一、文字转语音API介绍

近年来，随着人工智能技术的飞速发展，文字转语音技术也日渐成熟。目前市面上已经出现了许多文字转语音的API，其中最为知名的当属百度AI开放平台、阿里云智能语音等。这些API功能强大、使用方便，且还支持多种语言转换，可以满足各种场景的需求。

二、Java实现API调用

Java作为一种广泛应用于企业开发的编程语言，自然也支持文字转语音API的调用。以百度AI开放平台为例，需要先在官网进行注册、申请API密钥等操作，然后通过Java代码调用接口进行文字转语音。下面是示例代码：

public class BaiduAiService{
    public static void main(String[] args) {
        String API_KEY = "your_api_key";
        String SECRET_KEY = "your_secret_key";
        // 初始化一个AipSpeech
        AipSpeech client = new AipSpeech(API_KEY, SECRET_KEY);
        // 调用接口转换文字为语音
        TtsResponse res = client.synthesis("百度AI开放平台，让AI变得简单", "zh", 1, null);
        // 将语音转换成文件保存
        FileOutputStream fos = new FileOutputStream(new File("out.mp3"));
        byte[] bytes = res.getData();
        fos.write(bytes, 0, bytes.length);
        fos.flush();
        fos.close();
    }
}

三、Java实现本地语音合成

除了调用文字转语音API外，Java还可以使用本地语音合成技术，也就是使用Java自带的javax.speech包进行文字合成。该包是Java Speech API的一部分，旨在提供一种用于语音合成及识别的Java标准。下面是示例代码：

import javax.sound.sampled.AudioFileFormat;
import javax.sound.sampled.AudioInputStream;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.Clip;
import javax.sound.sampled.DataLine;
import javax.sound.sampled.Mixer;
import javax.sound.sampled.Port;
import javax.sound.sampled.SourceDataLine;
import javax.sound.sampled.TargetDataLine;
import javax.sound.sampled.AudioFormat.Encoding;
import javax.speech.AudioException;
import javax.speech.Central;
import javax.speech.EngineList;
import javax.speech.EngineModeDesc;
import javax.speech.synthesis.SpeechEvent;
import javax.speech.synthesis.SpeechEventAdapter;
import javax.speech.synthesis.Synthesizer;
import javax.speech.synthesis.SynthesizerModeDesc;
public class TTS {
    private Synthesizer synthesizer;
    public void setText(String text) {
        try {
            // 获取SynthesizerModeDesc描述类
            SynthesizerModeDesc desc = new SynthesizerModeDesc(null, "general", Locale.US, null, null);
            // 根据描述类创建Synthesizer对象
            synthesizer = Central.createSynthesizer(desc);
            // 打开Synthesizer
            synthesizer.allocate();
            synthesizer.resume();
            // 添加监听器
            synthesizer.addEngineListener(new CustomSynthesizerListener());
            // 将文本输入Synthesizer，并设置语音合成的音量、语速、音调等参数
            synthesizer.speak(text, null);
            synthesizer.waitEngineState(Synthesizer.QUEUE_EMPTY);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (synthesizer != null)
                synthesizer.deallocate();
        }
    }
    /**
     * 监听器
     */
    private class CustomSynthesizerListener extends SpeechEventAdapter {
        @Override
        public void processUnknown(SpeechEvent e) {
            System.out.println("唤醒：" + e.getSource() + " " + e.getId() + " " + e.getText());
        }
    }
    public static void main(String[] args) {
        TTS tts = new TTS();
        tts.setText("Java语音合成工具，方便易用，支持多种参数设置");
    }
}

四、Java实现语音转文字

除了文字转语音，Java也支持语音转文字功能。相比文字转语音，语音转文字需要更多的算法处理。目前市面上也有很多成熟的语音转文字API，如讯飞开放平台、腾讯AI开放平台等。下面是使用讯飞开放平台API进行语音转文字的示例代码：

public class XunfeiDemo {
    private static final String URL = "http://api.xfyun.cn/v1/service/v1/iat";
    private static final String APP_ID = "your_app_id";
    private static final String API_KEY = "your_api_key";
    private static final String API_SECRET = "your_api_secret";
    // 音频编码
    private static final String AUE = "raw";
    // 结果格式
    private static final String RESULT_FORMAT = "json";
    public static void main(String[] args) throws Exception {
        File file = new File("test.pcm");
        FileInputStream fis = new FileInputStream(file);
        byte[] bytes = new byte[fis.available()];
        fis.read(bytes);
        fis.close();
        String audioBase64 = new BASE64Encoder().encode(bytes);
        String curTime = System.currentTimeMillis() / 1000L + "";
        String param = "{\"auf\":\"audio/L16;rate=16000\",\"aue\":\"" + AUE + "\",\"voice_name\":\"xiaoyan\",\"engine_type\":\"sms16k\",\"result_format\":\"" + RESULT_FORMAT + "\",\"grammar_list\":\"\",\"extend_params\":\"language=cn|accent=mun\",\"sub\":\"iat\",\"index\":0,\"language\":\"zh_cn\"}";
        String paramBase64 = new BASE64Encoder().encode(param.getBytes("UTF-8"));
        // 计算请求签名
        String checkSum = DigestUtils.md5Hex(API_KEY + curTime + paramBase64).toLowerCase();
        CloseableHttpClient httpClient = HttpClients.createDefault();
        HttpPost httpPost = new HttpPost(URL);
        httpPost.setHeader("Content-Type", "application/x-www-form-urlencoded; charset=utf-8");
        httpPost.setHeader("X-CurTime", curTime);
        httpPost.setHeader("X-Param", paramBase64);
        httpPost.setHeader("X-Appid", APP_ID);
        httpPost.setHeader("X-CheckSum", checkSum);
        httpPost.setHeader("X-UserAgent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:84.0) Gecko/20100101 Firefox/84.0");
        StringEntity reqEntity = new StringEntity("audio=" + URLEncoder.encode(audioBase64, "UTF-8"), "UTF-8");
        httpPost.setEntity(reqEntity);
        CloseableHttpResponse httpResponse = httpClient.execute(httpPost);
        String result = EntityUtils.toString(httpResponse.getEntity(), "UTF-8");
        JSONObject jsonObject = JSONObject.parseObject(result);
        JSONArray jsonArray = jsonObject.getJSONObject("data").getJSONArray("result");
        StringBuilder stringBuilder = new StringBuilder();
        for (Object obj : jsonArray) {
            stringBuilder.append(obj.toString());
        }
        System.out.println(stringBuilder.toString());
    }
}