微信掃一掃功能調用

1. 第一步：

   設置調用微信js安全域名，就可以在該域名下調用微信的js接口
   

2. 第二步：將下面的js附在需要調用微信掃一掃的頁面上，前提是需要引入微信的js[]

3. 第三步： 參考官方文檔 https://mp.weixin.qq.com/wiki?t=resource/res_main&id=mp1421141115&token=876521668&lang=zh_CN

   通過後臺獲取js權限簽名jsapi_ticket【參考文檔：http://mp.weixin.qq.com/wiki/7/aaa137b55fb2e0456bf8dd9148dd613f.html#.E9.99.84.E5.BD.951-JS-SDK.E4.BD.BF.E7.94.A8.E6.9D.83.E9.99.90.E7.AD.BE.E5.90.8D.E7.AE.97.E6.B3.95】

後臺獲取簽名代碼：

package com.epoch.wap.common;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Formatter;
import java.util.HashMap;
import java.util.Map;
import java.util.UUID;

import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

import com.epoch.common.utils.JsonUtil;

/** 
 * 官方給的使用js的驗證工具 
 * @author Administrator 
 * 
 */  
public class JsSignUtil {  
    public static String accessToken = null;  
    public static Map<String, Object> sign(String url) {   

        String sendUrl = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=**appid**&secret= **secret**";
        String result = getHttpResult(sendUrl);
        Object accessResult = JsonUtil.getValueFromJson(result, "access_token");
        String signUrl = "https://api.weixin.qq.com/cgi-bin/ticket/getticket?access_token="+accessResult.toString()+"&type=jsapi";
        String resultSign = getHttpResult(signUrl);
        Object ticket = JsonUtil.getValueFromJson(resultSign, "ticket");
        Map<String, Object> ret = new HashMap<String, Object>();  
        String nonce_str = create_nonce_str();  
        String timestamp = create_timestamp();  
        String string1;  
        String signature = "";  

        //注意這裏參數名必須全部小寫，且必須有序  
        string1 = "jsapi_ticket=" + ticket +
                  "&noncestr=" + nonce_str +  
                  "&timestamp=" + timestamp +  
                  "&url=" + url;  
        try  
        {  
            MessageDigest crypt = MessageDigest.getInstance("SHA-1");  
            crypt.reset();  
            crypt.update(string1.getBytes("UTF-8"));  
            signature = byteToHex(crypt.digest());  
        }  
        catch (NoSuchAlgorithmException e)  
        {  
            e.printStackTrace();  
        }  
        catch (UnsupportedEncodingException e)  
        {  
            e.printStackTrace();  
        }  

        ret.put("url", url); 
        ret.put("nonceStr", nonce_str);  
        ret.put("timestamp", timestamp);  
        ret.put("signature", signature); 
        ret.put("jsapi_ticket", ticket); 
        ret.put("appId", "wx154f74654ae04891");
        return ret;  
    }  


    /** 
     * 隨機加密 
     * @param hash 
     * @return 
     */  
    private static String byteToHex(final byte[] hash) {  
        Formatter formatter = new Formatter();  
        for (byte b : hash)  
        {  
            formatter.format("%02x", b);  
        }  
        String result = formatter.toString();  
        formatter.close();  
        return result;  
    }  

    /*
     * 獲取訪問地址鏈接返回值
     */
    private static String getHttpResult(String url) {
        String result = "";
        HttpGet httpRequest = new HttpGet(url);
        try {
            HttpResponse httpResponse = HttpClients.createDefault().execute(httpRequest);
            if (httpResponse.getStatusLine().getStatusCode() == 200) {
                result = EntityUtils.toString(httpResponse.getEntity());
            }
        } catch (ClientProtocolException e) {
            e.printStackTrace();
            result = e.getMessage().toString();
        } catch (IOException e) {
            e.printStackTrace();
            result = e.getMessage().toString();
        }
        return result;
    }
    /** 
     * 產生隨機串--由程序自己隨機產生 
     * @return 
     */  
    private static String create_nonce_str() {  
        return UUID.randomUUID().toString();  
    }  


    /** 
     * 由程序自己獲取當前時間 
     * @return 
     */  
    private static String create_timestamp() {  
        return Long.toString(System.currentTimeMillis() / 1000);  
    }  
}  

官方文檔示例：

參考以下文檔獲取access_token（有效期7200秒，開發者必須在自己的服務全局緩存access_token）：../15/54ce45d8d30b6bf6758f68d2e95bc627.html
用第一步拿到的access_token 採用http GET方式請求獲得jsapi_ticket（有效期7200秒，開發者必須在自己的服務全局緩存jsapi_ticket）：https://api.weixin.qq.com/cgi-bin/ticket/getticket?access_token=ACCESS_TOKEN&type=jsapi

4 第四步： 前臺進入頁面：`

 @RequestMapping(value = "/tiaoma")
public String tiaoma( HttpServletRequest request,GoodsVO goods) throws Exception {

    String Url=request.getRequestURL()+"?"+request.getQueryString().toString();;
    Map<String, Object> resMap = new HashMap<String, Object>();
    resMap = JsSignUtil.sign(Url);
    request.setAttribute("nonceStr", resMap.get("nonceStr"));
    request.setAttribute("timestamp", resMap.get("timestamp"));
    request.setAttribute("signature", resMap.get("signature"));
    request.setAttribute("appId", resMap.get("appId"));
    request.setAttribute("url", resMap.get("url"));
    request.setAttribute("jsapi_ticket",                                  resMap.get("jsapi_ticket"));
    return "index/tiaoma";
}`