应用场景：
支付完成后，微信会把相关支付结果和用户信息发送给商户，商户需要接收处理，并返回应答。
对后台通知交互时，如果微信收到商户的应答不是成功或超时，微信认为通知失败，微信会通过一定的策略定期重新发起通知，尽可能提高通知的成功率，但微信不保证通知最终能成功。 （通知频率为15/15/30/180/1800/1800/1800/1800/3600，单位：秒）
注意：同样的通知可能会多次发送给商户系统。商户系统必须能够正确处理重复的通知。
推荐的做法是，当收到通知进行处理时，首先检查对应业务数据的状态，判断该通知是否已经处理过，如果没有处理过再进行处理，如果处理过直接返回结果成功。在对业务数据进行状态检查和处理之前，要采用数据锁进行并发控制，以避免函数重入造成的数据混乱。
特别提醒：商户系统对于支付结果通知的内容一定要做签名验证，防止数据泄漏导致出现“假通知”，造成资金损失。
//支付结果通知接口
@RequestMapping(“/qlydweixinotify.do”)
public void weixinotify(HttpServletRequest request,
HttpServletResponse response) {
PrintWriter out = null;
StringBuffer xmlStr = new StringBuffer();
try {
BufferedReader reader = request.getReader();
String line = null;
while ((line = reader.readLine()) != null) {
xmlStr.append(line);
}
Logger.getLogger(getClass()).debug(“支付回调通知：”+xmlStr.toString());
//检查xml是否有效
boolean flag=Signature.checkIsSignValidFromResponseString(xmlStr.toString());
WeixinNotifyResult result=null;
if(flag){
NotifyResData wxData=(NotifyResData) Util.getObjectFromXML(xmlStr.toString(),NotifyResData.class);
if(wxData !=null){
if(“SUCCESS”.equals(wxData.getReturn_code())){
OrderPayInfo orderPayInfo = new OrderPayInfo();
orderPayInfo.setOrderNum(wxData.getOut_trade_no());
orderPayInfo.setPayNum(wxData.getTransaction_id());
orderPayInfo.setPayPrice((double)wxData.getTotal_fee()/100+”“);
orderPayInfo.setPaySource(wxData.getOpenid());
orderPayInfo.setPayTime(wxData.getTime_end());
orderPayInfo.setPayType(“2”);//1支付宝，2微信支付
OrderMessage returnMessage = orderProductServer
.completeProductOrder(orderPayInfo);
if (OrderStatus.FAIL.equals(returnMessage
.getOrderStatus())) {
Logger.getLogger(getClass()).error(“远程接口完成订单失败”);
result=new WeixinNotifyResult(“FAIL”);
result.setReturn_msg(“远程接口完成订单失败”);
} else {
result=new WeixinNotifyResult(“SUCCESS”);
result.setReturn_msg(“成功”);
}
}else{
result=new WeixinNotifyResult(“FAIL”);
result.setReturn_msg(“失败”);
}
}else{
result=new WeixinNotifyResult(“FAIL”);
result.setReturn_msg(“解析参数格式失败”);
}
}else{
result=new WeixinNotifyResult(“FAIL”);
result.setReturn_msg(“签名失败”);
}
response.getWriter().write(result.toString());
} catch (Exception e) {
Logger.getLogger(getClass()).error(“qlydweixinotify.do”, e);
ResponeDeal.getInstance().sendResponseStr(response, “404”, “连接超时”);
} finally {
if (out != null) {
out.close();
}
}
}

模拟http请求工具类：
HttpsRequestUtil.java
package com.qlwb.weixin.util;

import java.io.IOException;

import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.HttpException;
import org.apache.commons.httpclient.methods.PostMethod;
import org.apache.commons.httpclient.methods.RequestEntity;
import org.apache.commons.httpclient.methods.StringRequestEntity;
import org.apache.log4j.Logger;

import com.qlwb.weixin.common.Configure;
import com.qlwb.weixin.common.Util;
import com.qlwb.weixin.protocol.pay_protocol.WxPayReqData;
import com.qlwb.weixin.protocol.payquery_protocol.PayQueryReqData;

public class HttpsRequestUtil {

/**
 * 
 * @方法名称:sendWxPayRequest
 * @内容摘要: ＜发送统一下单请求＞
 * @param body
 * @param outTradeNo
 * @param totalFee
 * @param spBillCreateIP
 * @return 
 * String
 * @exception 
 * @author:鹿伟伟
 * @创建日期:2016年2月19日-下午2:24:05
 */
public String sendWxPayRequest(String body,String detail,String outTradeNo,int totalFee,String spBillCreateIP
        )

{
    // 构造HTTP请求
    HttpClient httpclient = new HttpClient();

    PostMethod postMethod = new PostMethod(Configure.PAY_API);

    WxPayReqData wxdata = new WxPayReqData(body,detail,outTradeNo,totalFee,spBillCreateIP);

    String requestStr="";
    requestStr=Util.ConvertObj2Xml(wxdata);
    // 发送请求
    String strResponse = null;
    try {
        RequestEntity entity = new StringRequestEntity(
                requestStr.toString(), "text/xml", "UTF-8");
        postMethod.setRequestEntity(entity);
        httpclient.executeMethod(postMethod);
        strResponse = new String(postMethod.getResponseBody(), "utf-8");
        Logger.getLogger(getClass()).debug(strResponse);
    } catch (HttpException e) {
        Logger.getLogger(getClass()).error("sendWxPayRequest", e);
    } catch (IOException e) {
        Logger.getLogger(getClass()).error("sendWxPayRequest", e);
    } finally {
        postMethod.releaseConnection();
    }
    return strResponse;
}
/**
 * 
 * @方法名称:orderQueryRequest
 * @内容摘要: ＜查询订单信息＞
 * @param transaction_id 微信的订单号，优先使用
 * @return 
 * String
 * @exception 
 * @author:鹿伟伟
 * @创建日期:2016年2月19日-下午2:44:11
 */
public String orderQueryRequest(String transactionID, String outTradeNo
        )

{
    // 构造HTTP请求
    HttpClient httpclient = new HttpClient();

    PostMethod postMethod = new PostMethod(Configure.PAY_QUERY_API);

    PayQueryReqData wxdata = new PayQueryReqData(transactionID,outTradeNo);

    String requestStr="";
    requestStr=Util.ConvertObj2Xml(wxdata);
    // 发送请求
    String strResponse = null;
    try {
        RequestEntity entity = new StringRequestEntity(
                requestStr.toString(), "text/xml", "UTF-8");
        postMethod.setRequestEntity(entity);
        httpclient.executeMethod(postMethod);
        strResponse = new String(postMethod.getResponseBody(), "utf-8");

    } catch (HttpException e) {
        Logger.getLogger(getClass()).error("orderQueryRequest", e);
    } catch (IOException e) {
        Logger.getLogger(getClass()).error("orderQueryRequest", e);
    } finally {
        postMethod.releaseConnection();
    }
    return strResponse;
}

}