前面已經講過微信APP支付的統一下單、支付結果通知的介面開發，現在我們講述一下申請退款的流程開發。

1、應用場景

當交易發生之後一段時間內，由於買家或者賣家的原因需要退款時，賣家可以通過退款介面將支付款退還給買家，微信支付將在收到退款請求並且驗證成功之後，按照退款規則將支付款按原路退到買家帳號上。

注意：

1、交易時間超過一年的訂單無法提交退款；

2、微信支付退款支援單筆交易分多次退款，多次退款需要提交原支付訂單的商戶訂單號和設定不同的退款單號。申請退款總金額不能超過訂單金額。 一筆退款失敗後重新提交，請不要更換退款單號，請使用原商戶退款單號。

3、請求頻率限制：150qps，即每秒鐘正常的申請退款請求次數不超過150次

    錯誤或無效請求頻率限制：6qps，即每秒鐘異常或錯誤的退款申請請求不超過6次

4、每個支付訂單的部分退款次數不能超過50次

2、介面連結

介面連結：https://api.mch.weixin.qq.com/secapi/pay/refund

3、是否需要證書

請求需要雙向證書。 詳見證書使用

4、請求引數

5、程式碼實現

5.1基礎類

WeChatConfig配置類，主要包含微信的配置資訊

package com.hisap.xql.api.common.wechat;
 
/**
 * @Author: QijieLiu
 * @Description: 微信配置資訊
 * @Date: Created in 16:47 2018/8/14
 */
public class WeChatConfig {
	 public static String APP_ID = "xxxxxx";
	 public static String MCH_ID = "xxxxxx";
	 public static String MCH_KEY = "xxxxxx";
	 public static String APP_SECRET = "xxxxxx";
	 public static String UNIFIEDORDER_URL = "https://api.mch.weixin.qq.com/pay/unifiedorder";
	 public static String NOTIFY_URL = "http://xxx.xxx.xxx.xxx:8080/XqlApi/wechatpay/paynotify";
	 public static String REFUND_URL = "https://api.mch.weixin.qq.com/secapi/pay/refund";
	 public static String REFUND_NOTIFY_URL = "http://xxx.xxx.xxx.xxx:8080/XqlApi/wechatpay/refundnotify";
	 public static String TRADE_TYPE = "APP";
	 public static String CERT_URL="E:\\cert\\apiclient_cert.p12";
}

 ResponseJson基礎類，主要與APP前端進行互動

package com.hisap.xql.api.common.bean;
 
public class ResponseJson {
	// 結果碼
	private String code;
	// 結果說明
	private String message;
	// 內容
	private Object data;
 
	public String getCode() {
		return code;
	}
 
	public void setCode(String code) {
		this.code = code;
	}
 
	public String getMessage() {
		return message;
	}
 
	public void setMessage(String message) {
		this.message = message;
	}
 
	public Object getData() {
		return data;
	}
 
	public void setData(Object data) {
		this.data = data;
	}
 
}

5.2工具類

MD5Utils類

package com.hisap.xql.api.common.utils;
 
import java.security.MessageDigest;
 
/**
 * @Author: QijieLiu
 * @Description: MD5加密工具
 * @Date: Created in 09:39 2018/8/17
 */
public class MD5Utils {
	 
	public final static String MD5(String s) {
		char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
		try {
			byte[] btInput = s.getBytes();
			// 獲得MD5摘要演算法的 MessageDigest 物件
			MessageDigest mdInst = MessageDigest.getInstance("MD5");
			// 使用指定的位元組更新摘要
			mdInst.update(btInput);
			// 獲得密文
			byte[] md = mdInst.digest();
			// 把密文轉換成十六進位制的字串形式
			int j = md.length;
			char str[] = new char[j * 2];
			int k = 0;
			for (int i = 0; i < j; i++) {
				byte byte0 = md[i];
				str[k++] = hexDigits[byte0 >>> 4 & 0xf];
				str[k++] = hexDigits[byte0 & 0xf];
			}
			return new String(str);
		}
		catch (Exception e) {
			e.printStackTrace();
			return null;
		}
	}
 
	private 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, 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()));
			else
				resultString = byteArrayToHexString(md.digest(resultString.getBytes(charsetname)));
		}
		catch (Exception exception) {
		}
		return resultString;
	}
 
	private static final String hexDigits[] = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };
 
	public static void main(String[] asd) {
		String con = "hello kitty";
		String str = MD5Encode(con, "UTF-8");
		System.out.println(str.toUpperCase());
	}
}

CommonUtil類

package com.hisap.xql.api.common.wechat;
 
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.net.ConnectException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.security.KeyStore;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Random;
import java.util.Set;
import java.util.SortedMap;
import java.util.TreeMap;
 
import javax.net.ssl.SSLContext;
 
import org.apache.http.Consts;
import org.apache.http.HttpEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.ssl.SSLContexts;
import org.apache.http.util.EntityUtils;
import org.jdom.Document;
import org.jdom.Element;
import org.jdom.JDOMException;
import org.jdom.input.SAXBuilder;
 
import com.hisap.xql.api.common.utils.MD5Utils;
 
/**
 * @Author: QijieLiu
 * @Description: 微信支付工具類
 * @Date: Created in 19:39 2018/8/21
 */
public class CommonUtil {
	// 微信引數配置
	public static String API_KEY = WeChatConfig.MCH_KEY;
 
	// 隨機字串生成
	public static String getRandomString(int length) { // length表示生成字串的長度
		String base = "abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
		Random random = new Random();
		StringBuffer sb = new StringBuffer();
		for (int i = 0; i < length; i++) {
			int number = random.nextInt(base.length());
			sb.append(base.charAt(number));
		}
		return sb.toString();
	}
 
	// 請求xml組裝
	public static String getRequestXml(SortedMap<String, Object> parameters) {
		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 key = (String) entry.getKey();
			String value = entry.getValue().toString();
			if ("attach".equalsIgnoreCase(key) || "body".equalsIgnoreCase(key)
					|| "sign".equalsIgnoreCase(key)) {
				sb.append("<" + key + ">" + "<![CDATA[" + value + "]]></" + key
						+ ">");
			} else {
				sb.append("<" + key + ">" + value + "</" + key + ">");
			}
		}
		sb.append("</xml>");
		return sb.toString();
	}
 
	// 生成簽名
	public static String createSign(String characterEncoding,
			SortedMap<String, Object> parameters) {
		StringBuffer sb = new StringBuffer();
		Set es = parameters.entrySet();
		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=" + API_KEY);
		System.out.println(sb.toString());
		String sign = MD5Utils.MD5Encode(sb.toString(), characterEncoding)
				.toUpperCase();
		return sign;
	}
 
	/**
	 * 驗證回撥簽名
	 * 
	 * @param packageParams
	 * @param key
	 * @param charset
	 * @return
	 */
	public static boolean isTenpaySign(Map<String, String> map) throws UnsupportedEncodingException {
		String charset = "utf-8";
		String signFromAPIResponse = map.get("sign");
		if (signFromAPIResponse == null || signFromAPIResponse.equals("")) {
			System.out.println("API返回的資料簽名資料不存在，有可能被第三方篡改!!!");
			return false;
		}
		System.out.println("伺服器回包裡面的簽名是:" + signFromAPIResponse);
		// 過濾空 設定 TreeMap
		SortedMap<String, String> packageParams = new TreeMap<>();
		for (String parameter : map.keySet()) {
			String parameterValue = map.get(parameter);
			String v = "";
			if (null != parameterValue) {
				v = parameterValue.trim();
			}
			packageParams.put(parameter, v);
		}
 
		StringBuffer sb = new StringBuffer();
		Set es = packageParams.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 (!"sign".equals(k) && null != v && !"".equals(v)) {
				sb.append(k + "=" + v + "&");
			}
		}
		sb.append("key=" + API_KEY);
		// 將API返回的資料根據用簽名演算法進行計算新的簽名，用來跟API返回的簽名進行比較
 
		// 算出簽名
		String resultSign = "";
		String tobesign = sb.toString();
		if (null == charset || "".equals(charset)) {
			resultSign = MD5Utils.MD5Encode(tobesign, charset)
					.toUpperCase();
		} else {
			resultSign = MD5Utils.MD5Encode(tobesign, charset)
					.toUpperCase();
		}
		String tenpaySign = ((String) packageParams.get("sign")).toUpperCase();
		return tenpaySign.equals(resultSign);
	}
 
	// 請求方法
	public static String httpsRequest(String requestUrl, String requestMethod,
			String outputStr) {
		try {
 
			URL url = new URL(requestUrl);
			HttpURLConnection conn = (HttpURLConnection) url.openConnection();
 
			conn.setDoOutput(true);
			conn.setDoInput(true);
			conn.setUseCaches(false);
			// 設定請求方式（GET/POST）
			conn.setRequestMethod(requestMethod);
			conn.setRequestProperty("content-type",
					"application/x-www-form-urlencoded");
			// 當outputStr不為null時向輸出流寫資料
			if (null != outputStr) {
				OutputStream outputStream = conn.getOutputStream();
				// 注意編碼格式
				outputStream.write(outputStr.getBytes("UTF-8"));
				outputStream.close();
			}
			// 從輸入流讀取返回內容
			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);
			}
			// 釋放資源
			bufferedReader.close();
			inputStreamReader.close();
			inputStream.close();
			inputStream = null;
			conn.disconnect();
			return buffer.toString();
		} catch (ConnectException ce) {
			System.out.println("連線超時：{}" + ce);
		} catch (Exception e) {
			System.out.println("https請求異常：{}" + e);
		}
		return null;
	}
 
	// 退款的請求方法
	public static String httpsRequest2(String requestUrl, String requestMethod,
			String outputStr) throws Exception {
		KeyStore keyStore = KeyStore.getInstance("PKCS12");
		StringBuilder res = new StringBuilder("");
		FileInputStream instream = new FileInputStream(new File(
				"/home/apiclient_cert.p12"));
		try {
			keyStore.load(instream, "".toCharArray());
		} finally {
			instream.close();
		}
 
		// Trust own CA and all self-signed certs
		SSLContext sslcontext = SSLContexts.custom()
				.loadKeyMaterial(keyStore, "1313329201".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 httpost = new HttpPost(
					"https://api.mch.weixin.qq.com/secapi/pay/refund");
			httpost.addHeader("Connection", "keep-alive");
			httpost.addHeader("Accept", "*/*");
			httpost.addHeader("Content-Type",
					"application/x-www-form-urlencoded; charset=UTF-8");
			httpost.addHeader("Host", "api.mch.weixin.qq.com");
			httpost.addHeader("X-Requested-With", "XMLHttpRequest");
			httpost.addHeader("Cache-Control", "max-age=0");
			httpost.addHeader("User-Agent",
					"Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.0) ");
			StringEntity entity2 = new StringEntity(outputStr, Consts.UTF_8);
			httpost.setEntity(entity2);
			System.out.println("executing request" + httpost.getRequestLine());
 
			CloseableHttpResponse response = httpclient.execute(httpost);
 
			try {
				HttpEntity entity = response.getEntity();
 
				System.out.println("----------------------------------------");
				System.out.println(response.getStatusLine());
				if (entity != null) {
					System.out.println("Response content length: "
							+ entity.getContentLength());
					BufferedReader bufferedReader = new BufferedReader(
							new InputStreamReader(entity.getContent()));
					String text = "";
					res.append(text);
					while ((text = bufferedReader.readLine()) != null) {
						res.append(text);
						System.out.println(text);
					}
 
				}
				EntityUtils.consume(entity);
			} finally {
				response.close();
			}
		} finally {
			httpclient.close();
		}
		return res.toString();
 
	}
 
	// xml解析
	public static Map doXMLParse(String strxml) throws JDOMException,
			IOException {
		strxml = strxml.replaceFirst("encoding=\".*\"", "encoding=\"UTF-8\"");
 
		if (null == strxml || "".equals(strxml)) {
			return null;
		}
 
		Map m = new HashMap();
 
		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);
		}
 
		// 關閉流
		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();
	}
 
        public static String setXML(String return_code, String return_msg) {
		return "<xml><return_code><![CDATA[" + return_code
				+ "]]></return_code><return_msg><![CDATA[" + return_msg
				+ "]]></return_msg></xml>";
 
	}
}

5.3業務類

這裡我就只貼出Service層程式碼，其餘程式碼都類似，引數這裡只需要兩個，一個是微信訂單號，還有一個是訂單金額與退款金額，我們這裡兩個金額是一致的，注意一下這裡的退款金額單位是分，而支付寶是元。當然這裡也可以新增對應的業務邏輯，我們這裡不需要。

private boolean refundWeChat(String transactionId, Long orderAmount)
			throws RuntimeException {
		TreeMap<String, Object> parameters = new TreeMap<String, Object>();
		parameters.put("appid", WeChatConfig.APP_ID);
		parameters.put("mch_id", WeChatConfig.MCH_ID);
		parameters.put("nonce_str", CommonUtil.getRandomString(32));
		parameters.put("transaction_id", transactionId);
		parameters.put("out_refund_no", CommonUtil.getRandomString(32));
		parameters.put("total_fee", orderAmount);
		parameters.put("refund_fee", orderAmount);
                parameters.put("notify_url", WeChatConfig.REFUND_NOTIFY_URL);
		String sign = CommonUtil.createSign("UTF-8", parameters);
		parameters.put("sign", sign);

		String resContent = "";
		String tosend = CommonUtil.getRequestXml(parameters);
		try {
			resContent = CommonUtil.httpsRequest2(WeChatConfig.REFUND_URL, "POST", tosend);
			Map<String, String> map = CommonUtil.doXMLParse(resContent);
			if (map.get("return_code").toString().equalsIgnoreCase("SUCCESS")) {
				if (map.get("result_code").toString().equalsIgnoreCase("SUCCESS")) {
                                //此處可以新增退款成功業務邏輯
					return true;
				} else {
                                //此處可以新增退款失敗業務邏輯
					return false;
				}
			} else {
				return false;
			}
		} catch (Exception e) {
			e.printStackTrace();
			return false;
		}
	}

微信支付的申請退款就講到這裡，下一章講述微信退款結果通知介面開發。