微信公发送推送消息java

要通过 Java 发送微信公众号推送消息，可以使用官方提供的接口和第三方库实现。以下是一个使用官方接口实现的示例代码：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.util.HashMap;
import java.util.Map;

public class WechatPush {
    public static void main(String[] args) {
        // 填写公众号的 appid 和 appsecret
        String appid = "your_appid";
        String appsecret = "your_appsecret";

        // 获取 access_token
        String accessToken = getAccessToken(appid, appsecret);

        // 发送推送消息
        String url = "https://api.weixin.qq.com/cgi-bin/message/custom/send?access_token=" + accessToken;
        String postData = "{\"touser\":\"openid\",\"msgtype\":\"text\",\"text\":{\"content\":\"Hello World\"}}";
        String result = sendPost(url, postData);
        System.out.println(result);
    }

    /**
     * 获取 access_token
     */
    public static String getAccessToken(String appid, String appsecret) {
        String accessToken = null;
        try {
            String url = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=" + appid + "&secret=" + appsecret;
            String result = sendGet(url);
            Map<String, Object> map = parseJson(result);
            if (map.containsKey("access_token")) {
                accessToken = map.get("access_token").toString();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return accessToken;
    }

    /**
     * 发送 GET 请求
     */
    public static String sendGet(String url) throws IOException {
        HttpURLConnection connection = null;
        BufferedReader reader = null;
        StringBuffer result = new StringBuffer();
        try {
            URL requestUrl = new URL(url);
            connection = (HttpURLConnection) requestUrl.openConnection();
            connection.setRequestMethod("GET");
            connection.setConnectTimeout(5000);
            connection.setReadTimeout(5000);
            connection.connect();
            if (connection.getResponseCode() == 200) {
                reader = new BufferedReader(new InputStreamReader(connection.getInputStream(), "UTF-8"));
                String line = null;
                while ((line = reader.readLine()) != null) {
                    result.append(line);
                }
            }
        } finally {
            if (reader != null) {
                reader.close();
            }
            if (connection != null) {
                connection.disconnect();
            }
        }
        return result.toString();
    }

    /**
     * 发送 POST 请求
     */
    public static String sendPost(String url, String data) {
        HttpURLConnection connection = null;
        BufferedReader reader = null;
        StringBuffer result = new StringBuffer();
        try {
            URL requestUrl = new URL(url);
            connection = (HttpURLConnection) requestUrl.openConnection();
            connection.setRequestMethod("POST");
            connection.setConnectTimeout(5000);
            connection.setReadTimeout(5000);
            connection.setDoOutput(true);
            connection.setDoInput(true);
            connection.setRequestProperty("Content-Type", "application/json");
            connection.connect();
            connection.getOutputStream().write(data.getBytes("UTF-8"));
            connection.getOutputStream().flush();
            connection.getOutputStream().close();
            if (connection.getResponseCode() == 200) {
                reader = new BufferedReader(new InputStreamReader(connection.getInputStream(), "UTF-8"));
                String line = null;
                while ((line = reader.readLine()) != null) {
                    result.append(line);
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (reader != null) {
                try {
                    reader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (connection != null) {
                connection.disconnect();
            }
        }
        return result.toString();
    }

    /**
     * 解析 JSON 字符串
     */
    public static Map<String, Object> parseJson(String jsonStr) {
        Map<String, Object> map = new HashMap<>();
        try {
            JSONObject jsonObject = new JSONObject(jsonStr);
            Iterator<String> iterator = jsonObject.keys();
            while (iterator.hasNext()) {
                String key = iterator.next();
                Object value = jsonObject.get(key);
                map.put(key, value);
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }
        return map;
    }
}

其中，`getAccessToken` 方法用于获取 access_token，`sendPost` 方法用于发送 POST 请求，`parseJson` 方法用于解析 JSON 字符串。在发送推送消息时，需要将 openid 和消息内容填写到 postData 中。注意需要将 postData 进行 JSON 序列化。