小程序一次性订阅消息（消息通知）：java服务端实现

在Java后端实现小程序一次性订阅消息，你需要使用微信官方提供的API，并且确保你有小程序的appId和appSecret。以下是一个简单的Java示例代码，用于发送一次性订阅消息：

import com.google.gson.JsonObject;
import okhttp3.*;
import java.io.IOException;
 
public class WechatMiniProgramSubscribeMessage {
 
    private static final String APP_ID = "你的小程序appId";
    private static final String APP_SECRET = "你的小程序appSecret";
    private static final String ACCESS_TOKEN_URL = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=%s&secret=%s";
    private static final String SUBSCRIBE_MESSAGE_URL = "https://api.weixin.qq.com/cgi-bin/message/subscribe/send?access_token=%s";
 
    public static void sendSubscribeMessage(String openId, String templateId, JsonObject data) throws IOException {
        // 获取access_token
        String accessToken = getAccessToken();
 
        // 发送订阅消息
        sendMessage(accessToken, openId, templateId, data);
    }
 
    private static String getAccessToken() throws IOException {
        OkHttpClient client = new OkHttpClient();
        Request request = new Request.Builder()
                .url(String.format(ACCESS_TOKEN_URL, APP_ID, APP_SECRET))
                .build();
        try (Response response = client.newCall(request).execute()) {
            String responseString = response.body().string();
            JsonObject jsonObject = JsonParser.parseString(responseString).getAsJsonObject();
            return jsonObject.get("access_token").getAsString();
        }
    }
 
    private static void sendMessage(String accessToken, String openId, String templateId, JsonObject data) throws IOException {
        OkHttpClient client = new OkHttpClient();
        JsonObject json = new JsonObject();
        json.addProperty("touser", openId);
        json.addProperty("template_id", templateId);
        json.add("page", null); // 可选
        json.add("data", data);
        MediaType JSON = MediaType.parse("application/json; charset=utf-8");
        RequestBody requestBody = RequestBody.create(JSON, json.toString());
        Request request = new Request.Builder()
                .url(String.format(SUBSCRIBE_MESSAGE_URL, accessToken))
                .post(requestBody)
                .build();
        try (Response response = client.newCall(request).execute()) {
            System.out.println(response.body().string());
        }
    }
 
    public static void main(String[] args) {
        Jso