java监听微信消息

要监听微信消息，您需要使用微信开放平台提供的API接口。首先，您需要在微信开放平台注册并创建应用程序。然后，您可以使用Java编写代码来访问API接口，以便获取和处理微信消息。

以下是一个简单的示例，用于从微信服务器接收消息并处理它们：

1. 创建一个Servlet来处理微信服务器的请求：

@WebServlet("/wechat")
public class WechatServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    private static final String TOKEN = "your_token";

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String signature = request.getParameter("signature");
        String timestamp = request.getParameter("timestamp");
        String nonce = request.getParameter("nonce");
        String echostr = request.getParameter("echostr");

        if (checkSignature(signature, timestamp, nonce)) {
            response.getWriter().print(echostr);
        } else {
            response.getWriter().print("invalid signature");
        }
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        ServletInputStream inputStream = request.getInputStream();
        String xml = IOUtils.toString(inputStream);

        // Parse the received XML message
        Map<String, String> message = MessageUtil.parseXml(xml);

        // Process the received message
        String responseXml = MessageUtil.processMessage(message);

        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/xml");
        response.getWriter().print(responseXml);
    }

    private boolean checkSignature(String signature, String timestamp, String nonce) {
        List<String> params = new ArrayList<String>();
        params.add(TOKEN);
        params.add(timestamp);
        params.add(nonce);
        Collections.sort(params);

        String str = "";
        for (String param : params) {
            str += param;
        }

        String encrypted = DigestUtils.sha1Hex(str);

        return encrypted.equals(signature);
    }
}

2. 创建一个工具类来帮助解析和处理接收到的消息：

public class MessageUtil {
    public static Map<String, String> parseXml(String xml) throws Exception {
        Map<String, String> map = new HashMap<String, String>();

        Document document = DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(new InputSource(new StringReader(xml)));

        Element root = document.getDocumentElement();
        NodeList nodeList = root.getChildNodes();

        for (int i = 0; i < nodeList.getLength(); i++) {
            Node node = nodeList.item(i);
            if (node instanceof Element) {
                Element element = (Element) node;
                map.put(element.getNodeName(), element.getTextContent());
            }
        }

        return map;
    }

    public static String processMessage(Map<String, String> message) {
        String fromUserName = message.get("FromUserName");
        String toUserName = message.get("ToUserName");
        String msgType = message.get("MsgType");
        String content = message.get("Content");

        String responseXml = "";

        if (msgType.equals("text")) {
            // Process text messages
            String responseContent = "您发送的是文本消息：" + content;
            responseXml = buildTextMessage(fromUserName, toUserName, responseContent);
        } else if (msgType.equals("image")) {
            // Process image messages
        } else if (msgType.equals("voice")) {
            // Process voice messages
        } else if (msgType.equals("video")) {
            // Process video messages
        } else if (msgType.equals("location")) {
            // Process location messages
        } else if (msgType.equals("link")) {
            // Process link messages
        } else if (msgType.equals("event")) {
            // Process event messages
        }

        return responseXml;
    }

    private static String buildTextMessage(String fromUserName, String toUserName, String content) {
        String responseXml = "<xml>";
        responseXml += "<ToUserName><![CDATA[" + fromUserName + "]]></ToUserName>";
        responseXml += "<FromUserName><![CDATA[" + toUserName + "]]></FromUserName>";
        responseXml += "<CreateTime>" + System.currentTimeMillis() / 1000 + "</CreateTime>";
        responseXml += "<MsgType><![CDATA[text]]></MsgType>";
        responseXml += "<Content><![CDATA[" + content + "]]></Content>";
        responseXml += "</xml>";

        return responseXml;
    }
}

3. 在您的应用程序中，您需要使用Java HTTP客户端来向微信服务器发送请求并接收响应。例如，您可以使用Apache HttpClient，如下所示：

HttpClient client = new DefaultHttpClient();
HttpPost post = new HttpPost("https://api.weixin.qq.com/cgi-bin/message/custom/send?access_token=ACCESS_TOKEN");
StringEntity entity = new StringEntity("your_message", "UTF-8");
post.setEntity(entity);
HttpResponse response = client.execute(post);
String responseJson = EntityUtils.toString(response.getEntity(), "UTF-8");

4. 最后，您需要将应用程序部署到一个Web服务器上，以便可以通过URL访问它。例如，您可以使用Tomcat或Jetty作为您的Web服务器。

请注意，以上代码仅用于示例目的，您需要根据您自己的需求进行修改和调整。同时，微信开放平台的API接口可能会随时更改，请确保您使用的是最新的API文档。