Java微信小程序开发之获取OpenId和发送（模板）订阅消息推送

1. 获取OpenId
（WechatToken 类 是自己根据实际情况而定封装的类）

public static String sendPostForCode(String code) {

        WechatToken wechatToken = new WechatToken();

        Map<String, String> paramMap = new HashMap<String, String>();
        paramMap.put("appid", wechatToken.getAppId());  //开发者设置中的appId
        paramMap.put("secret", wechatToken.getAppSecret()); //开发者设置中的appSecret
        paramMap.put("js_code", code); //小程序调用wx.login返回的code
        paramMap.put("grant_type", wechatToken.getGrantType());    //默认参数 authorization_code

        PrintWriter out = null;
        BufferedReader in = null;
        String result = "";

        String param = "";
        Iterator<String> it = paramMap.keySet().iterator();

        while (it.hasNext()) {
            String key = it.next();
            param += key + "=" + paramMap.get(key) + "&";
        }

        try {
            URL realUrl = new URL(wechatToken.getRequestUrl());
            // 打开和URL之间的连接
            URLConnection conn = realUrl.openConnection();
            // 设置通用的请求属性
            conn.setRequestProperty("accept", "*/*");
            conn.setRequestProperty("connection", "Keep-Alive");
            conn.setRequestProperty("Accept-Charset", "utf-8");
            conn.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
            // 发送POST请求必须设置如下两行
            conn.setDoOutput(true);
            conn.setDoInput(true);
            // 获取URLConnection对象对应的输出流
            out = new PrintWriter(conn.getOutputStream());
            // 发送请求参数
            out.print(param);
            // flush输出流的缓冲
            out.flush();
            // 定义BufferedReader输入流来读取URL的响应
            in = new BufferedReader(new InputStreamReader(conn.getInputStream(), "UTF-8"));
            String line;
            while ((line = in.readLine()) != null) {
                result += line;
            }
        } catch (Exception e) {
//            log.error(e.getMessage(), e);
            e.printStackTrace();
        }
        //使用finally块来关闭输出流、输入流
        finally {
            try {
                if (out != null) {
                    out.close();
                }
                if (in != null) {
                    in.close();
                }
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
        return JSON.parseObject(result).getString("openid");
    }

2. 发送模板消息

public class WechatMouldUtil {

    //token请求的方法
    private static String sendGet(String url, String param) {
        String result = "";
        BufferedReader in = null;
        try {
            String urlNameString = url + "?" + param;
            URL realUrl = new URL(urlNameString);
            // 打开和URL之间的连接
            URLConnection connection = realUrl.openConnection();
            // 设置通用的请求属性
            connection.setRequestProperty("accept", "*/*");
            connection.setRequestProperty("connection", "Keep-Alive");
            connection.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
            // 建立实际的连接
            connection.connect();
            // 获取所有响应头字段
//            Map<String, List<String>> map = connection.getHeaderFields();
            // 遍历所有的响应头字段
//            for (String key : map.keySet()) {
            // System.out.println(key + "--->" + map.get(key));
//            }
            // 定义 BufferedReader输入流来读取URL的响应
            in = new BufferedReader(new InputStreamReader(connection.getInputStream(), "utf-8"));
            // in = new BufferedReader(new
            // InputStreamReader(connection.getInputStream()));
            String line;
            while ((line = in.readLine()) != null) {
                result += line;
            }
        } catch (Exception e) {
            System.out.println("发送GET请求出现异常！" + e);
            e.printStackTrace();
        }
        // 使用finally块来关闭输入流
        finally {
            try {
                if (in != null) {
                    in.close();
                }
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }
        return result;

    }

    //获取token
    private static String getTokon() {
        WechatToken wechatToken = new WechatToken();
        // 小程序唯一标识
        String wxspAppid = wechatToken.getAppId();
        // 小程序的 app secret
        String wxspSecret = wechatToken.getAppSecret();
        //这里直接写死就可以，不用改，用法可以去看api
        String grant_type = "client_credential";
        //封装请求数据
        String params = "grant_type=" + grant_type + "&secret=" + wxspSecret + "&appid=" + wxspAppid;
        //发送GET请求
        String sendGet = sendGet("https://api.weixin.qq.com/cgi-bin/token", params);
        // 解析相应内容（转换成json对象）
        JSONObject json = new JSONObject(sendGet);
        //拿到accesstoken
        return json.get("access_token").toString();
    }

    //发送模板信息
    public String sendWechatmsgToUser(JSONObject data, String openid, String formId) {
        final String TEMPLATE_URL = "https://api.weixin.qq.com/cgi-bin/message/subscribe/send?access_token=ACCESS_TOKEN";
        String url = TEMPLATE_URL.replace("ACCESS_TOKEN", getTokon());
        JSONObject json = new JSONObject();
        WxTemplateid wxTemplateid = new WxTemplateid();
        try {

            json.put("template_id", wxTemplateid.getTemplateid());
            json.put("touser", openid);
            json.put("form_id", formId);
            json.put("data", data);

            String result = httpsRequest(url, "POST", json.toString());

            JSONObject resultJson = new JSONObject(result);
            String errmsg = (String) resultJson.get("errmsg");
            if (!"ok".equals(errmsg)) {//如果为errmsg为ok，则代表发送成功。
                return "error";
            }
        } catch (Exception e) {
            System.out.println("json数据出错");
            return "error";

        }
        return "success";
    }

    //    模板信息的请求方式
    private static String httpsRequest(String requestUrl, String requestMethod, String outputStr) {
        try {
            URL url = new URL(requestUrl);
            HttpsURLConnection conn = (HttpsURLConnection) url.openConnection();
            conn.setDoOutput(true);
            conn.setDoInput(true);
            conn.setUseCaches(false);
            // 设置请求方式（GET/POST）
            conn.setRequestMethod(requestMethod);
            conn.setRequestProperty("content-type", "application/x-www-form-urlencoded");
            // 当outputStr不为null时向输出流写数据
            if (null != outputStr) {
                OutputStream outputStream = conn.getOutputStream();
                // 注意编码格式
                outputStream.write(outputStr.getBytes("UTF-8"));
                outputStream.close();
            }
            // 从输入流读取返回内容
            InputStream inputStream = conn.getInputStream();
            InputStreamReader inputStreamReader = new InputStreamReader(inputStream, "utf-8");
            BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
            String str = null;
            StringBuffer buffer = new StringBuffer();
            while ((str = bufferedReader.readLine()) != null) {
                buffer.append(str);
            }
            // 释放资源
            bufferedReader.close();
            inputStreamReader.close();
            inputStream.close();
            conn.disconnect();
            return buffer.toString();
        } catch (ConnectException ce) {
            System.out.println("连接超时");
        } catch (Exception e) {
            System.out.println("https请求异常");

        }
        return null;
    }
}