接入微信公众平台开发之用户关注（取消）事件触发后台自定义消息体通知给用户的实现过程

1.需求：用户关注公众号后回复给用户一个字符串，字符串不能重复使用即如果a用户关注公众号后商户后台回复给用户字符串str1后，b用户关注就是其他字符串，且a用户取消关注再次关注不回复消息体

2.实现过程：

　　①首先配置服务器url并开启，再次过程中需要微信后台与商户后台进行通信，所以，微信后台会发送请求，商户平台自定义接口回复相关内容即可完成通信。

　　　　②原理图：

　　③代码实现：

　　　　a.pcodecontroller:定义的一个接口类，用来处理微信服务器发送的请求

package com.java.zxf.controller;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.servlet.ServletInputStream;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.log4j.Logger;
import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import weixin.popular.bean.xmlmessage.XMLMessage;
import weixin.popular.bean.xmlmessage.XMLTextMessage;
import weixin.popular.support.ExpireKey;
import weixin.popular.support.expirekey.DefaultExpireKey;
import com.easytouch.util.MyCheck;
import com.java.zxf.dao.Pcodedao;
import com.java.zxf.domain.pcode;

@Controller
public class PcodeController {

    @Autowired
    private Pcodedao pcodedao;
    private Logger log = Logger.getLogger(getClass());
    
    @RequestMapping("/getbyid")
    @ResponseBody
    public Map<String, Object> getbyid(HttpServletRequest request,int id){
        pcode code = pcodedao.getcodebyid(id);
        Map<String, Object> map = new HashMap<String, Object>();
        map.put("code", code);
        return map;
    }
    
    //重复通知过滤
    private static ExpireKey expireKey = new DefaultExpireKey();


    //微信推送事件 url
    @RequestMapping("/openwx/getticket")
    public void getTicket(HttpServletRequest request, HttpServletResponse response)
            throws Exception {
        ServletInputStream inputStream = request.getInputStream();
        ServletOutputStream outputStream = response.getOutputStream(); String signature = request.getParameter("signature");
        String timestamp = request.getParameter("timestamp");
        String nonce = request.getParameter("nonce");
        String echostr = request.getParameter("echostr");

        //首次请求申请验证,返回echostr
        if(echostr!=null){
            outputStreamWrite(outputStream,echostr);
            return;
        }

        //验证请求签名
        if(!MyCheck.checkSignature(signature, timestamp, nonce)){
            System.out.println("The request signature is invalid");
            return;
        }

        boolean isreturn= false;
        //loger.info("1.收到微信服务器消息");
        Map<String, String> wxdata=parseXml(request);
        if(wxdata.get("MsgType")!=null){
            if("event".equals(wxdata.get("MsgType"))){
                //loger.info("2.1解析消息内容为：事件推送");
                if( "subscribe".equals(wxdata.get("Event"))){
                    //loger.info("2.2用户第一次关注 返回true哦");
                    isreturn=true;
                }
            }
        }

        if(isreturn == true){
            String openid = wxdata.get("FromUserName");
            String tosend = "抱歉,提货码已用完";
            String key = wxdata.get("FromUserName")+ "__"
                    + wxdata.get("ToUserName")+ "__"
                    + wxdata.get("MsgId") + "__"
                    + wxdata.get("CreateTime");
            if(expireKey.exists(key)){
                //重复通知不作处理
                //loger.info("3.1  重复通知了");
                return;
            }else{
                //loger.info("3.1  第一次通知");
                 //转换XML
                //loger.info("3.0 进入回复 转换对象："+key);
                pcode temp = pcodedao.getbyopenid(openid);
                if (temp==null){
                    List<pcode> pcodelist = pcodedao.getAllcode();
                    try{
                        pcode code = pcodelist.get(0);
                        tosend = "您的提货码为:"+code.getPickupcode();
                        int flag = pcodedao.update(code.getId(),openid);
                        if(flag==1){
                            System.out.println("更新成功,取货码已使用");
                        }else{
                            log.error("更新用户openid失败，取货码未能使用");
                        }
                    }catch(Exception e){
                        System.out.println("取货码已经用完");
                        log.info("取货码已经用完");
                    }
                  //loger.info("3.2  回复你好");
                    //创建回复
                    XMLMessage xmlTextMessage = new XMLTextMessage(
                            wxdata.get("FromUserName"),
                            wxdata.get("ToUserName"),
                            tosend);
                    expireKey.add(key);
                    //回复
                    xmlTextMessage.outputStreamWrite(outputStream);
                    return;
                }
                }
        }
        //loger.info("3.2  回复空");
        outputStreamWrite(outputStream,"");
    }

    /**
     * 数据流输出
     * @param outputStream
     * @param text
     * @return
     */
    private boolean outputStreamWrite(OutputStream outputStream, String text){
        try {
            outputStream.write(text.getBytes("utf-8"));
        } catch (UnsupportedEncodingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return false;
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return false;
        }
        return true;
    }

    /**
     * dom4j 解析 xml 转换为 map
     * @param request
     * @return
     * @throws Exception
     */
    public static Map<String, String> parseXml(HttpServletRequest request) throws Exception {
        // 将解析结果存储在HashMap中
        Map<String, String> map = new HashMap<String, String>();
        // 从request中取得输入流
        InputStream inputStream = request.getInputStream();
        // 读取输入流
        SAXReader reader = new SAXReader();
        Document document = reader.read(inputStream);
        // 得到xml根元素
        Element root = document.getRootElement();
        // 得到根元素的所有子节点
        List<Element> elementList = root.elements();

        // 遍历所有子节点
        for (Element e : elementList)
            map.put(e.getName(), e.getText());

        // 释放资源
        inputStream.close();
        inputStream = null;
        return map;
    }

    /**
     * 回复微信服务器"文本消息"
     * @param response
     * @param returnvaleue
     */
    public void output(HttpServletResponse response, String returnvaleue) {
        try {
            PrintWriter pw = response.getWriter();
            pw.write(returnvaleue);
            pw.flush();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

　　　　b.pcodedao:商户后台应用-数据层；定义的读写数据的类

package com.java.zxf.dao;

import java.util.List;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;
import org.springframework.stereotype.Repository;

import com.java.zxf.domain.pcode;
@Repository
public interface Pcodedao {
    @Select("select * from pcode where id=#{id}")
    public pcode getcodebyid(int id);
    
    @Select("select * from pcode where openid is null or openid=''")
    public List<pcode> getAllcode();
    
    @Select("select * from pcode where openid=#{openid}")
    public pcode getbyopenid(String openid);
    
    @Update("update pcode set openid=#{openid} where id=#{id}")
    public int update(@Param(value="id")int id,@Param(value="openid")String openid);
}

　　　　c.pom.xml中添加的依赖包

		<dependency>
		    <groupId>dom4j</groupId>
		    <artifactId>dom4j</artifactId>
		    <version>1.6.1</version>
		</dependency>
		<dependency>
		  <groupId>com.github.liyiorg</groupId>
		  <artifactId>weixin-popular</artifactId>
		  <version>2.8.24</version>
		</dependency>

　　三.总结：微信公众平台提供了包括关注动作，被动回复消息在内的一系列动作，具体见如下链接：：https://mp.weixin.qq.com/wiki?t=resource/res_main&id=mp1421140454