因此我们必须去获取openid，同时也可以处理一些我们需要的逻辑。获取用户授权有两种方式:1.scope=snsapi_base;2.scope=snsapi_userinfo.我使用的是snsapi_base  //具体可参照官方文档

Scope为snsapi_base

https://open.weixin.qq.com/connect/oauth2/authorize?appid=wxf4bd796d62cb1bb5&redirect_uri=http://www.muguaerp.com/mcc/mobile/shop/product/pay.jhtml&response_type=code&scope=snsapi_userinfo&state=STATE#wechat_redirect

注意：这是发起支付前的操作。这里的 redirect_uri需要填写你要发起支付的页面

参数详解：

首先appid就不多说了就是你微信公众号的appid固定写死的，redirect_uri这个参数是最重要的，这个地址是访问你处理的接口地址。你可以在这个链接上拼接上你所需要的参数，一般你是要把订单的金额传到这个接口里的，访问这个链接的时候微信会给你code你需要用它去获取openid，记得要对其进行urlencode处理。state参数可以理解为扩展字段，其他的参数都是固定写法就不在多做介绍了。下面是获取openid的代码片段。
//第1步 获取openId

  HttpClientUtil util = HttpClientUtil.getInstance();Map<String, String> map = new HashMap<String, String>();map.put("appid", Configure.getAppid());map.put("secret",Configure.getAppsecret());map.put("code", code);map.put("grant_type", Configure.getGrant_type());String returnStr = util.getResponseBodyAsString("https://api.weixin.qq.com/sns/oauth2/access_token", map);AccessToken at = JSON.parseObject(returnStr, AccessToken.class);System.out.println(at);

//工具类
AccessToken.javapublic class AccessToken {private String access_token;private String expires_in;private String refresh_token;private String openid;private String scope;private String unionid;public String getAccess_token() {return access_token;}public void setAccess_token(String access_token) {this.access_token = access_token;}public String getExpires_in() {return expires_in;}public void setExpires_in(String expires_in) {this.expires_in = expires_in;}public String getRefresh_token() {return refresh_token;}public void setRefresh_token(String refresh_token) {this.refresh_token = refresh_token;}public String getOpenid() {return openid;}public void setOpenid(String openid) {this.openid = openid;}public String getScope() {return scope;}public void setScope(String scope) {this.scope = scope;}public String getUnionid() {return unionid;}public void setUnionid(String unionid) {this.unionid = unionid;}@Overridepublic String toString() {return "AccessToken [access_token=" + access_token + ", expires_in="+ expires_in + ", refresh_token=" + refresh_token + ", openid="+ openid + ", scope=" + scope + ", unionid=" + unionid + "]";}}

二、    我们获取了openid后，就可以进行下一步的统一下单的开发了。微信上统一下单接口的文档写的比较详细了，具体的参数含义我就不多做介绍了。下面直接贴最直观的代码，特别提醒的是一定要注意签名的正确。签名所使用的key并不是AppSecret而是你申请时自己定义的商户key。

//第2步 统一下单

 String strAttach = "微信支付";//strAttach = new String(strAttach.getBytes("gbk"),"utf-8");String strBody = "微信公众号支付";//strBody = new String(strBody.getBytes("gbk"),"utf-8");Order order= orderService.findBySn(sn);String ip = request.getRemoteAddr();WxPaySendData data = new WxPaySendData();data.setAppid(Configure.getAppid());data.setAttach(URLEncoder.encode(strAttach, "UTF-8"));data.setBody(URLEncoder.encode(strBody, "UTF-8"));data.setMch_id(Configure.getMchid());data.setNonce_str(RandomStringGenerator.getRandomStringByLength(32));data.setNotify_url(Configure.getNotify_url());data.setOut_trade_no(UtilDate.getOrderNum());data.setTotal_fee((order.getAmount().multiply(new BigDecimal(100)).intValue()));//单位：分data.setTrade_type("JSAPI");data.setSpbill_create_ip(ip);data.setOpenid(at.getOpenid());String returnXml = UnifiedorderService.unifiedOrder(data,Configure.getKey());WxPayReturnData reData = new WxPayReturnData();XStream xs1 = new XStream(new DomDriver());xs1.alias("xml", WxPayReturnData.class);reData = (WxPayReturnData) xs1.fromXML(returnXml);

注意：这里腾讯用的是xml格式的参数因此需要把参数转成xml格式。这里用的是XStream，并且需要把sendData 和 returnData 封装成class

//工具类
UnifiedorderService.java
public class UnifiedorderService {private final static Logger logger = LoggerFactory.getLogger(UnifiedorderService.class);public static String unifiedOrder(WxPaySendData data,String key){//统一下单支付String returnXml = null;try {//生成sign签名SortedMap<Object,Object> parameters = new TreeMap<Object,Object>();parameters.put("appid", data.getAppid()); parameters.put("attach", data.getAttach());parameters.put("body", data.getBody());parameters.put("mch_id", data.getMch_id());parameters.put("nonce_str", data.getNonce_str());parameters.put("notify_url", data.getNotify_url());parameters.put("out_trade_no", data.getOut_trade_no());parameters.put("total_fee", data.getTotal_fee());parameters.put("trade_type", data.getTrade_type());parameters.put("spbill_create_ip", data.getSpbill_create_ip());parameters.put("openid", data.getOpenid());parameters.put("device_info", data.getDevice_info());logger.info("SIGN:"+WxSign.createSign(parameters,key));data.setSign(WxSign.createSign(parameters,key));XStream xs = new XStream(new DomDriver("UTF-8",new XmlFriendlyNameCoder("-_", "_")));xs.alias("xml", WxPaySendData.class);String xml = xs.toXML(data);logger.info("统一下单xml为:\n" + xml);HttpClientUtil util = HttpClientUtil.getInstance();returnXml = util.doPostForString("https://api.mch.weixin.qq.com/pay/unifiedorder", null, xml);logger.info("返回结果:" + returnXml);} catch (Exception e) {e.printStackTrace();} return returnXml;}}

//工具类
WxSign.java
public class WxSign {private static String characterEncoding = "UTF-8";@SuppressWarnings("rawtypes")public static String createSign(SortedMap<Object,Object> parameters,String key){ StringBuffer sb = new StringBuffer(); Set es = parameters.entrySet();//所有参与传参的参数按照accsii排序（升序） Iterator it = es.iterator(); while(it.hasNext()) { Map.Entry entry = (Map.Entry)it.next(); String k = (String)entry.getKey(); Object v = entry.getValue(); if(null != v && !"".equals(v)  && !"sign".equals(k) && !"key".equals(k)) { sb.append(k + "=" + v + "&"); } } sb.append("key=" + key);String sign = MD5.MD5Encode(sb.toString(), characterEncoding).toUpperCase(); return sign; }public static String getNonceStr() {Random random = new Random();return MD5Util.MD5Encode(String.valueOf(random.nextInt(10000)), "UTF-8");}public static String getTimeStamp() {return String.valueOf(System.currentTimeMillis() / 1000);}}

//md5.java
package com.pawpaw.plugin.tencentpay;import java.security.MessageDigest;/**
* User: rizenguo
* Date: 2014/10/23
* Time: 15:43
*/
public class MD5 {private final static String[] hexDigits = {"0", "1", "2", "3", "4", "5", "6", "7","8", "9", "a", "b", "c", "d", "e", "f"};/*** 转换字节数组为16进制字串* @param b 字节数组* @return 16进制字串*/public static String byteArrayToHexString(byte[] b) {StringBuilder resultSb = new StringBuilder();for (byte aB : b) {resultSb.append(byteToHexString(aB));}return resultSb.toString();}/*** 转换byte到16进制* @param b 要转换的byte* @return 16进制格式*/private static String byteToHexString(byte b) {int n = b;if (n < 0) {n = 256 + n;}int d1 = n / 16;int d2 = n % 16;return hexDigits[d1] + hexDigits[d2];}/*** MD5编码* @param origin 原始字符串* @return 经过MD5加密之后的结果*/public static String MD5Encode(String origin) {String resultString = null;try {resultString = origin;MessageDigest md = MessageDigest.getInstance("MD5");resultString = byteArrayToHexString(md.digest(resultString.getBytes()));} catch (Exception e) {e.printStackTrace();}return resultString;}}

//WxPaySendData.java
package com.pawpaw.entity;public class WxPaySendData {//公众号IDprivate String appid;//附加参数private String attach;//商品名称private String body;//商户IDprivate String mch_id;//随机支付串private String nonce_str;//通知地址,不能携带参数,直接就能访问private String notify_url;//用户订单号private String out_trade_no;//总金额 以分为单位private int total_fee;//交易类型private String trade_type;//终端IPprivate String spbill_create_ip;//openIDprivate String openid;//签名private String sign;public String getAppid() {return appid;}public void setAppid(String appid) {this.appid = appid;}public String getAttach() {return attach;}public void setAttach(String attach) {this.attach = attach;}public String getBody() {return body;}public void setBody(String body) {this.body = body;}public String getMch_id() {return mch_id;}public void setMch_id(String mch_id) {this.mch_id = mch_id;}public String getNonce_str() {return nonce_str;}public void setNonce_str(String nonce_str) {this.nonce_str = nonce_str;}public String getNotify_url() {return notify_url;}public void setNotify_url(String notify_url) {this.notify_url = notify_url;}public String getOut_trade_no() {return out_trade_no;}public void setOut_trade_no(String out_trade_no) {this.out_trade_no = out_trade_no;}public int getTotal_fee() {return total_fee;}public void setTotal_fee(int total_fee) {this.total_fee = total_fee;}public String getTrade_type() {return trade_type;}public void setTrade_type(String trade_type) {this.trade_type = trade_type;}public String getSpbill_create_ip() {return spbill_create_ip;}public void setSpbill_create_ip(String spbill_create_ip) {this.spbill_create_ip = spbill_create_ip;}public String getOpenid() {return openid;}public void setOpenid(String openid) {this.openid = openid;}public String getSign() {return sign;}public void setSign(String sign) {this.sign = sign;}}

//WxPayReturnData.java
package com.pawpaw.entity;public class WxPayReturnData {//业务结果private String return_code;//消息private String return_msg;//公众号IDprivate String appid;//商户IDprivate String mch_id;//随机支付串private String nonce_str;//签名private String sign;//业务结果private String result_code;//预支付IDprivate String prepay_id;//交易类型private String trade_type;public String getReturn_code() {return return_code;}public void setReturn_code(String return_code) {this.return_code = return_code;}public String getReturn_msg() {return return_msg;}public void setReturn_msg(String return_msg) {this.return_msg = return_msg;}public String getAppid() {return appid;}public void setAppid(String appid) {this.appid = appid;}public String getMch_id() {return mch_id;}public void setMch_id(String mch_id) {this.mch_id = mch_id;}public String getNonce_str() {return nonce_str;}public void setNonce_str(String nonce_str) {this.nonce_str = nonce_str;}public String getSign() {return sign;}public void setSign(String sign) {this.sign = sign;}public String getResult_code() {return result_code;}public void setResult_code(String result_code) {this.result_code = result_code;}public String getPrepay_id() {return prepay_id;}public void setPrepay_id(String prepay_id) {this.prepay_id = prepay_id;}public String getTrade_type() {return trade_type;}public void setTrade_type(String trade_type) {this.trade_type = trade_type;}}

最后要提一下的是NOTIFY_URL回调地址，接收微信支付异步通知回调地址。

三    通过上面的操作我们获得了预支付交易会话标识prepay_id，这样我们就可以进行最后一步的操作了。使用H5调起支付api。

//第3步 数据传到前端，H5调起支付

  model.addAttribute("appId", reData.getAppid());model.addAttribute("timeStamp", Wxsign.getTimeStamp());model.addAttribute("nonceStr", reData.getNonce_str());model.addAttribute("Package", "prepay_id="+reData.getPrepay_id());model.addAttribute("signType", "MD5");SortedMap<Object,Object> signMap = new TreeMap<Object,Object>();signMap.put("appId", reData.getAppid()); signMap.put("timeStamp", Wxsign.getTimeStamp());signMap.put("nonceStr", reData.getNonce_str());signMap.put("package", "prepay_id="+ reData.getPrepay_id());signMap.put("signType", "MD5");model.addAttribute("paySign", Wxsign.createSign(signMap,Configure.getKey()));model.addAttribute("numb", order.getSn());model.addAttribute("order", order);

将需要的参数传给页面后，使用微信提供方法调起支付。

<script type="text/javascript">
$(function(){
//这里是调用微信内置浏览器的微信支付
$("#anniu_z").click(function(){
callPay();
});function onBridgeReady() {WeixinJSBridge.invoke('getBrandWCPayRequest', {"appId" : "${appId}",//"wx2421b1c4370ec43b", //公众号名称，由商户传入   "timeStamp" : "${timeStamp}",//"1395712654", //时间戳，自1970年以来的秒数   "nonceStr" : "${nonceStr}",//"e61463f8efa94090b1f366cccfbbb444", //随机串   "package" : "${Package}",//"prepay_id=u802345jgfjsdfgsdg888","signType" : "${signType}",//"MD5", //微信签名方式:   "paySign" : "${paySign}"//"70EA570631E4BB79628FBCA90534C63FF7FADD89" //微信签名 }, function(res) { // 使用以上方式判断前端返回,微信团队郑重提示：res.err_msg将在用户支付成功后返回  ok，但并不保证它绝对可靠。  //alert(res.err_msg);if (res.err_msg == "get_brand_wcpay_request:ok") {//alert("支付成功");//这里是商品入库$.ajax({url:'${base}/mobile/shop/product/returnPay.jhtml',type:'post',dataType:'json',success:function(message){$.message(message);if("${productCategory.name}"=="教育文库"){setTimeout('location.href="${base}/mobile/shop/product/searchWord.jhtml?id=${product.id}"',3000);}else {setTimeout('location.href="${base}/mobile/shop/product/search.jhtml?id=${product.id}"',3000);}}});                }if (res.err_msg == "get_brand_wcpay_request:cancel") {alert("交易取消");}if (res.err_msg == "get_brand_wcpay_request:fail") {alert("支付失败");}});}function callPay() {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();}}});
</script>

补充一下：微信公众号开发用到的所有工具类