Text-To-Speech (TTS) API
Spring AI 通过 TextToSpeechModel 和 StreamingTextToSpeechModel 接口为 Text-To-Speech (TTS) 提供统一的 API。这允许您编写可在不同 TTS 提供者之间工作的可移植代码。
Supported Providers
Common Interface
所有 TTS 提供者实现以下共享接口：
TextToSpeechModel
TextToSpeechModel 接口提供将文本转换为语音的方法：
public interface TextToSpeechModel extends Model<TextToSpeechPrompt, TextToSpeechResponse>, StreamingTextToSpeechModel {
/**
* Converts text to speech with default options.
*/
default byte[] call(String text) {
// Default implementation
}
/**
* Converts text to speech with custom options.
*/
TextToSpeechResponse call(TextToSpeechPrompt prompt);
/**
* Returns the default options for this model.
*/
default TextToSpeechOptions getDefaultOptions() {
// Default implementation
}
}
StreamingTextToSpeechModel
StreamingTextToSpeechModel 接口提供实时流式传输音频的方法：
@FunctionalInterface
public interface StreamingTextToSpeechModel extends StreamingModel<TextToSpeechPrompt, TextToSpeechResponse> {
/**
* Streams text-to-speech responses with metadata.
*/
Flux<TextToSpeechResponse> stream(TextToSpeechPrompt prompt);
/**
* Streams audio bytes for the given text.
*/
default Flux<byte[]> stream(String text) {
// Default implementation
}
}
TextToSpeechPrompt
TextToSpeechPrompt 类封装输入文本和选项：
TextToSpeechPrompt prompt = new TextToSpeechPrompt(
"Hello, this is a text-to-speech example.",
options
);
TextToSpeechResponse
TextToSpeechResponse 类包含生成的音频和元数据：
TextToSpeechResponse response = model.call(prompt);
byte[] audioBytes = response.getResult().getOutput();
TextToSpeechResponseMetadata metadata = response.getMetadata();
Writing Provider-Agnostic Code
共享 TTS 接口的主要好处之一是能够编写可在任何 TTS 提供者上工作而无需修改的代码。实际的提供者（OpenAI、ElevenLabs 等）由您的 Spring Boot 配置确定，允许您在不更改应用程序代码的情况下切换提供者。
Basic Service Example
共享接口允许您编写可在任何 TTS 提供者上工作的代码：
@Service
public class NarrationService {
private final TextToSpeechModel textToSpeechModel;
public NarrationService(TextToSpeechModel textToSpeechModel) {
this.textToSpeechModel = textToSpeechModel;
}
public byte[] narrate(String text) {
// Works with any TTS provider
return textToSpeechModel.call(text);
}
public byte[] narrateWithOptions(String text, TextToSpeechOptions options) {
TextToSpeechPrompt prompt = new TextToSpeechPrompt(text, options);
TextToSpeechResponse response = textToSpeechModel.call(prompt);
return response.getResult().getOutput();
}
}
此服务可与 OpenAI、ElevenLabs 或任何其他 TTS 提供者无缝协作，实际实现由您的 Spring Boot 配置确定。
Advanced Example: Multi-Provider Support
您可以构建同时支持多个 TTS 提供者的应用程序：
@Service
public class MultiProviderNarrationService {
private final Map<String, TextToSpeechModel> providers;
public MultiProviderNarrationService(List<TextToSpeechModel> models) {
// Spring will inject all available TextToSpeechModel beans
this.providers = models.stream()
.collect(Collectors.toMap(
model -> model.getClass().getSimpleName(),
model -> model
));
}
public byte[] narrateWithProvider(String text, String providerName) {
TextToSpeechModel model = providers.get(providerName);
if (model == null) {
throw new IllegalArgumentException("Unknown provider: " + providerName);
}
return model.call(text);
}
public Set<String> getAvailableProviders() {
return providers.keySet();
}
}
Streaming Audio Example
共享接口还支持实时音频生成的流式传输：
@Service
public class StreamingNarrationService {
private final TextToSpeechModel textToSpeechModel;
public StreamingNarrationService(TextToSpeechModel textToSpeechModel) {
this.textToSpeechModel = textToSpeechModel;
}
public Flux<byte[]> streamNarration(String text) {
// TextToSpeechModel extends StreamingTextToSpeechModel
return textToSpeechModel.stream(text);
}
public Flux<TextToSpeechResponse> streamWithMetadata(String text, TextToSpeechOptions options) {
TextToSpeechPrompt prompt = new TextToSpeechPrompt(text, options);
return textToSpeechModel.stream(prompt);
}
}
REST Controller Example
使用与提供者无关的 TTS 构建 REST API：
@RestController
@RequestMapping("/api/tts")
public class TextToSpeechController {
private final TextToSpeechModel textToSpeechModel;
public TextToSpeechController(TextToSpeechModel textToSpeechModel) {
this.textToSpeechModel = textToSpeechModel;
}
@PostMapping(value = "/synthesize", produces = "audio/mpeg")
public ResponseEntity<byte[]> synthesize(@RequestBody SynthesisRequest request) {
byte[] audio = textToSpeechModel.call(request.text());
return ResponseEntity.ok()
.contentType(MediaType.parseMediaType("audio/mpeg"))
.header("Content-Disposition", "attachment; filename=\"speech.mp3\"")
.body(audio);
}
@GetMapping(value = "/stream", produces = MediaType.APPLICATION_OCTET_STREAM_VALUE)
public Flux<byte[]> streamSynthesis(@RequestParam String text) {
return textToSpeechModel.stream(text);
}
record SynthesisRequest(String text) {}
}
Configuration-Based Provider Selection
使用 Spring profiles 或属性在提供者之间切换：
# application-openai.yml
spring:
ai:
model:
audio:
speech: openai
openai:
api-key: ${OPENAI_API_KEY}
audio:
speech:
options:
model: gpt-4o-mini-tts
voice: alloy
# application-elevenlabs.yml
spring:
ai:
model:
audio:
speech: elevenlabs
elevenlabs:
api-key: ${ELEVENLABS_API_KEY}
tts:
options:
model-id: eleven_turbo_v2_5
voice-id: your_voice_id
然后激活所需的提供者：
# Use OpenAI
java -jar app.jar --spring.profiles.active=openai
# Use ElevenLabs
java -jar app.jar --spring.profiles.active=elevenlabs
Using Portable Options
为了最大可移植性，仅使用通用 TextToSpeechOptions 接口方法：
@Service
public class PortableNarrationService {
private final TextToSpeechModel textToSpeechModel;
public PortableNarrationService(TextToSpeechModel textToSpeechModel) {
this.textToSpeechModel = textToSpeechModel;
}
public byte[] createPortableNarration(String text) {
// Use provider's default options for maximum portability
TextToSpeechOptions defaultOptions = textToSpeechModel.getDefaultOptions();
TextToSpeechPrompt prompt = new TextToSpeechPrompt(text, defaultOptions);
TextToSpeechResponse response = textToSpeechModel.call(prompt);
return response.getResult().getOutput();
}
}
Working with Provider-Specific Features
当您需要提供者特定功能时，您仍然可以在保持可移植代码库的同时使用它们：
@Service
public class FlexibleNarrationService {
private final TextToSpeechModel textToSpeechModel;
public FlexibleNarrationService(TextToSpeechModel textToSpeechModel) {
this.textToSpeechModel = textToSpeechModel;
}
public byte[] narrate(String text, TextToSpeechOptions baseOptions) {
TextToSpeechOptions options = baseOptions;
// Apply provider-specific optimizations if available
if (textToSpeechModel instanceof OpenAiAudioSpeechModel) {
options = OpenAiAudioSpeechOptions.builder()
.from(baseOptions)
.model("gpt-4o-tts") // OpenAI-specific: use high-quality model
.speed(1.0)
.build();
} else if (textToSpeechModel instanceof ElevenLabsTextToSpeechModel) {
// ElevenLabs-specific options could go here
}
TextToSpeechPrompt prompt = new TextToSpeechPrompt(text, options);
TextToSpeechResponse response = textToSpeechModel.call(prompt);
return response.getResult().getOutput();
}
}
Best Practices for Portable Code
- 依赖接口：始终注入
TextToSpeechModel而不是具体实现 - 使用通用选项：坚持使用
TextToSpeechOptions接口方法以获得最大可移植性 - 优雅处理元数据：不同的提供者返回不同的元数据；通用地处理它
- 使用多个提供者进行测试：确保您的代码至少与两个 TTS 提供者一起工作
- 记录提供者假设：如果您依赖特定的提供者行为，请清楚地记录它
Provider-Specific Features
虽然共享接口提供了可移植性，但每个提供者还通过提供者特定的选项类（例如 OpenAiAudioSpeechOptions、ElevenLabsSpeechOptions）提供特定功能。这些类实现 TextToSpeechOptions 接口，同时添加提供者特定的功能。