对柳峰博主的微信公众号后台示例的部分重构

柳峰博主的专栏（http://blog.csdn.net/column/details/wechatmp.html）和王信平博主的专栏（http://www.cnblogs.com/wangshuo1/）对微信公众号开发已经做了比较详尽的阐述，基本上照搬，就可以做出第一个微信公众号后台应用。但是在『照搬』的过程中，发现有些地方总是觉得别扭，由着完美主义者的性格使然，对以下这几个地方做个小优化吧。

一、区别消息和响应

原来的消息类（用户发给后台）和响应类（后台回给用户）有这些：

我改成了这样的：

我把『消息Message』和『响应Response』在命名上分开了。这样在编程时不会总是想着要去区别，这个『Message』究竟是用户发给后台的『消息』呢，还是后台回给用户的『响应』。

二、给消息和响应添加构造函数

原来消息和响应都只是使用缺省构造函数（详见http://blog.csdn.net/lyq8479/article/details/8949088），实际上是把这两个类当做了『结构体』来看待。基于面向对象的思想，还是觉得需要有构造函数。

2.1 BaseMessage类的构造函数

   public BaseMessage(String toUserName, String fromUserName, String createTime, String msgType, String msgId){
        this.ToUserName=toUserName;
        this.FromUserName=fromUserName;
        this.CreateTime=Long.parseLong(createTime);
        this.MsgType=msgType;
        this.MsgId=Long.parseLong(msgId);
    }

    public BaseMessage(Map<String, String> mapMessage){
        try {
            // 开发者微信号
            String toUserName = mapMessage.get("ToUserName");
            // 发送方帐号（open_id）
            String fromUserName = mapMessage.get("FromUserName");
            // 消息类型
            String msgType = mapMessage.get("MsgType");
            // 建立时间
            String createTime = mapMessage.get("CreateTime");
            // 消息ID
            String msgId = mapMessage.get("MsgId");

            this.ToUserName = toUserName;
            this.FromUserName = fromUserName;
            this.CreateTime = Long.parseLong(createTime);
            this.MsgType = msgType;
            this.MsgId = Long.parseLong(msgId);
        }
        catch (Exception e) {
            e.printStackTrace();
        }
    }

2.2 ImageMessage类的构造函数

    public ImageMessage(String toUserName,
                        String fromUserName,
                        String createTime,
                        String msgType,
                        String msgId,
                        String picUrl) {
        super(toUserName,fromUserName,createTime,msgType,msgId);
        assert (msgType.equals(MessageUtil.REQ_MESSAGE_TYPE_IMAGE));
        this.PicUrl=picUrl;
    }

    public ImageMessage(Map<String, String> mapMessage){
        super(mapMessage);
        assert (this.getMsgType().equals(MessageUtil.REQ_MESSAGE_TYPE_IMAGE));
        this.PicUrl=mapMessage.get("PicUrl");
    }

2.3 TextMessage类的构造函数

    public TextMessage(String toUserName,
                       String fromUserName,
                       String createTime,
                       String msgType,
                       String msgId,
                       String content) {
        super(toUserName,fromUserName,createTime,msgType,msgId);
        assert (msgType.equals(MessageUtil.REQ_MESSAGE_TYPE_TEXT));
        this.Content=content;

    }

    public TextMessage(Map<String, String> mapMessage){
        super(mapMessage);
        assert (this.getMsgType().equals(MessageUtil.REQ_MESSAGE_TYPE_TEXT));
        this.Content=mapMessage.get("Content");
    }

这里只列举了消息类的基类、图片消息、文本消息三个构造函数，其余的位置消息、声音消息、短视频、视频、链接消息的构造函数类似。

2.4 BaseResponse类的构造函数（这个有点意思）

    public BaseResponse(BaseMessage baseMessage){
        this.ToUserName=baseMessage.getFromUserName(); //返回的目标是当初的发送源
        this.FromUserName=baseMessage.getToUserName(); //发送的来源是当初的发送目标
        this.MsgType= MessageUtil.RESP_MESSAGE_TYPE_TEXT; // 默认返回消息为文本
        this.CreateTime=new Date().getTime(); //默认为当前时间
        this.FuncFlag=0; //默认为非星标
    }

    public BaseResponse(String toUserName,String fromUserName, String msgType){
        this.ToUserName=toUserName;
        this.FromUserName=fromUserName;
        this.MsgType=msgType;
        this.CreateTime=new Date().getTime(); //默认为当前时间
        this.FuncFlag=0; //默认为非星标
    }

响应类的基类的构造函数，我使用了消息类的基类作为参数，是因为响应消息的返回目标，就是当初的发送源（用户），响应消息的发送源，其实就是当初的发送目标（微信后台程序）。

2.5 TextResponse类的构造函数

    public TextResponse(String toUserName,String fromUserName, String msgType,String content){
        super(toUserName,fromUserName,msgType);
        this.Content=content;
    }
    public TextResponse(BaseMessage baseMessage,
                         String content){
        super(baseMessage);
        this.setMsgType(MessageUtil.RESP_MESSAGE_TYPE_TEXT);
        this.Content=content;
    }

2.6 Article类的构造函数

    public Article(String title, String description, String picUrl, String url) {
        this.Title=title;
        this.Description=description;
        this.PicUrl=picUrl;
        this.Url=url;
    }

2.7 NewsResponse类的构造函数

public class NewsResponse extends BaseResponse {
    // 图文消息个数，限制为10条以内
    private int ArticleCount;
    // 多条图文消息信息，默认第一个item为大图
    private List<Article> Articles;

    public NewsResponse(String toUserName,String fromUserName, String msgType){
        super(toUserName,fromUserName,msgType);
        ArticleCount=0;
        this.Articles = new ArrayList<Article>();
    }
    public NewsResponse(BaseMessage baseMessage){
        super(baseMessage);
        this.setMsgType(MessageUtil.RESP_MESSAGE_TYPE_NEWS);
        ArticleCount=0;
        this.Articles = new ArrayList<Article>();
    }

    //如果已经达到10篇文章,图文消息不可以再增加新的文章。返回FALSE；
    public boolean addArticle(Article article) {
        if (ArticleCount>=10){
            return false;
        }
        Articles.add(article);
        ArticleCount++;
        return true;
    }
    public Article getArticle(int articleIndex){
        return Articles.get(articleIndex);
    }

    public int getArticleCount() {
        return ArticleCount;
    }

//    public void setArticleCount(int articleCount) {
//        ArticleCount = articleCount;
//    }

    public List<Article> getArticles() {
        return Articles;
    }

//    public void setArticles(List<Article> articles) {
//        Articles = articles;
//    }
}

这个NewsResponse类也要说一下，原来的设计也够奇葩的，居然直接把List结构暴露出来对其读写，List里的Article的数量，可以单独赋值，呵呵。于是果断注释掉计数变量的读写方法，新增了addArticle和getArticle这两个方法，用以从List中添加和获取Article，计算变量，应该自动累加，不应该对其手工赋值。

MusicResponse类的改造类似，不细说了。

三、归一化命名

原来的响应消息转成XML有三个函数，分别是textMessageToXml、musicMessageToXml、newsMessageToXml（详见http://blog.csdn.net/lyq8479/article/details/8949088），我把它们的命名归一为responseToXml，调用的时候，也不用区别传进去的是啥响应消息来选择不同名字的函数，省心。

    /**
     * 文本消息对象转换成xml
     *
     * @param textMessage 文本消息对象
     * @return xml
     */
    public static String responseToXml(TextResponse textMessage) {
        xstream.alias("xml", textMessage.getClass());
        return xstream.toXML(textMessage);
    }

    /**
     * 音乐消息对象转换成xml
     *
     * @param musicMessage 音乐消息对象
     * @return xml
     */
    public static String responseToXml(MusicResponse musicMessage) {
        xstream.alias("xml", musicMessage.getClass());
        return xstream.toXML(musicMessage);
    }

    /**
     * 图文消息对象转换成xml
     *
     * @param newsMessage 图文消息对象
     * @return xml
     */
    public static String responseToXml(NewsResponse newsMessage) {
        xstream.alias("xml", newsMessage.getClass());
        xstream.alias("item", newsMessage.getArticle(0).getClass());
        return xstream.toXML(newsMessage);
    }

四、构造消息路由

原来的消息处理的主函数（详见http://blog.csdn.net/lyq8479/article/details/9393195），在一个超级巨大的processRequest函数中对消息进行处理，一堆if else if 下来，眼都花了，所以我简化了processRequest函数，只在这个函数里面构造消息路由，针对不同类型的消息，转去不同的处理逻辑中。

   //定义一个logger,用于发送日志,可以在console或者服务器上看到。存储目录在log4j.properties中定义
    private static final Logger logger = Logger.getLogger(CoreService.class);

    //处理请求
    public static String processRequest(HttpServletRequest request){
        String returnMsg=null;
        try{
            Map<String, String> requestMap = MessageUtil.parseXml(request); //解析XML
            String msgType = requestMap.get("MsgType"); //消息类型
            logger.info("***step1 msgType=" + msgType);
            switch (msgType){
                case MessageUtil.REQ_MESSAGE_TYPE_TEXT:
                    returnMsg=HandleTextMsg(new TextMessage(requestMap));
                    break;
                case MessageUtil.REQ_MESSAGE_TYPE_IMAGE:
                    returnMsg=HandleImageMsg(new ImageMessage(requestMap));
                    break;
                case MessageUtil.REQ_MESSAGE_TYPE_LINK:
                    returnMsg=HandleLinkMsg(new LinkMessage(requestMap));
                    break;
                case MessageUtil.REQ_MESSAGE_TYPE_LOCATION:
                    returnMsg=HandleLocationMsg(new LocationMessage(requestMap));
                    break;
                case MessageUtil.REQ_MESSAGE_TYPE_SHORT_VIDEO:
                    returnMsg=HandleShortVideoMsg(new ShortVideoMessage(requestMap));
                    break;
                case MessageUtil.REQ_MESSAGE_TYPE_VIDEO:
                    returnMsg=HandleVideoMsg(new VideoMessage(requestMap));
                    break;
                case MessageUtil.REQ_MESSAGE_TYPE_VOICE:
                    returnMsg=HandleVoiceMsg(new VoiceMessage(requestMap));
                    break;
                case MessageUtil.REQ_MESSAGE_TYPE_EVENT:
                    // 事件类型
                    String eventType = requestMap.get("Event");
                    switch (eventType){
                        case MessageUtil.EVENT_TYPE_SUBSCRIBE:
                            returnMsg=HandleSubscribeEvent(new BaseMessage(requestMap));
                            break;
                        case MessageUtil.EVENT_TYPE_UNSUBSCRIBE:
                            returnMsg=HandleUnsubscribeEvent(new BaseMessage(requestMap));
                            break;
                        case MessageUtil.EVENT_TYPE_CLICK:
                            returnMsg=HandleClickEvent(new BaseMessage(requestMap));
                            break;
                        default:
                            returnMsg=HandleDefaultMsgOrEvent(new BaseMessage(requestMap));
                    }
                    break;
                default:
                    returnMsg=HandleDefaultMsgOrEvent(new BaseMessage(requestMap));
            }
        }catch (Exception e) {
            e.printStackTrace();
        }
        return returnMsg;
    }

下面是对各种消息的handle函数

    public static String HandleTextMsg(TextMessage textMessage)
    {
        String respContent = "您发送的是文本消息!";
        if (textMessage.getContent().indexOf("/:") > -1)
            respContent="你"+textMessage.getContent()+"什么?";
        TextResponse textResponse=new TextResponse(textMessage, respContent);
        String respMsg=MessageUtil.responseToXml(textResponse);
        logger.info("***step2 Response=" + respMsg);
        return respMsg;
    }
    public static String HandleImageMsg(ImageMessage imageMessage)
    {
        String title="鉴定结果";
        String picUrl=imageMessage.getPicUrl();
        String forwardUrl= HttpTools.imagePlusPlusPath+picUrl;
        logger.info("***step2 image++ Url=" + forwardUrl);

        //从image++网站识别上传的图片的拍摄地点、拍摄物体。
        String imagePlusPlusReturn=getHttpResponse(forwardUrl);
        logger.info("***step3 image++ Response=" + imagePlusPlusReturn);
        String description = ReadJSONString(imagePlusPlusReturn);
        logger.info("***step4 image++ Response=" + description);

        Article article=new Article(title,description,picUrl,forwardUrl);
        NewsResponse newsResponse=new NewsResponse(imageMessage);
        newsResponse.addArticle(article);
        String respMsg=MessageUtil.responseToXml(newsResponse);
        logger.info("***step5  Weixin Response=" + respMsg);
        return respMsg;
    }
    public static String HandleLinkMsg(LinkMessage linkMessage)
    {
        String respContent = "您发送的是链接!";
        TextResponse textResponse=new TextResponse(linkMessage, respContent);
        String respMsg=MessageUtil.responseToXml(textResponse);
        logger.info("***step2 Response=" + respMsg);
        return respMsg;
    }
    public static String HandleLocationMsg(LocationMessage locationMessage)
    {
        String respContent = "您发送的是地理位置!";
        TextResponse textResponse=new TextResponse(locationMessage, respContent);
        String respMsg=MessageUtil.responseToXml(textResponse);
        logger.info("***step2 Response=" + respMsg);
        return respMsg;
    }
    public static String HandleShortVideoMsg(ShortVideoMessage shortVideoMessage)
    {
        String respContent = "您发送的是小视频!";
        TextResponse textResponse=new TextResponse(shortVideoMessage, respContent);
        String respMsg=MessageUtil.responseToXml(textResponse);
        logger.info("***step2 Response=" + respMsg);
        return respMsg;
    }
    public static String HandleVideoMsg(VideoMessage videoMessage)
    {
        String respContent = "您发送的是视频!";
        TextResponse textResponse=new TextResponse(videoMessage, respContent);
        String respMsg=MessageUtil.responseToXml(textResponse);
        logger.info("***step2 Response=" + respMsg);
        return respMsg;
    }
    public static String HandleVoiceMsg(VoiceMessage voiceMessage)
    {
        String respContent = "您发送的是语音!";
        TextResponse textResponse=new TextResponse(voiceMessage, respContent);
        String respMsg=MessageUtil.responseToXml(textResponse);
        logger.info("***step2 Response=" + respMsg);
        return respMsg;
    }
    public static String HandleSubscribeEvent(BaseMessage baseMessage)
    {
        String respContent = "欢迎订阅！";
        TextResponse textResponse=new TextResponse(baseMessage, respContent);
        String respMsg=MessageUtil.responseToXml(textResponse);
        logger.info("***step2 Response=" + respMsg);
        return respMsg;
    }
    public static String HandleUnsubscribeEvent(BaseMessage baseMessage)
    {
        String respContent = "再见,希望您再来!";
        TextResponse textResponse=new TextResponse(baseMessage, respContent);
        String respMsg=MessageUtil.responseToXml(textResponse);
        logger.info("***step2 Response=" + respMsg);
        return respMsg;
    }
    public static String HandleClickEvent(BaseMessage baseMessage)
    {
        String respContent = "您点击了自定义菜单!";
        TextResponse textResponse=new TextResponse(baseMessage, respContent);
        String respMsg=MessageUtil.responseToXml(textResponse);
        logger.info("***step2 Response=" + respMsg);
        return respMsg;
    }
    public static String HandleDefaultMsgOrEvent(BaseMessage baseMessage)
    {
        String respContent = "请求不可识别，请稍候尝试！";
        TextResponse textResponse=new TextResponse(baseMessage, respContent);
        String respMsg=MessageUtil.responseToXml(textResponse);
        logger.info("***step2 Response=" + respMsg);
        return respMsg;
    }

五、应用：试试图像识别

我的第一个微信公众号后台应用，是识别用户上传的图片，是什么东西，在哪里拍摄的。调用的是image++网站的api，核心代码如下：

/*
读取一个网址的所有返回内容
 */
    public static String getHttpResponse(String connectUrl) {
        BufferedReader in = null;
        StringBuffer result = null;
        try {
            URI uri = new URI(connectUrl);
            URL url = uri.toURL();
            URLConnection connection = url.openConnection();
            connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
            connection.setRequestProperty("Charset", "utf-8");
            connection.connect();

            result = new StringBuffer();
            //读取URL的响应
            in = new BufferedReader(new InputStreamReader(
                    connection.getInputStream()));
            String line;
            while ((line = in.readLine()) != null) {
                result.append(line);
            }

            return result.toString();

        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            try {
                if (in != null) {
                    in.close();
                }
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }
        return null;
    }

    /*
    从JSON字符串中读取某些关键信息
    JSON文件来自:http://www.imageplusplus.com/doc
     */
    public static String ReadJSONString(String jSonString){
        try {
            int imageConfidenceIndex=jSonString.indexOf("confidence",jSonString.indexOf("image"));
            int imageConfidenceIndexEnd=jSonString.indexOf(",",imageConfidenceIndex);
            String imageConfidence=jSonString.substring(imageConfidenceIndex+12,imageConfidenceIndexEnd);
            int imageConfidencePercent=(int)(Float.parseFloat(imageConfidence)*100);
            int imageValueIndex=jSonString.indexOf("value",jSonString.indexOf("image"));
            int imageValueIndexEnd=jSonString.indexOf("}",imageValueIndex)-1;
            String imageValue=jSonString.substring(imageValueIndex+8,imageValueIndexEnd).trim();

            int sceneConfidenceIndex=jSonString.indexOf("confidence",jSonString.indexOf("scene"));
            int sceneConfidenceIndexEnd=jSonString.indexOf(",",sceneConfidenceIndex);
            String sceneConfidence=jSonString.substring(sceneConfidenceIndex+12,sceneConfidenceIndexEnd);
            int sceneConfidencePercent=(int)(Float.parseFloat(sceneConfidence)*100);
            int sceneValueIndex=jSonString.indexOf("value",jSonString.indexOf("scene"));
            int sceneValueIndexEnd=jSonString.indexOf("}",sceneValueIndex)-1;
            String sceneValue=jSonString.substring(sceneValueIndex+8,sceneValueIndexEnd).trim();

            String result="这张照片有【"+imageConfidencePercent+"%】的可能是【"+imageValue+"】," +
                    "有【"+sceneConfidencePercent+"%】的可能是在【"+sceneValue+"】拍摄的。";
            return result;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return "服务器秀逗了,请重试!";
    }
}

全部的源代码，我放在了这里：20161013微信公众号后台应用示例src.zip

示例源码中用到几个外部jar lib，去官网下载，然后扔进项目里面就好。