调用微信现金红包接口发放红包

1.通过code获取到用户的openid.

引导用户到指定的授权页面

例如：https://open.weixin.qq.com/connect/oauth2/authorize?appid=APPID&redirect_uri=redirect_uri&response_type=code&scope=SCOPE&state=STATE#wechat_redirect

参考文章：http://www.cnblogs.com/ansiboy/p/3755158.html

redirect_uri  为微信调用地址，返回code,然后用code通过下面的地址去换取openid

地址： "https://api.weixin.qq.com/sns/oauth2/access_token?appid=wxid&secret=secret&code="
            + code + "&grant_type=authorization_code";

公众号需获取网页授权获取用户基本信息权限。

2.通过openid及用户相关信息向用户发放红包。

      地址："https://api.mch.weixin.qq.com/mmpaymkttransfers/sendredpack"

需要发放商户号用户openid等相关信息，需要注意的是签名信息与随机字符串

代码如下：

1. public static String createSendRedPackOrderSign(WeixinRedPacket redPack){
            StringBuffer sign = new StringBuffer();
            sign.append("act_name=").append(redPack.getAct_name());
            sign.append("&client_ip=").append(redPack.getClient_ip());
            sign.append("&mch_billno=").append(redPack.getMch_billno());
            sign.append("&mch_id=").append(redPack.getMch_id());
            sign.append("&nonce_str=").append(redPack.getNonce_str());
            sign.append("&re_openid=").append(redPack.getRe_openid());
            sign.append("&remark=").append(redPack.getRemark());
            sign.append("&send_name=").append(redPack.getSend_name());
            sign.append("&total_amount=").append(redPack.getTotal_amount());
            sign.append("&total_num=").append(redPack.getTotal_num());
            sign.append("&wishing=").append(redPack.getWishing());
            sign.append("&wxappid=").append(redPack.getWxappid());
            sign.append("&key=").append("abcdefg123456789abcdefg123456789");
            return DigestUtils.md5Hex(getContentBytes(sign.toString(), "utf-8")).toUpperCase();
        }
      private static String create_nonce_str() {
            return UUID.randomUUID().toString();
        }

2.需要注意上传证书及将所有信息发放给微信，这里还需要使用微信给出的开发包，在微信上下载即可。

 Map<String ,String> maps =  new HashMap<String, String>();
           //分享任务完成后，调用发红包接口，需要传入商户订单号，openid,发放金额三个参数
           WeixinRedPacket bean = new WeixinRedPacket();  
           bean.setNonce_str(create_nonce_str().substring(0, 31));  
           bean.setMch_billno(mch_billno);  
           bean.setMch_id(PayConst.WX_MCH_ID);  
           bean.setWxappid(PayConst.WX_APPID);  
           bean.setSend_name(PayConst.WX_SEND_NAME);  
           bean.setRe_openid(openid);  
           bean.setTotal_amount(amount);//金额分  
           bean.setTotal_num(PayConst.WX_TOTAL_NUM);//发送人数  
           bean.setWishing(PayConst.WX_WISHING);  
           bean.setClient_ip(PayConst.WX_CLIENT_IP);  
           bean.setAct_name(PayConst.WX_ACT_NAME);  
           bean.setRemark(PayConst.WX_REMARK);       
           bean.setSign(createSendRedPackOrderSign(bean)); 

           String requestJson = "<xml>"
               +"<sign><![CDATA[" + bean.getSign() + "]]></sign>"
               +"<mch_billno><![CDATA[" + bean.getMch_billno() + "]]></mch_billno>"
               +"<mch_id><![CDATA[" + bean.getMch_id() + "]]></mch_id>"
               +"<wxappid><![CDATA[" + bean.getWxappid() + "]]></wxappid>"
               +"<send_name><![CDATA["+ bean.getSend_name() +"]]></send_name>"
               +"<re_openid><![CDATA[" + bean.getRe_openid() + "]]></re_openid>"
               +"<total_amount><![CDATA[" + bean.getTotal_amount() + "]]></total_amount>"
               +"<total_num><![CDATA[" + bean.getTotal_num() + "]]></total_num>"
               +"<wishing><![CDATA[" + bean.getWishing() + "]]></wishing>"
               +"<client_ip><![CDATA[" + bean.getClient_ip() + "]]></client_ip>"
               +"<act_name><![CDATA[" + bean.getAct_name() + "]]></act_name>"
               +"<remark><![CDATA[" + bean.getRemark() + "]]></remark>"
               +"<nonce_str><![CDATA[" + bean.getNonce_str() + "]]></nonce_str>"
               +"</xml>";
           KeyStore keyStore  = KeyStore.getInstance("PKCS12");
           FileInputStream instream = new FileInputStream(new File("D:\certs\apiclient_cert.p12"));
           try {
               keyStore.load(instream, "123".toCharArray());//123为商户号
           } finally {
               instream.close();
           }

           // Trust own CA and all self-signed certs
           SSLContext sslcontext = SSLContexts.custom()
                   .loadKeyMaterial(keyStore, "123".toCharArray())
                   .build();
           // Allow TLSv1 protocol only
           SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(
                   sslcontext,
                   new String[] { "TLSv1" },
                   null,
                   SSLConnectionSocketFactory.BROWSER_COMPATIBLE_HOSTNAME_VERIFIER);
           CloseableHttpClient httpclient = HttpClients.custom()
                   .setSSLSocketFactory(sslsf)
                   .build();
           try {

               HttpPost httppost = new HttpPost("https://api.mch.weixin.qq.com/mmpaymkttransfers/sendredpack");
               StringEntity s = new StringEntity(requestJson,"UTF-8");
               s.setContentEncoding("UTF-8");
               s.setContentType("text/xml");//发送json数据需要设置contentType
               httppost.setEntity(s);
               CloseableHttpResponse resp = httpclient.execute(httppost);
               try {
                   HttpEntity entity = resp.getEntity();

                   if (entity != null) {
                       BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(entity.getContent(),"utf-8"));
                       String text;
                       String xmlString = "";
                       while ((text = bufferedReader.readLine()) != null) {
                           xmlString += text;
                       }
                       
                       //return_code与result_code都为success代表发放红包成功
                       maps = XmlParseUtil.parse(xmlString);
                   }
                   EntityUtils.consume(entity);
               } finally {
                   resp.close();
               }
           } finally {
               httpclient.close();
           }

微信官方文档地址：https://pay.weixin.qq.com/helper/cashredopenapi_V2.pdf