Value("${spring.ai.openai.api-key}")
20 |     private String GEMINI_API_KEY;
21 |     private final RestClient restClient;
22 | 
23 |     public GeminiModelController(RestClient.Builder builder) {
24 |         log.info("GeminiModelController...");
25 |         this.restClient = builder
26 |                 .baseUrl("https://generativelanguage.googleapis.com")
27 |                 .build();
28 |     }
29 | 
30 |     /*
31 |         curl https://generativelanguage.googleapis.com/v1beta/openai/models \                                                                                                                                                                                                  ✔  10s   base 
32 |         -H "Authorization: Bearer GEMINI_API_KEY"
33 |      */
34 |     @GetMapping("/models")
35 |     public List<GeminiModel> models() {
36 |         ResponseEntity<ModelListResponse> response = restClient.get()
37 |                 .uri("/v1beta/openai/models")
38 |                 .header("Authorization","Bearer " + GEMINI_API_KEY)
39 |                 .retrieve()
40 |                 .toEntity(ModelListResponse.class);
41 |         return response.getBody().data();
42 |     }
43 | 
44 | }
45 | 


--------------------------------------------------------------------------------
/pom.xml:
--------------------------------------------------------------------------------
 1 | <?xml version="1.0" encoding="UTF-8"?>
 2 | <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 3 | 	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
 4 | 	<modelVersion>4.0.0</modelVersion>
 5 | 	<parent>
 6 | 		<groupId>org.springframework.boot</groupId>
 7 | 		<artifactId>spring-boot-starter-parent</artifactId>
 8 | 		<version>3.4.3</version>
 9 | 		<relativePath/> <!-- lookup parent from repository -->
10 | 	</parent>
11 | 	<groupId>dev.danvega</groupId>
12 | 	<artifactId>hello-flash</artifactId>
13 | 	<version>0.0.1-SNAPSHOT</version>
14 | 	<name>hello-flash</name>
15 | 	<description>Demo project for Spring Boot</description>
16 | 	<url/>
17 | 	<licenses>
18 | 		<license/>
19 | 	</licenses>
20 | 	<developers>
21 | 		<developer/>
22 | 	</developers>
23 | 	<scm>
24 | 		<connection/>
25 | 		<developerConnection/>
26 | 		<tag/>
27 | 		<url/>
28 | 	</scm>
29 | 	<properties>
30 | 		<java.version>23</java.version>
31 | 		<spring-ai.version>1.0.0-M6</spring-ai.version>
32 | 	</properties>
33 | 	<dependencies>
34 | 		<dependency>
35 | 			<groupId>org.springframework.boot</groupId>
36 | 			<artifactId>spring-boot-starter-web</artifactId>
37 | 		</dependency>
38 | 		<dependency>
39 | 			<groupId>org.springframework.ai</groupId>
40 | 			<artifactId>spring-ai-openai-spring-boot-starter</artifactId>
41 | 		</dependency>
42 | 
43 | 		<dependency>
44 | 			<groupId>org.springframework.boot</groupId>
45 | 			<artifactId>spring-boot-starter-test</artifactId>
46 | 			<scope>test</scope>
47 | 		</dependency>
48 | 	</dependencies>
49 | 	<dependencyManagement>
50 | 		<dependencies>
51 | 			<dependency>
52 | 				<groupId>org.springframework.ai</groupId>
53 | 				<artifactId>spring-ai-bom</artifactId>
54 | 				<version>${spring-ai.version}</version>
55 | 				<type>pom</type>
56 | 				<scope>import</scope>
57 | 			</dependency>
58 | 		</dependencies>
59 | 	</dependencyManagement>
60 | 
61 | 	<build>
62 | 		<plugins>
63 | 			<plugin>
64 | 				<groupId>org.springframework.boot</groupId>
65 | 				<artifactId>spring-boot-maven-plugin</artifactId>
66 | 			</plugin>
67 | 		</plugins>
68 | 	</build>
69 | 
70 | </project>
71 | 


--------------------------------------------------------------------------------
/mvnw.cmd:
--------------------------------------------------------------------------------
  1 | <# : batch portion
  2 | @REM ----------------------------------------------------------------------------
  3 | @REM Licensed to the Apache Software Foundation (ASF) under one
  4 | @REM or more contributor license agreements.  See the NOTICE file
  5 | @REM distributed with this work for additional information
  6 | @REM regarding copyright ownership.  The ASF licenses this file
  7 | @REM to you under the Apache License, Version 2.0 (the
  8 | @REM "License"); you may not use this file except in compliance
  9 | @REM with the License.  You may obtain a copy of the License at
 10 | @REM
 11 | @REM    http://www.apache.org/licenses/LICENSE-2.0
 12 | @REM
 13 | @REM Unless required by applicable law or agreed to in writing,
 14 | @REM software distributed under the License is distributed on an
 15 | @REM "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 16 | @REM KIND, either express or implied.  See the License for the
 17 | @REM specific language governing permissions and limitations
 18 | @REM under the License.
 19 | @REM ----------------------------------------------------------------------------
 20 | 
 21 | @REM ----------------------------------------------------------------------------
 22 | @REM Apache Maven Wrapper startup batch script, version 3.3.2
 23 | @REM
 24 | @REM Optional ENV vars
 25 | @REM   MVNW_REPOURL - repo url base for downloading maven distribution
 26 | @REM   MVNW_USERNAME/MVNW_PASSWORD - user and password for downloading maven
 27 | @REM   MVNW_VERBOSE - true: enable verbose log; others: silence the output
 28 | @REM ----------------------------------------------------------------------------
 29 | 
 30 | @IF "%__MVNW_ARG0_NAME__%"=="" (SET __MVNW_ARG0_NAME__=%~nx0)
 31 | @SET __MVNW_CMD__=
 32 | @SET __MVNW_ERROR__=
 33 | @SET __MVNW_PSMODULEP_SAVE=%PSModulePath%
 34 | @SET PSModulePath=
 35 | @FOR /F "usebackq tokens=1* delims==" %%A IN (`powershell -noprofile "& {$scriptDir='%~dp0'; $script='%__MVNW_ARG0_NAME__%'; icm -ScriptBlock ([Scriptblock]::Create((Get-Content -Raw '%~f0'))) -NoNewScope}"`) DO @(
 36 |   IF "%%A"=="MVN_CMD" (set __MVNW_CMD__=%%B) ELSE IF "%%B"=="" (echo %%A) ELSE (echo %%A=%%B)
 37 | )
 38 | @SET PSModulePath=%__MVNW_PSMODULEP_SAVE%
 39 | @SET __MVNW_PSMODULEP_SAVE=
 40 | @SET __MVNW_ARG0_NAME__=
 41 | @SET MVNW_USERNAME=
 42 | @SET MVNW_PASSWORD=
 43 | @IF NOT "%__MVNW_CMD__%"=="" (%__MVNW_CMD__% %*)
 44 | @echo Cannot start maven from wrapper >&2 && exit /b 1
 45 | @GOTO :EOF
 46 | : end batch / begin powershell #>
 47 | 
 48 | $ErrorActionPreference = "Stop"
 49 | if ($env:MVNW_VERBOSE -eq "true") {
 50 |   $VerbosePreference = "Continue"
 51 | }
 52 | 
 53 | # calculate distributionUrl, requires .mvn/wrapper/maven-wrapper.properties
 54 | $distributionUrl = (Get-Content -Raw "$scriptDir/.mvn/wrapper/maven-wrapper.properties" | ConvertFrom-StringData).distributionUrl
 55 | if (!$distributionUrl) {
 56 |   Write-Error "cannot read distributionUrl property in $scriptDir/.mvn/wrapper/maven-wrapper.properties"
 57 | }
 58 | 
 59 | switch -wildcard -casesensitive ( $($distributionUrl -replace '^.*/','') ) {
 60 |   "maven-mvnd-*" {
 61 |     $USE_MVND = $true
 62 |     $distributionUrl = $distributionUrl -replace '-bin\.[^.]*$',"-windows-amd64.zip"
 63 |     $MVN_CMD = "mvnd.cmd"
 64 |     break
 65 |   }
 66 |   default {
 67 |     $USE_MVND = $false
 68 |     $MVN_CMD = $script -replace '^mvnw','mvn'
 69 |     break
 70 |   }
 71 | }
 72 | 
 73 | # apply MVNW_REPOURL and calculate MAVEN_HOME
 74 | # maven home pattern: ~/.m2/wrapper/dists/{apache-maven-<version>,maven-mvnd-<version>-<platform>}/<hash>
 75 | if ($env:MVNW_REPOURL) {
 76 |   $MVNW_REPO_PATTERN = if ($USE_MVND) { "/org/apache/maven/" } else { "/maven/mvnd/" }
 77 |   $distributionUrl = "$env:MVNW_REPOURL$MVNW_REPO_PATTERN$($distributionUrl -replace '^.*'+$MVNW_REPO_PATTERN,'')"
 78 | }
 79 | $distributionUrlName = $distributionUrl -replace '^.*/',''
 80 | $distributionUrlNameMain = $distributionUrlName -replace '\.[^.]*$','' -replace '-bin$',''
 81 | $MAVEN_HOME_PARENT = "$HOME/.m2/wrapper/dists/$distributionUrlNameMain"
 82 | if ($env:MAVEN_USER_HOME) {
 83 |   $MAVEN_HOME_PARENT = "$env:MAVEN_USER_HOME/wrapper/dists/$distributionUrlNameMain"
 84 | }
 85 | $MAVEN_HOME_NAME = ([System.Security.Cryptography.MD5]::Create().ComputeHash([byte[]][char[]]$distributionUrl) | ForEach-Object {$_.ToString("x2")}) -join ''
 86 | $MAVEN_HOME = "$MAVEN_HOME_PARENT/$MAVEN_HOME_NAME"
 87 | 
 88 | if (Test-Path -Path "$MAVEN_HOME" -PathType Container) {
 89 |   Write-Verbose "found existing MAVEN_HOME at $MAVEN_HOME"
 90 |   Write-Output "MVN_CMD=$MAVEN_HOME/bin/$MVN_CMD"
 91 |   exit $?
 92 | }
 93 | 
 94 | if (! $distributionUrlNameMain -or ($distributionUrlName -eq $distributionUrlNameMain)) {
 95 |   Write-Error "distributionUrl is not valid, must end with *-bin.zip, but found $distributionUrl"
 96 | }
 97 | 
 98 | # prepare tmp dir
 99 | $TMP_DOWNLOAD_DIR_HOLDER = New-TemporaryFile
100 | $TMP_DOWNLOAD_DIR = New-Item -Itemtype Directory -Path "$TMP_DOWNLOAD_DIR_HOLDER.dir"
101 | $TMP_DOWNLOAD_DIR_HOLDER.Delete() | Out-Null
102 | trap {
103 |   if ($TMP_DOWNLOAD_DIR.Exists) {
104 |     try { Remove-Item $TMP_DOWNLOAD_DIR -Recurse -Force | Out-Null }
105 |     catch { Write-Warning "Cannot remove $TMP_DOWNLOAD_DIR" }
106 |   }
107 | }
108 | 
109 | New-Item -Itemtype Directory -Path "$MAVEN_HOME_PARENT" -Force | Out-Null
110 | 
111 | # Download and Install Apache Maven
112 | Write-Verbose "Couldn't find MAVEN_HOME, downloading and installing it ..."
113 | Write-Verbose "Downloading from: $distributionUrl"
114 | Write-Verbose "Downloading to: $TMP_DOWNLOAD_DIR/$distributionUrlName"
115 | 
116 | $webclient = New-Object System.Net.WebClient
117 | if ($env:MVNW_USERNAME -and $env:MVNW_PASSWORD) {
118 |   $webclient.Credentials = New-Object System.Net.NetworkCredential($env:MVNW_USERNAME, $env:MVNW_PASSWORD)
119 | }
120 | [Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
121 | $webclient.DownloadFile($distributionUrl, "$TMP_DOWNLOAD_DIR/$distributionUrlName") | Out-Null
122 | 
123 | # If specified, validate the SHA-256 sum of the Maven distribution zip file
124 | $distributionSha256Sum = (Get-Content -Raw "$scriptDir/.mvn/wrapper/maven-wrapper.properties" | ConvertFrom-StringData).distributionSha256Sum
125 | if ($distributionSha256Sum) {
126 |   if ($USE_MVND) {
127 |     Write-Error "Checksum validation is not supported for maven-mvnd. `nPlease disable validation by removing 'distributionSha256Sum' from your maven-wrapper.properties."
128 |   }
129 |   Import-Module $PSHOME\Modules\Microsoft.PowerShell.Utility -Function Get-FileHash
130 |   if ((Get-FileHash "$TMP_DOWNLOAD_DIR/$distributionUrlName" -Algorithm SHA256).Hash.ToLower() -ne $distributionSha256Sum) {
131 |     Write-Error "Error: Failed to validate Maven distribution SHA-256, your Maven distribution might be compromised. If you updated your Maven version, you need to update the specified distributionSha256Sum property."
132 |   }
133 | }
134 | 
135 | # unzip and move
136 | Expand-Archive "$TMP_DOWNLOAD_DIR/$distributionUrlName" -DestinationPath "$TMP_DOWNLOAD_DIR" | Out-Null
137 | Rename-Item -Path "$TMP_DOWNLOAD_DIR/$distributionUrlNameMain" -NewName $MAVEN_HOME_NAME | Out-Null
138 | try {
139 |   Move-Item -Path "$TMP_DOWNLOAD_DIR/$MAVEN_HOME_NAME" -Destination $MAVEN_HOME_PARENT | Out-Null
140 | } catch {
141 |   if (! (Test-Path -Path "$MAVEN_HOME" -PathType Container)) {
142 |     Write-Error "fail to move MAVEN_HOME"
143 |   }
144 | } finally {
145 |   try { Remove-Item $TMP_DOWNLOAD_DIR -Recurse -Force | Out-Null }
146 |   catch { Write-Warning "Cannot remove $TMP_DOWNLOAD_DIR" }
147 | }
148 | 
149 | Write-Output "MVN_CMD=$MAVEN_HOME/bin/$MVN_CMD"
150 | 


--------------------------------------------------------------------------------
/README.md:
--------------------------------------------------------------------------------
  1 | # Hello Flash: Spring Boot + Gemini API with OpenAI Compatibility
  2 | 
  3 | ![Spring Boot + Gemini](https://img.shields.io/badge/Spring%20Boot-3.4.3-brightgreen)
  4 | ![Spring AI](https://img.shields.io/badge/Spring%20AI-1.0.0--M6-blue)
  5 | ![Java](https://img.shields.io/badge/Java-23-orange)
  6 | 
  7 | ## Introduction
  8 | 
  9 | **Hello Flash** demonstrates how to leverage Google's Gemini models through Spring Boot using OpenAI-compatible endpoints. This project showcases the simplicity of connecting to Google's advanced AI models while maintaining compatibility with familiar OpenAI client libraries and patterns.
 10 | 
 11 | While Google plans to release an official Java SDK for Gemini in the future, this OpenAI compatibility layer provides an excellent workaround for Java developers. With just a few configuration changes, you can redirect your existing OpenAI-based applications to use Gemini's powerful language models using only an API key. This approach allows for seamless integration while taking advantage of Gemini's capabilities.
 12 | 
 13 | ## Project Overview
 14 | 
 15 | This Spring Boot application provides:
 16 | 
 17 | 1. A command-line example that queries Gemini for an interesting fact about Google
 18 | 2. A REST endpoint to list available Gemini models
 19 | 3. Configuration settings to use Spring AI with Gemini's OpenAI-compatible API
 20 | 
 21 | ## Project Requirements
 22 | 
 23 | - Java 23
 24 | - Maven 3.8+
 25 | - Gemini API key
 26 | - Internet connection to access Gemini API endpoints
 27 | 
 28 | ## Dependencies
 29 | 
 30 | The project relies on the following key dependencies:
 31 | 
 32 | - **Spring Boot 3.4.3**: Foundation framework
 33 | - **Spring AI OpenAI Starter 1.0.0-M6**: Spring's AI integration with OpenAI-compatible APIs
 34 | - **Spring Web**: For creating the REST controller
 35 | 
 36 | The complete dependency list is managed through Maven in the `pom.xml` file.
 37 | 
 38 | ## Getting Started
 39 | 
 40 | ### API Key Setup
 41 | 
 42 | Before running the application, you need to obtain a Gemini API key:
 43 | 
 44 | 1. Visit the [Google AI Studio](https://ai.google.dev/) and create an account if needed
 45 | 2. Navigate to the API keys section
 46 | 3. Generate a new API key
 47 | 4. Copy your API key for the next step
 48 | 
 49 | ### Configuration
 50 | 
 51 | Update the `application.properties` file with your Gemini API key:
 52 | 
 53 | ```properties
 54 | spring.ai.openai.api-key=YOUR_GEMINI_API_KEY
 55 | ```
 56 | 
 57 | The other configurations in `application.properties` are already set up to point to Gemini's API endpoints:
 58 | 
 59 | ```properties
 60 | spring.ai.openai.chat.base-url=https://generativelanguage.googleapis.com
 61 | spring.ai.openai.chat.completions-path=/v1beta/openai/chat/completions
 62 | spring.ai.openai.chat.options.model=gemini-2.0-flash
 63 | ```
 64 | 
 65 | ## Running the Application
 66 | 
 67 | ### Using Maven
 68 | 
 69 | To run the application using Maven:
 70 | 
 71 | ```bash
 72 | mvn spring-boot:run
 73 | ```
 74 | 
 75 | ### Using Java
 76 | 
 77 | Alternatively, you can build and run the application:
 78 | 
 79 | ```bash
 80 | mvn clean package
 81 | java -jar target/hello-flash-0.0.1-SNAPSHOT.jar
 82 | ```
 83 | 
 84 | Upon startup, the application will:
 85 | 
 86 | 1. Execute the `CommandLineRunner` which queries Gemini for an interesting fact about Google
 87 | 2. Expose a REST endpoint at `/models` to list available Gemini models
 88 | 
 89 | ## Code Examples
 90 | 
 91 | ### Command Line Interaction
 92 | 
 93 | The main application demonstrates how to create a simple prompt to Gemini:
 94 | 
 95 | ```java
 96 | @Bean
 97 | CommandLineRunner commandLineRunner(ChatClient.Builder builder) {
 98 |     return args -> {
 99 |         var client = builder.build();
100 |         var response = client.prompt("Tell me an interesting fact about Google")
101 |                 .call()
102 |                 .content();
103 | 
104 |         System.out.println(response);
105 |     };
106 | }
107 | ```
108 | 
109 | ### REST Controller for Model Discovery
110 | 
111 | The application includes a controller to fetch available Gemini models. Unlike the command-line example, this doesn't use Spring AI but demonstrates a direct REST API approach using Spring's RestClient. This is particularly useful when you need to discover what models are available without prior knowledge:
112 | 
113 | ```java
114 | @RestController
115 | public class GeminiModelController {
116 | 
117 |     @Value("${spring.ai.openai.api-key}")
118 |     private String GEMINI_API_KEY;
119 |     private final RestClient restClient;
120 | 
121 |     public GeminiModelController(RestClient.Builder builder) {
122 |         this.restClient = builder
123 |                 .baseUrl("https://generativelanguage.googleapis.com")
124 |                 .build();
125 |     }
126 | 
127 |     @GetMapping("/models")
128 |     public List<GeminiModel> models() {
129 |         ResponseEntity<ModelListResponse> response = restClient.get()
130 |                 .uri("/v1beta/openai/models")
131 |                 .header("Authorization","Bearer " + GEMINI_API_KEY)
132 |                 .retrieve()
133 |                 .toEntity(ModelListResponse.class);
134 |         return response.getBody().data();
135 |     }
136 | }
137 | ```
138 | 
139 | ### Direct API Call Example
140 | 
141 | If you prefer to call the API directly without using Spring AI, you can use curl:
142 | 
143 | ```bash
144 | curl "https://generativelanguage.googleapis.com/v1beta/openai/chat/completions" \
145 | -H "Content-Type: application/json" \
146 | -H "Authorization: Bearer YOUR_GEMINI_API_KEY" \
147 | -d '{
148 |     "model": "gemini-2.0-flash",
149 |     "messages": [
150 |         {"role": "user", "content": "Explain to me how AI works"}
151 |     ]
152 | }'
153 | ```
154 | 
155 | ## How It Works
156 | 
157 | This project leverages Spring AI's OpenAI integration but reconfigures it to work with Gemini's API:
158 | 
159 | 1. The base URL is changed to Gemini's endpoint (`generativelanguage.googleapis.com`)
160 | 2. The completions path is set to Gemini's OpenAI-compatible endpoint
161 | 3. The API key is set to your Gemini API key
162 | 4. The model is specified as `gemini-2.0-flash` (Gemini's fastest model)
163 | 
164 | The magic happens in the `application.properties` file, where these configurations redirect all Spring AI OpenAI client calls to Gemini's API.
165 | 
166 | ## Advanced Usage
167 | 
168 | ### Working with Different Gemini Models
169 | 
170 | Gemini offers several models with different capabilities. To use a different model:
171 | 
172 | ```properties
173 | spring.ai.openai.chat.options.model=gemini-2.0-pro
174 | ```
175 | 
176 | Available models include:
177 | - `gemini-2.0-flash` (Fast responses)
178 | - `gemini-2.0-pro` (Higher quality)
179 | - `gemini-1.5-pro` (Previous generation)
180 | 
181 | Check the `/models` endpoint to see the complete list of available models.
182 | 
183 | ### Custom Model Parameters
184 | 
185 | For advanced control over model behavior, you can modify your chat client:
186 | 
187 | ```java
188 | var options = ChatOptions.builder()
189 |     .withTemperature(0.7f)  // Control randomness (0.0 to 1.0)
190 |     .withMaxTokens(1024)    // Limit response length
191 |     .build();
192 | 
193 | var client = builder
194 |     .withOptions(options)
195 |     .build();
196 | ```
197 | 
198 | ## Troubleshooting
199 | 
200 | ### Common Issues
201 | 
202 | 1. **Authentication Error**: Make sure your Gemini API key is correct and properly set in `application.properties`
203 | 
204 | 2. **Model Unavailable**: Verify that the model specified is available in your region. Use the `/models` endpoint to check available models.
205 | 
206 | 3. **Rate Limiting**: Gemini API has rate limits. Check the response headers for rate limit information.
207 | 
208 | ## Conclusion
209 | 
210 | The **Hello Flash** project demonstrates the flexibility of Spring AI and the OpenAI compatibility of Google's Gemini models. By redirecting API calls to Gemini's endpoints, you can easily switch between AI providers while maintaining a consistent development experience.
211 | 
212 | This approach allows you to:
213 | - Leverage existing Spring AI and OpenAI knowledge
214 | - Experiment with different AI providers
215 | - Build applications that can work with multiple AI backends
216 | 
217 | Try extending this project with more complex prompts, different Gemini models, or additional Spring AI features.
218 | 
219 | ## Resources
220 | 
221 | - [Spring AI Documentation](https://docs.spring.io/spring-ai/reference/index.html)
222 | - [Google AI Studio](https://ai.google.dev/)
223 | - [Gemini API Documentation](https://ai.google.dev/docs/gemini_api_overview)


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/mvnw:
--------------------------------------------------------------------------------
  1 | #!/bin/sh
  2 | # ----------------------------------------------------------------------------
  3 | # Licensed to the Apache Software Foundation (ASF) under one
  4 | # or more contributor license agreements.  See the NOTICE file
  5 | # distributed with this work for additional information
  6 | # regarding copyright ownership.  The ASF licenses this file
  7 | # to you under the Apache License, Version 2.0 (the
  8 | # "License"); you may not use this file except in compliance
  9 | # with the License.  You may obtain a copy of the License at
 10 | #
 11 | #    http://www.apache.org/licenses/LICENSE-2.0
 12 | #
 13 | # Unless required by applicable law or agreed to in writing,
 14 | # software distributed under the License is distributed on an
 15 | # "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 16 | # KIND, either express or implied.  See the License for the
 17 | # specific language governing permissions and limitations
 18 | # under the License.
 19 | # ----------------------------------------------------------------------------
 20 | 
 21 | # ----------------------------------------------------------------------------
 22 | # Apache Maven Wrapper startup batch script, version 3.3.2
 23 | #
 24 | # Optional ENV vars
 25 | # -----------------
 26 | #   JAVA_HOME - location of a JDK home dir, required when download maven via java source
 27 | #   MVNW_REPOURL - repo url base for downloading maven distribution
 28 | #   MVNW_USERNAME/MVNW_PASSWORD - user and password for downloading maven
 29 | #   MVNW_VERBOSE - true: enable verbose log; debug: trace the mvnw script; others: silence the output
 30 | # ----------------------------------------------------------------------------
 31 | 
 32 | set -euf
 33 | [ "${MVNW_VERBOSE-}" != debug ] || set -x
 34 | 
 35 | # OS specific support.
 36 | native_path() { printf %s\\n "$1"; }
 37 | case "$(uname)" in
 38 | CYGWIN* | MINGW*)
 39 |   [ -z "${JAVA_HOME-}" ] || JAVA_HOME="$(cygpath --unix "$JAVA_HOME")"
 40 |   native_path() { cygpath --path --windows "$1"; }
 41 |   ;;
 42 | esac
 43 | 
 44 | # set JAVACMD and JAVACCMD
 45 | set_java_home() {
 46 |   # For Cygwin and MinGW, ensure paths are in Unix format before anything is touched
 47 |   if [ -n "${JAVA_HOME-}" ]; then
 48 |     if [ -x "$JAVA_HOME/jre/sh/java" ]; then
 49 |       # IBM's JDK on AIX uses strange locations for the executables
 50 |       JAVACMD="$JAVA_HOME/jre/sh/java"
 51 |       JAVACCMD="$JAVA_HOME/jre/sh/javac"
 52 |     else
 53 |       JAVACMD="$JAVA_HOME/bin/java"
 54 |       JAVACCMD="$JAVA_HOME/bin/javac"
 55 | 
 56 |       if [ ! -x "$JAVACMD" ] || [ ! -x "$JAVACCMD" ]; then
 57 |         echo "The JAVA_HOME environment variable is not defined correctly, so mvnw cannot run." >&2
 58 |         echo "JAVA_HOME is set to \"$JAVA_HOME\", but \"\$JAVA_HOME/bin/java\" or \"\$JAVA_HOME/bin/javac\" does not exist." >&2
 59 |         return 1
 60 |       fi
 61 |     fi
 62 |   else
 63 |     JAVACMD="$(
 64 |       'set' +e
 65 |       'unset' -f command 2>/dev/null
 66 |       'command' -v java
 67 |     )" || :
 68 |     JAVACCMD="$(
 69 |       'set' +e
 70 |       'unset' -f command 2>/dev/null
 71 |       'command' -v javac
 72 |     )" || :
 73 | 
 74 |     if [ ! -x "${JAVACMD-}" ] || [ ! -x "${JAVACCMD-}" ]; then
 75 |       echo "The java/javac command does not exist in PATH nor is JAVA_HOME set, so mvnw cannot run." >&2
 76 |       return 1
 77 |     fi
 78 |   fi
 79 | }
 80 | 
 81 | # hash string like Java String::hashCode
 82 | hash_string() {
 83 |   str="${1:-}" h=0
 84 |   while [ -n "$str" ]; do
 85 |     char="${str%"${str#?}"}"
 86 |     h=$(((h * 31 + $(LC_CTYPE=C printf %d "'$char")) % 4294967296))
 87 |     str="${str#?}"
 88 |   done
 89 |   printf %x\\n $h
 90 | }
 91 | 
 92 | verbose() { :; }
 93 | [ "${MVNW_VERBOSE-}" != true ] || verbose() { printf %s\\n "${1-}"; }
 94 | 
 95 | die() {
 96 |   printf %s\\n "$1" >&2
 97 |   exit 1
 98 | }
 99 | 
100 | trim() {
101 |   # MWRAPPER-139:
102 |   #   Trims trailing and leading whitespace, carriage returns, tabs, and linefeeds.
103 |   #   Needed for removing poorly interpreted newline sequences when running in more
104 |   #   exotic environments such as mingw bash on Windows.
105 |   printf "%s" "${1}" | tr -d '[:space:]'
106 | }
107 | 
108 | # parse distributionUrl and optional distributionSha256Sum, requires .mvn/wrapper/maven-wrapper.properties
109 | while IFS="=" read -r key value; do
110 |   case "${key-}" in
111 |   distributionUrl) distributionUrl=$(trim "${value-}") ;;
112 |   distributionSha256Sum) distributionSha256Sum=$(trim "${value-}") ;;
113 |   esac
114 | done <"${0%/*}/.mvn/wrapper/maven-wrapper.properties"
115 | [ -n "${distributionUrl-}" ] || die "cannot read distributionUrl property in ${0%/*}/.mvn/wrapper/maven-wrapper.properties"
116 | 
117 | case "${distributionUrl##*/}" in
118 | maven-mvnd-*bin.*)
119 |   MVN_CMD=mvnd.sh _MVNW_REPO_PATTERN=/maven/mvnd/
120 |   case "${PROCESSOR_ARCHITECTURE-}${PROCESSOR_ARCHITEW6432-}:$(uname -a)" in
121 |   *AMD64:CYGWIN* | *AMD64:MINGW*) distributionPlatform=windows-amd64 ;;
122 |   :Darwin*x86_64) distributionPlatform=darwin-amd64 ;;
123 |   :Darwin*arm64) distributionPlatform=darwin-aarch64 ;;
124 |   :Linux*x86_64*) distributionPlatform=linux-amd64 ;;
125 |   *)
126 |     echo "Cannot detect native platform for mvnd on $(uname)-$(uname -m), use pure java version" >&2
127 |     distributionPlatform=linux-amd64
128 |     ;;
129 |   esac
130 |   distributionUrl="${distributionUrl%-bin.*}-$distributionPlatform.zip"
131 |   ;;
132 | maven-mvnd-*) MVN_CMD=mvnd.sh _MVNW_REPO_PATTERN=/maven/mvnd/ ;;
133 | *) MVN_CMD="mvn${0##*/mvnw}" _MVNW_REPO_PATTERN=/org/apache/maven/ ;;
134 | esac
135 | 
136 | # apply MVNW_REPOURL and calculate MAVEN_HOME
137 | # maven home pattern: ~/.m2/wrapper/dists/{apache-maven-<version>,maven-mvnd-<version>-<platform>}/<hash>
138 | [ -z "${MVNW_REPOURL-}" ] || distributionUrl="$MVNW_REPOURL$_MVNW_REPO_PATTERN${distributionUrl#*"$_MVNW_REPO_PATTERN"}"
139 | distributionUrlName="${distributionUrl##*/}"
140 | distributionUrlNameMain="${distributionUrlName%.*}"
141 | distributionUrlNameMain="${distributionUrlNameMain%-bin}"
142 | MAVEN_USER_HOME="${MAVEN_USER_HOME:-${HOME}/.m2}"
143 | MAVEN_HOME="${MAVEN_USER_HOME}/wrapper/dists/${distributionUrlNameMain-}/$(hash_string "$distributionUrl")"
144 | 
145 | exec_maven() {
146 |   unset MVNW_VERBOSE MVNW_USERNAME MVNW_PASSWORD MVNW_REPOURL || :
147 |   exec "$MAVEN_HOME/bin/$MVN_CMD" "$@" || die "cannot exec $MAVEN_HOME/bin/$MVN_CMD"
148 | }
149 | 
150 | if [ -d "$MAVEN_HOME" ]; then
151 |   verbose "found existing MAVEN_HOME at $MAVEN_HOME"
152 |   exec_maven "$@"
153 | fi
154 | 
155 | case "${distributionUrl-}" in
156 | *?-bin.zip | *?maven-mvnd-?*-?*.zip) ;;
157 | *) die "distributionUrl is not valid, must match *-bin.zip or maven-mvnd-*.zip, but found '${distributionUrl-}'" ;;
158 | esac
159 | 
160 | # prepare tmp dir
161 | if TMP_DOWNLOAD_DIR="$(mktemp -d)" && [ -d "$TMP_DOWNLOAD_DIR" ]; then
162 |   clean() { rm -rf -- "$TMP_DOWNLOAD_DIR"; }
163 |   trap clean HUP INT TERM EXIT
164 | else
165 |   die "cannot create temp dir"
166 | fi
167 | 
168 | mkdir -p -- "${MAVEN_HOME%/*}"
169 | 
170 | # Download and Install Apache Maven
171 | verbose "Couldn't find MAVEN_HOME, downloading and installing it ..."
172 | verbose "Downloading from: $distributionUrl"
173 | verbose "Downloading to: $TMP_DOWNLOAD_DIR/$distributionUrlName"
174 | 
175 | # select .zip or .tar.gz
176 | if ! command -v unzip >/dev/null; then
177 |   distributionUrl="${distributionUrl%.zip}.tar.gz"
178 |   distributionUrlName="${distributionUrl##*/}"
179 | fi
180 | 
181 | # verbose opt
182 | __MVNW_QUIET_WGET=--quiet __MVNW_QUIET_CURL=--silent __MVNW_QUIET_UNZIP=-q __MVNW_QUIET_TAR=''
183 | [ "${MVNW_VERBOSE-}" != true ] || __MVNW_QUIET_WGET='' __MVNW_QUIET_CURL='' __MVNW_QUIET_UNZIP='' __MVNW_QUIET_TAR=v
184 | 
185 | # normalize http auth
186 | case "${MVNW_PASSWORD:+has-password}" in
187 | '') MVNW_USERNAME='' MVNW_PASSWORD='' ;;
188 | has-password) [ -n "${MVNW_USERNAME-}" ] || MVNW_USERNAME='' MVNW_PASSWORD='' ;;
189 | esac
190 | 
191 | if [ -z "${MVNW_USERNAME-}" ] && command -v wget >/dev/null; then
192 |   verbose "Found wget ... using wget"
193 |   wget ${__MVNW_QUIET_WGET:+"$__MVNW_QUIET_WGET"} "$distributionUrl" -O "$TMP_DOWNLOAD_DIR/$distributionUrlName" || die "wget: Failed to fetch $distributionUrl"
194 | elif [ -z "${MVNW_USERNAME-}" ] && command -v curl >/dev/null; then
195 |   verbose "Found curl ... using curl"
196 |   curl ${__MVNW_QUIET_CURL:+"$__MVNW_QUIET_CURL"} -f -L -o "$TMP_DOWNLOAD_DIR/$distributionUrlName" "$distributionUrl" || die "curl: Failed to fetch $distributionUrl"
197 | elif set_java_home; then
198 |   verbose "Falling back to use Java to download"
199 |   javaSource="$TMP_DOWNLOAD_DIR/Downloader.java"
200 |   targetZip="$TMP_DOWNLOAD_DIR/$distributionUrlName"
201 |   cat >"$javaSource" <<-END
202 | 	public class Downloader extends java.net.Authenticator
203 | 	{
204 | 	  protected java.net.PasswordAuthentication getPasswordAuthentication()
205 | 	  {
206 | 	    return new java.net.PasswordAuthentication( System.getenv( "MVNW_USERNAME" ), System.getenv( "MVNW_PASSWORD" ).toCharArray() );
207 | 	  }
208 | 	  public static void main( String[] args ) throws Exception
209 | 	  {
210 | 	    setDefault( new Downloader() );
211 | 	    java.nio.file.Files.copy( java.net.URI.create( args[0] ).toURL().openStream(), java.nio.file.Paths.get( args[1] ).toAbsolutePath().normalize() );
212 | 	  }
213 | 	}
214 | 	END
215 |   # For Cygwin/MinGW, switch paths to Windows format before running javac and java
216 |   verbose " - Compiling Downloader.java ..."
217 |   "$(native_path "$JAVACCMD")" "$(native_path "$javaSource")" || die "Failed to compile Downloader.java"
218 |   verbose " - Running Downloader.java ..."
219 |   "$(native_path "$JAVACMD")" -cp "$(native_path "$TMP_DOWNLOAD_DIR")" Downloader "$distributionUrl" "$(native_path "$targetZip")"
220 | fi
221 | 
222 | # If specified, validate the SHA-256 sum of the Maven distribution zip file
223 | if [ -n "${distributionSha256Sum-}" ]; then
224 |   distributionSha256Result=false
225 |   if [ "$MVN_CMD" = mvnd.sh ]; then
226 |     echo "Checksum validation is not supported for maven-mvnd." >&2
227 |     echo "Please disable validation by removing 'distributionSha256Sum' from your maven-wrapper.properties." >&2
228 |     exit 1
229 |   elif command -v sha256sum >/dev/null; then
230 |     if echo "$distributionSha256Sum  $TMP_DOWNLOAD_DIR/$distributionUrlName" | sha256sum -c >/dev/null 2>&1; then
231 |       distributionSha256Result=true
232 |     fi
233 |   elif command -v shasum >/dev/null; then
234 |     if echo "$distributionSha256Sum  $TMP_DOWNLOAD_DIR/$distributionUrlName" | shasum -a 256 -c >/dev/null 2>&1; then
235 |       distributionSha256Result=true
236 |     fi
237 |   else
238 |     echo "Checksum validation was requested but neither 'sha256sum' or 'shasum' are available." >&2
239 |     echo "Please install either command, or disable validation by removing 'distributionSha256Sum' from your maven-wrapper.properties." >&2
240 |     exit 1
241 |   fi
242 |   if [ $distributionSha256Result = false ]; then
243 |     echo "Error: Failed to validate Maven distribution SHA-256, your Maven distribution might be compromised." >&2
244 |     echo "If you updated your Maven version, you need to update the specified distributionSha256Sum property." >&2
245 |     exit 1
246 |   fi
247 | fi
248 | 
249 | # unzip and move
250 | if command -v unzip >/dev/null; then
251 |   unzip ${__MVNW_QUIET_UNZIP:+"$__MVNW_QUIET_UNZIP"} "$TMP_DOWNLOAD_DIR/$distributionUrlName" -d "$TMP_DOWNLOAD_DIR" || die "failed to unzip"
252 | else
253 |   tar xzf${__MVNW_QUIET_TAR:+"$__MVNW_QUIET_TAR"} "$TMP_DOWNLOAD_DIR/$distributionUrlName" -C "$TMP_DOWNLOAD_DIR" || die "failed to untar"
254 | fi
255 | printf %s\\n "$distributionUrl" >"$TMP_DOWNLOAD_DIR/$distributionUrlNameMain/mvnw.url"
256 | mv -- "$TMP_DOWNLOAD_DIR/$distributionUrlNameMain" "$MAVEN_HOME" || [ -d "$MAVEN_HOME" ] || die "fail to move MAVEN_HOME"
257 | 
258 | clean || :
259 | exec_maven "$@"
260 | 


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