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

code作为换取access_token的票据，每次用户授权带上的code将不一样，code只能使用一次，5分钟未被使用自动过期。

https://api.weixin.qq.com/sns/oauth2/access_token?appid=APPID&secret=SECRET&code=CODE&grant_type=authorization_code

{"errcode":40029,"errmsg":"invalid code"}

<dependency>
    <groupId>com.github.tedzhdz</groupId>
    <artifactId>wxpay-sdk</artifactId>
    <version>3.0.10</version>
</dependency>

<dependency>
    <groupId>com.github.binarywang</groupId>
    <artifactId>weixin-java-pay</artifactId>
    <version>3.4.0</version>
</dependency>

String appID = "wxd2bf2dba2e86a8c7";
String mchID = "1502570431";
String appSecret = "cec1a9185ad435abe1bced4b93f7ef2e";
String key = "95fe355daca50f1ae82f0865c2ce87c8";
//申请授权码地址
String wxOAuth2RequestUrl = "https://open.weixin.qq.com/connect/oauth2/authorize";
//授权回调地址，此域名为前边设置的微信网页授权域名
String wxOAuth2CodeReturnUrl = "http://xfc.nat300.top/transaction/wx-oauth-code-return-test";

@Slf4j
@Controller
public class WxPayController {

    String appID = "wxd2bf2dba2e86a8c7";
    String mchID = "1502570431";
    String appSecret = "cec1a9185ad435abe1bced4b93f7ef2e";
    String key = "95fe355daca50f1ae82f0865c2ce87c8";
    //申请授权码地址
    String wxOAuth2RequestUrl = "https://open.weixin.qq.com/connect/oauth2/authorize";
    //授权回调地址
    String wxOAuth2CodeReturnUrl = "http://xfc.nat300.top/transaction/wx-oauth-code-return";
	String state="";
@GetMapping("/getWXOAuth2Code")
public String getWXOAuth2Code(HttpServletRequest httpRequest, HttpServletResponse httpResponse) throws IOException {
	//  https://open.weixin.qq.com/connect/oauth2/authorize?appid=APPID&redirect_uri=REDIRECT_URI&response_type=code&scope=SCOPE&state=STATE#wechat_redirect
    String url = String
            .format("%s?appid=%s&scope=snsapi_base&state=%s&redirect_uri=%s", wxOAuth2RequestUrl, appID,
                    state, URLEncoder.encode(wxOAuth2CodeReturnUrl, "utf-8"));
    return "redirect:" + url;
}
}

//授权通过跳转到 /wx-oauth-code-return-test?code=CODE&state=STATE。
@GetMapping("/wx-oauth-code-return-test")
public String wxOAuth2CodeReturn(@RequestParam String code, @RequestParam String state) {
//https://api.weixin.qq.com/sns/oauth2/access_token?appid=APPID&secret=SECRET&code=CODE&grant_type=authorization_code
 //申请openid
 String tokenUrl = String
                .format("https://api.weixin.qq.com/sns/oauth2/access_token?appid=%s&secret=%s&code=%s&grant_type=authorization_code", appID, appSecret,code, "utf-8");

        ResponseEntity<String> exchange = new RestTemplate().exchange(tokenUrl, HttpMethod.GET, null, String.class);
        String response = exchange.getBody();
        String openid= JSONObject.parseObject(response).getString("openid");
		//携带openid跳转至统一下单地址
        return "redirect:http://xfc.nat300.top/transaction/wxjspay?openid=" + openid;
}

http://192.168.159.1:56050/transaction/getWXOAuth2Code

URL地址：https://api.mch.weixin.qq.com/pay/unifiedorder

function onBridgeReady(){
   WeixinJSBridge.invoke(
      'getBrandWCPayRequest', {
         "appId":"wx2421b1c4370ec43b",     //公众号名称，由商户传入     
         "timeStamp":"1395712654",         //时间戳，自1970年以来的秒数     
         "nonceStr":"e61463f8efa94090b1f366cccfbbb444", //随机串     
         "package":"prepay_id=u802345jgfjsdfgsdg888",     
         "signType":"MD5",         //微信签名方式：     
         "paySign":"70EA570631E4BB79628FBCA90534C63FF7FADD89" //微信签名 
      },
      function(res){
      if(res.err_msg == "get_brand_wcpay_request:ok" ){
      // 使用以上方式判断前端返回,微信团队郑重提示：
            //res.err_msg将在用户支付成功后返回ok，但并不保证它绝对可靠。
      } 
   }); 
}
if (typeof WeixinJSBridge == "undefined"){
   if( document.addEventListener ){
       document.addEventListener('WeixinJSBridgeReady', onBridgeReady, false);
   }else if (document.attachEvent){
       document.attachEvent('WeixinJSBridgeReady', onBridgeReady); 
       document.attachEvent('onWeixinJSBridgeReady', onBridgeReady);
   }
}else{
   onBridgeReady();
}

public class WXPayConfigCustom extends WXPayConfig{

    @Override
    protected String getAppID() {
        return appID;
    }

    @Override
    protected String getMchID() {
        return mchID;
    }

    @Override
    protected String getKey() {
        return key;
    }

    @Override
    protected InputStream getCertStream() {
        return null;
    }

    @Override
    protected IWXPayDomain getWXPayDomain() {
        return new IWXPayDomain() {
            @Override
            public void report(String s, long l, Exception e) {

            }
            @Override
            public DomainInfo getDomain(WXPayConfig wxPayConfig) {//api.mch.weixin.qq.com
                return new DomainInfo(WXPayConstants.DOMAIN_API, true);
            }
        };
    }
}

 //微信统一下单
    @RequestMapping("/wxjspay")
    public ModelAndView wxjspay(HttpServletRequest request, HttpServletResponse response) throws Exception {
        try {

            //微信支付渠道参数
            WXPay wxpay = new WXPay(new WXPayConfigCustom());

            //按照微信统一下单接口要求构造请求参数
            //https://pay.weixin.qq.com/wiki/doc/api/jsapi.php?chapter=9_1
            Map<String, String> requestParam = new HashMap<String, String>();
            requestParam.put("body", "iphone8");//订单描述
            requestParam.put("out_trade_no", "1234567");//订单号
            requestParam.put("fee_type", "CNY");//人民币
            requestParam.put("total_fee", String.valueOf(1)); //金额
            requestParam.put("spbill_create_ip", "127.0.0.1");//客户端ip
            requestParam.put("notify_url", "none");//微信异步通知支付结果接口，暂时不用
            requestParam.put("trade_type", "JSAPI");
            requestParam.put("openid", request.getParameter("openid"));

            //调用微信统一下单API
            Map<String, String> resp = wxpay.unifiedOrder(requestParam);

            //根据返回预付单信息生成JSAPI页面调用的支付参数并签名
            String timestamp = String.valueOf(System.currentTimeMillis() / 1000);
            Map<String, String> jsapiPayParam = new HashMap<>();
            jsapiPayParam.put("appId", resp.get("appid"));
            jsapiPayParam.put("package", "prepay_id=" + resp.get("prepay_id"));
            jsapiPayParam.put("timeStamp", timestamp);
            jsapiPayParam.put("nonceStr", UUID.randomUUID().toString());
            jsapiPayParam.put("signType", "HMAC-SHA256");
            jsapiPayParam.put("paySign",
                    WXPayUtil.generateSignature(jsapiPayParam, key, WXPayConstants.SignType.HMACSHA256));
            log.info("微信JSAPI支付响应内容：" + jsapiPayParam);

            return new ModelAndView("wxpay", jsapiPayParam);
        }catch (Exception e){
            e.printStackTrace();
        }
        return null;
    }

http://192.168.159.1:56010/transaction/getWXOAuth2Code