代码一：

public String generateQRCode(String appId, String appSecret, String pagePath) throws IOException {
    String accessToken = getAccessToken(appId, appSecret);
    String apiUrl = "https://api.weixin.qq.com/wxa/getwxacodeunlimit?access_token=" + accessToken;

    URL url = new URL(apiUrl);
    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
    connection.setRequestMethod("POST");
    connection.setDoOutput(true);
    connection.setRequestProperty("Content-Type", "application/json");

    JSONObject requestBody = new JSONObject();
    requestBody.put("scene", pagePath); // 指定体验版的路径
    requestBody.put("width", 280);

    OutputStream outputStream = connection.getOutputStream();
    outputStream.write(requestBody.toString().getBytes());
    outputStream.flush();
    outputStream.close();

    int responseCode = connection.getResponseCode();
    if (responseCode == HttpURLConnection.HTTP_OK) {
        InputStream inputStream = connection.getInputStream();
        // 处理返回的小程序码图片数据
        // ...
        inputStream.close();
    } else {
        throw new IOException("HTTP response code: " + responseCode);
    }
    return null;
}

private String getAccessToken(String appId, String appSecret) throws IOException {
    String apiUrl = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=" + appId + "&secret=" + appSecret;

    URL url = new URL(apiUrl);
    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
    connection.setRequestMethod("GET");

    int responseCode = connection.getResponseCode();
    if (responseCode == HttpURLConnection.HTTP_OK) {
        InputStream inputStream = connection.getInputStream();
        // 处理返回的 access token 数据
        // ...
        inputStream.close();
    } else {
        throw new IOException("HTTP response code: " + responseCode);
    }
    return null;
}

代码二：

 controller部分：

    //生成小程序码方式
    @PostMapping("/generate/applet")
    public ResponseEntity<byte[]> generateQRCode(@RequestBody CodeData codeData, HttpServletResponse response) throws IOException {
//        System.out.println(codeData);
        String accessToken = weChatApiService.getAccessTokenTwo(codeData.getOpenId(), codeData.getAppSecret());
        String page = codeData.getPage();
        byte[] imageBytes = qrCodeImg.generateMiniProgramQRCode(accessToken,codeData.getScene(),page);


        // 设置响应头部
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.IMAGE_JPEG);
        headers.setContentLength(imageBytes.length);

        // 返回图片数据
        return new ResponseEntity<>(imageBytes, headers, HttpStatus.OK);

    }

获取access_token部分：

import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;
import org.springframework.web.reactive.function.client.WebClient;

@Service
public class WeChatApiService {
//    @Value("${wechat.appId}")
//    private String appId;
//
//    @Value("${wechat.appSecret}")
//    private String appSecret;

    public String getAccessTokenOne(String appId, String appSecret) {
        String url = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=" + appId + "&secret=" + appSecret;

        WebClient client = WebClient.create();
        AccessTokenResponse response = client.get()
                .uri(url)
                .retrieve()
                .bodyToMono(AccessTokenResponse.class)
                .block();

        if (response != null) {
            return response.getAccess_token();
        } else {
            throw new RuntimeException("Failed to get access token.");
        }
    }
    public String getAccessTokenTwo(String appId, String appSecret) {
//        https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=%s&secret=%s
        String url = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=" + appId + "&secret=" + appSecret;

        RestTemplate restTemplate = new RestTemplate();
        AccessTokenResponse response = restTemplate.getForObject(url, AccessTokenResponse.class);

        if (response != null) {
            return response.getAccess_token();
        } else {
            throw new RuntimeException("Failed to get access token.");
        }
    }
}

其他功能类：

import org.springframework.stereotype.Service;
import org.springframework.util.StreamUtils;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

@Service
public class QRCodeImg {

    public byte[] generateMiniProgramQRCode(String accessToken, String scene,String pageEncoded) throws IOException {
        String url = "https://api.weixin.qq.com/wxa/getwxacodeunlimit?access_token=" + accessToken;

//        String url = "https://api.weixin.qq.com/wxa/getwxacode?access_token=" + accessToken;
        // 正式版为 "release"，体验版为 "trial"，开发版为 "develop"。默认是正式版。
        String env_version = "trial";

        // 构建请求参数
//        String postData = "{\"scene\":\"" + scene + "\", \"path\":\"" + pageEncoded + "\", \"width\":430,\"env_version\":\"trial\"}";
        String postData = "{\"scene\":\"" + scene + "\", \"page\":\"" + pageEncoded + "\", \"width\":430,\"env_version\":\""+env_version +"\"}";
//        String postData = "{\"scene\":\"" + scene + "\", \"width\":430,\"env_version\":\"trial\"}";


        // 发送POST请求
        HttpURLConnection connection = (HttpURLConnection) new URL(url).openConnection();
        connection.setRequestMethod("POST");
        connection.setDoOutput(true);
        connection.getOutputStream().write(postData.getBytes("UTF-8"));

        // 读取响应数据
        InputStream inputStream = connection.getInputStream();
        byte[] buffer = StreamUtils.copyToByteArray(inputStream);

        // 解析响应数据，获取小程序码的URL

        return buffer;
    }

    public void saveQRCodeImage(String imageUrl, String filePath) throws IOException {
        System.out.println(imageUrl);
        URL url = new URL(imageUrl);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setRequestMethod("GET");

        // 读取图片数据
        InputStream inputStream = connection.getInputStream();

        // 保存图片到本地文件
        FileOutputStream outputStream = new FileOutputStream(filePath);
        StreamUtils.copy(inputStream, outputStream);

        // 关闭流
        inputStream.close();
        outputStream.close();
    }
}

import lombok.Data;

@Data
public class CodeData {
    private String scene;
    private String openId;
    private String appSecret;
    private String page;
}

三种方式获取小程序码，我用的第三种方式，如下： 

获取小程序二维码 | 微信开放文档微信开发者平台文档https://developers.weixin.qq.com/miniprogram/dev/api-backend/open-api/qr-code/wxacode.createQRCode.html

获取小程序码 | 微信开放文档微信开发者平台文档https://developers.weixin.qq.com/miniprogram/dev/api-backend/open-api/qr-code/wxacode.get.html

获取不限制的小程序码 | 微信开放文档微信开发者平台文档https://developers.weixin.qq.com/miniprogram/dev/api-backend/open-api/qr-code/wxacode.getUnlimited.html微信小程序前端获取参数：

在App.js获取：

App({
  onLaunch(options) {
    console.log(options.query); // 获取小程序码的参数
  }
})