微信退款接口

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.security.KeyStore;
import java.util.ArrayList;
import java.util.Collections;
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.commons.codec.digest.DigestUtils;
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.conn.ssl.SSLContexts;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import org.dom4j.Document;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;

import com.llread.flow.common.Config;
import com.llread.flow.common.Constants;
import com.llread.flow.common.Dom4jUtil;
import com.llread.flow.common.Util;

public class Test {
	public static void main(String[] args) throws Exception{
		Map params = new HashMap();
		params.put("appid", Config.getParam(Constants.WX_APP_ID));
		params.put("mch_id", Config.getParam(Constants.WX_MCH_ID));
		params.put("nonce_str", Util.getRandomString(16));
		//单号
		params.put("out_trade_no", "danhaoceshi001");
		//退款单号
		params.put("out_refund_no", "danhaoceshi001");
		//订单金额
		params.put("total_fee", "1");
		//退款金额
		params.put("refund_fee", "1");
		//退款原因
		params.put("refund_desc", "Recharge failed");
		
		Document doc = DocumentHelper.createDocument();
		Element root = DocumentHelper.createElement("xml");
		doc.setRootElement(root);
		List keys = new ArrayList(params.keySet());
		Collections.sort(keys);
		StringBuilder str = new StringBuilder();
		for (String key : keys) {
			String value = params.get(key);
			if (key.equals("sign")) {
				Dom4jUtil.setElementCDATAText(root, "/" + key, value);
			} else {
				Dom4jUtil.setElementText(root, "/" + key, value);
			}
			str.append(key + "=" + value + "&");
		}
		str.append("key=" + Config.getParam(Constants.WX_MCH_SECRET));
		// 签名
		Dom4jUtil.setElementText(root, "/sign",DigestUtils.md5Hex(str.toString()).toUpperCase());
		System.out.println("请求参数:"+doc.asXML());
		
		KeyStore keyStore = KeyStore.getInstance("PKCS12");
		FileInputStream instream = new FileInputStream(new File("D:/apiclient_cert.p12"));// 放退款证书的路径
		try {
			keyStore.load(instream, Config.getParam(Constants.WX_MCH_ID).toCharArray());
		} finally {
			instream.close();
		}

		SSLContext sslcontext = SSLContexts.custom()
				.loadKeyMaterial(keyStore, Config.getParam(Constants.WX_MCH_ID).toCharArray()).build();
		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/secapi/pay/refund");// 退款接口

			System.out.println("executing request" + httpPost.getRequestLine());
			StringEntity reqEntity = new StringEntity(doc.asXML());
			// 设置类型
			reqEntity.setContentType("application/x-www-form-urlencoded");
			httpPost.setEntity(reqEntity);
			CloseableHttpResponse response = httpclient.execute(httpPost);
			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(), "UTF-8"));
					String text;
					StringBuffer sb = new StringBuffer();
					while ((text = bufferedReader.readLine()) != null) {
						//System.out.println("返回参数:"+text);
						sb.append(text);
					}
					System.out.println("返回参数:"+sb);
					doc = Dom4jUtil.parseXml(sb.toString());
					root = doc.getRootElement();
					String code = Dom4jUtil.getElementText(root, "return_code", "FAIL");
					//退款返回失败
					if (!code.equals("SUCCESS")) {
						System.out.println(Dom4jUtil.getElementText(root, "return_msg", "未知错误"));
					}
					code = Dom4jUtil.getElementText(root, "result_code", "FAIL");
					//退款失败原因
					if (!code.equals("SUCCESS")) {
						System.out.println(Dom4jUtil.getElementText(root, "err_code", "未知代码")
								+ ":"+ Dom4jUtil.getElementText(root, "err_code_des", "未知错误"));
					}
				}
				EntityUtils.consume(entity);
			} finally {
				response.close();
			}
		} finally {
			httpclient.close();
		}
	}

PS：

1.签名错误问题：如果在微信官网验证过签名且签名正确，但是在代码中依旧返回错误，看下你的参数是否包含中文

2.涉及到撤回和退款需要的证书： 微信商户平台-账户中心--API安全出下载