1. 首先微信支付需要以下的字段,关于如何去获取微信支付的字段，网上一大把，注意（像商户号等重要字段不要泄露不要泄露）

1. MCHID(商户号) 就是商户注册之后，微信支付给你的唯一的数字

1. APPID(小程序的appid)

1. SSLFILE(微信支付需要申请证书，这个字段就是把申请的证书下载之后，存放在你服务器的某个文件夹的路径）

1. NOTIFYURL(支付成功之后，微信会给你这个url发送一条支付成功的消息)

1. APIKEY(证书的秘钥)

需要微信支付的jar包

     <dependency><groupId>com.github.wxpay</groupId><artifactId>wxpay-sdk</artifactId><version>0.0.3</version></dependency><dependency><groupId>com.github.binarywang</groupId><artifactId>weixin-java-pay</artifactId><version>3.8.0</version></dependency><dependency><groupId>com.github.wechatpay-apiv3</groupId><artifactId>wechatpay-apache-httpclient</artifactId><version>0.4.7</version></dependency>

2.开始微信支付的demo，首先看微信支付调用支付需要那些必传字段(注意顺序),可以通过这个地址查看https://pay.weixin.qq.com/wiki/doc/api/jsapi.php?chapter=9_1

3.关于签名加密的方法(后续也会使用到)

public class MD5Util {private static final String hexDigits[] = { "0", "1", "2", "3", "4", "5","6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };public static String byteArrayToHexString(byte b[]) {StringBuffer resultSb = new StringBuffer();for (int i = 0; i < b.length; i++)resultSb.append(byteToHexString(b[i]));return resultSb.toString();}private static String byteToHexString(byte b) {int n = b;if (n < 0)n += 256;int d1 = n / 16;int d2 = n % 16;return hexDigits[d1] + hexDigits[d2];}public static String MD5Encode(String origin ) {return MD5Encode(origin,null);}public static String MD5Encode(String origin, String charsetname) {String resultString = null;try {resultString = new String(origin);MessageDigest md = MessageDigest.getInstance("MD5");if (charsetname == null || "".equals(charsetname))resultString = byteArrayToHexString(md.digest(resultString.getBytes()));elseresultString = byteArrayToHexString(md.digest(resultString.getBytes(charsetname)));} catch (Exception exception) {}return resultString;}}

4.将集合的数据进行xml处理

public static String getRequest(TreeMap<String, String> parameters)throws Exception {  //StringBuffer sb = new StringBuffer();sb.append("<xml>");Set es = parameters.entrySet();Iterator it = es.iterator();while (it.hasNext()) {Map.Entry entry = (Map.Entry) it.next();String k = (String) entry.getKey();String v = (String) entry.getValue();if ("mch_id".equalsIgnoreCase(k) || "nonce_str".equalsIgnoreCase(k)|| "sign".equalsIgnoreCase(k)) {sb.append("<" + k + ">" + "<![CDATA[" + v + "]]></" + k + ">");} else {sb.append("<" + k + ">" + v + "</" + k + ">");}}sb.append("</xml>");return sb.toString();}

5.将加密的数据通过url发送给微信支付，成功之后微信支付会将需要的数据返回给你，这里的url是：

6.将微信支付返回的xml数据解析成集合，然后通过集合的key获取到值组装发给前端，大致流程就是这样的了。

  //xml解析public static TreeMap doXMLParse(String strxml) throws JDOMException, IOException {strxml = strxml.replaceFirst("encoding=\".*\"", "encoding=\"UTF-8\"");if(null == strxml || "".equals(strxml)) {return null;}TreeMap m = new TreeMap();InputStream in = new ByteArrayInputStream(strxml.getBytes("UTF-8"));SAXBuilder builder = new SAXBuilder();Document doc = builder.build(in);Element root = doc.getRootElement();List list = root.getChildren();Iterator it = list.iterator();while(it.hasNext()) {Element e = (Element) it.next();String k = e.getName();String v = "";List children = e.getChildren();if(children.isEmpty()) {v = e.getTextNormalize();} else {v = getChildrenText(children);}m.put(k, v);}//关闭流in.close();return m;}public static String getChildrenText(List children) {StringBuffer sb = new StringBuffer();if(!children.isEmpty()) {Iterator it = children.iterator();while(it.hasNext()) {Element e = (Element) it.next();String name = e.getName();String value = e.getTextNormalize();List list = e.getChildren();sb.append("<" + name + ">");if(!list.isEmpty()) {sb.append(getChildrenText(list));}sb.append(value);sb.append("</" + name + ">");}}return sb.toString();}

7.后续将字段返回给前端之后，前端进行调用，微信支付成功之后，会将支付回调返回给你controller里面的方法,支付成功之后里面进行业务逻辑处理.

总结：关于V2版本的微信支付的难点主要是在于对xml进行解析，以及对证书的验证处理的方法,后续会出支付宝支付的流程，请大家关注我，不会让大家失望的。