第一步：准备工作：准备小程序的APPID和SECRET
可登陆微信公众平台查看APPID和secret
第二部：获取token
微信提供了获取token的接口，访问此接口同时传入APPID和secret作为参数，就能获取token值。
接口地址为：tokenURL = https://api.weixin.qq.com/cgi-bin/token？grant_type=client_credential&appid=APPID&secret=SECRET
Java代码：
1 public static String getAccessToken() throws UnsupportedEncodingException, IOException{ 2 String tokenURL = https://api.weixin.qq.com/cgi-bin/token？grant_type=client_credential&appid=APPID&secret=SECRET 3 JSONObject jsonObject = null; 4 URL conn_url = new URL(tokenURL ); 5 HttpURLConnection conn = (HttpsURLConnection)conn_url.openConnection(); 6 conn.setRequestMethod("GET"); 7 conn.setReadTimeout(5000); 8 conn.setConnectTimeout(5000); 9 conn.connect(); 10 //output获取access_token是不会用到 11 12 //正常返回代码为200 13 if(conn.getResponseCode()==200){ 14 InputStream stream = conn.getInputStream(); 15 InputStreamReader inputStreamReader = new InputStreamReader(stream, "utf-8"); 16 BufferedReader bufferedReader = new BufferedReader(inputStreamReader); 17 String str = null; 18 StringBuffer buffer = new StringBuffer(); 19 while ((str = bufferedReader.readLine()) != null) { 20 buffer.append(str); 21 } 22 bufferedReader.close(); 23 inputStreamReader.close(); 24 stream.close(); 25 conn.disconnect(); 26 jsonObject = JSONObject.fromObject(buffer.toString()); 27 } 28 29 String access_token = jsonObject.getString("access_token"); 30 return access_token; 31 }
第三部：获取参数图片
微信官方提供了获取微信小程序二维码的接口，访问此接口，同时把第二步获取的token值作为参数传入，同时还需传入二维码内需要带的参数，和图片的一些设置参数，便可获取二维码图片的输入流。
接口地址：
https://api.weixin.qq.com/wxa/getwxacodeunlimit?access_token=access_token
基本的设置参数：
"scene", param --二维码内需要带的参数param
"path", "pages/ShouYe/ShouYe/ShouYe" --设置扫面二维码进入的页面
"width", width --设置二维码图片的大小 如果不设置，默认大小是430
"is_hyaline", true
"auto_color", true
生成二维码代码：
1 public static String getQRImg(String param,String size, HttpServletRequest request) { 2 3 4 String p=request.getSession().getServletContext().getRealPath("/"); 5 String codeUrl = p+"image/codeImg/"+System.currentTimeMillis()+param + "Code.png"; 6 String twoCodeUrl="/image/codeImg/"+System.currentTimeMillis()+param + "Code.png"; 7 try 8 { 9 String access_token = token; 10 URL url = new URL("https://api.weixin.qq.com/wxa/getwxacodeunlimit?access_token="+access_token); 11 HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection(); 12 httpURLConnection.setRequestMethod("POST");// 提交模式 13 // conn.setConnectTimeout(10000);//连接超时 单位毫秒 14 // conn.setReadTimeout(2000);//读取超时 单位毫秒 15 // 发送POST请求必须设置如下两行 16 httpURLConnection.setDoOutput(true); 17 httpURLConnection.setDoInput(true); 18 // 获取URLConnection对象对应的输出流 19 PrintWriter printWriter = new PrintWriter(httpURLConnection.getOutputStream()); 20 // 发送请求参数 21 JSONObject paramJson = new JSONObject(); 22 String width; 23 if(size !=null && !size.trim().equals("")){ 24 if(size.trim().matches("^[1-9][0-9]*$")){ 25 width = size.trim(); 26 }else 27 { 28 width = "430"; 29 } 30 }else{ 31 width = "430"; 32 } 33 paramJson.put("scene", param); 34 paramJson.put("path", "pages/ShouYe/ShouYe/ShouYe"); 35 paramJson.put("width", width); 36 paramJson.put("is_hyaline", true); 37 paramJson.put("auto_color", true); 38 /** 39 * line_color生效 40 * paramJson.put("auto_color", false); 41 * JSONObject lineColor = new JSONObject(); 42 * lineColor.put("r", 0); 43 * lineColor.put("g", 0); 44 * lineColor.put("b", 0); 45 * paramJson.put("line_color", lineColor); 46 * */ 47 48 printWriter.write(paramJson.toString()); 49 // flush输出流的缓冲 50 printWriter.flush(); 51 //开始获取数据 52 BufferedInputStream bis = new BufferedInputStream(httpURLConnection.getInputStream()); 53 OutputStream os = new FileOutputStream(new File(codeUrl)); 54 int len; 55 byte[] arr = new byte[1024]; 56 while ((len = bis.read(arr)) != -1) 57 { 58 os.write(arr, 0, len); 59 os.flush(); 60 } 61 os.close(); 62 } 63 catch (Exception e) 64 { 65 e.printStackTrace(); 66 } 67 return twoCodeUrl; 68 }