一、本节要点
1.获取临时素材接口
请求方式：GET（HTTPS）
请求地址：https://qyapi.weixin.qq.com/cgi-bin/media/get?access_token=ACCESS_TOKEN&media_id=MEDIA_ID
2.获取临时素材接口的返回结果
企业微信官方开发文档中说明的返回结果如下：
若你以为这就是返回结果，然后跟之前一样，先访问接口，从http连接的输入流中的获取回结果的文本内容，你会发现你接收到的结果是一堆乱码。
这是为何？
以图片为例，此处千万要注意，微信返回的结果是一个文件流形式的图片，当我们从http连接的输入流中的获取回结果的文本内容，也就是获取图片的文本内容时，当然就是一堆乱码了。
这就好比你用记事本打开一张图片，然后发现内容是一片乱码。这再正常不过。所以我们接受图片的时候不能只接收文本数据，而是要接收流。
千万得注意：获取临时素材时，微信返回的结果是一个流形式的临时素材。
我们需要做的就是调用接口，获取http连接的输入流中数据，再将输入流中的数据写入到输出流，再通过输出流生成一张图片。这张图片就是微信返回的临时素材了。
3.下载文件时的文件路径
request.getSession().getServletContext().getRealPath("").replaceAll("\\\\", "/")
将获取路径：%TOMCAT_HOME%/webapp/工程名。若不是这个路径就请参考：Eclipse中的Web项目自动部署到Tomcat
String savePath=request.getSession().getServletContext().getRealPath("").replaceAll("\\\\", "/")+"/img/";
将获取路径：%TOMCAT_HOME%/webapp/工程名/img/
即从微信服务器下载的图片都保存在这个路径下。
二、代码实现
这里承接上一节。在上一节中我们完成了JSSDK的配置，并且用图片上传接口将图片上传到了微信服务器。这一节我们需要做的就是在图片上传到微信服务器后，根据微信服务器返回的serverId(即mediaId)来调用获取临时素材的接口，进行临时素材的下载，并保存到本地指定的路径下。
2.1 UploadExpenseAccaoutServlet
package com.ray.servlet; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import com.ray.service.TempMaterialService; import com.ray.util.WeiXinParamesUtil; import com.ray.util.WeiXinUtil; /** * Servlet implementation class UploadExpenseAccaoutServlet */ @WebServlet("/UploadExpenseAccaoutServlet") public class UploadExpenseAccaoutServlet extends HttpServlet { private static final long serialVersionUID = 1L; /** * @see HttpServlet#HttpServlet() */ public UploadExpenseAccaoutServlet() { super(); // TODO Auto-generated constructor stub } /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub String mediaId=request.getParameter("serverId"); System.out.println("serverId:"+mediaId); String accessToken= WeiXinUtil.getAccessToken(WeiXinParamesUtil.corpId, WeiXinParamesUtil.contactsSecret).getToken(); System.out.println("accessToken:"+accessToken); //String savePath=System.getProperty("user.dir").replaceAll("\\\\", "/")+"/WebContent/img/"+mediaId+".png"; String savePath=request.getSession().getServletContext().getRealPath("").replaceAll("\\\\", "/")+"/img/"; System.out.println("savePath:"+savePath); //2.调用业务类，获取临时素材 TempMaterialService tms=new TempMaterialService(); tms.getTempMaterial(accessToken, mediaId,savePath); PrintWriter out = response.getWriter(); out.print("HHHHHHHHHH"); out.close(); out = null; } }
在此servlet中
（1）接收serverId
（2）调用临时素材业务类的方法TempMaterialService.getTempMaterial(accessToken, mediaId,savePath)，获取临时素材。
2.2 临时素材业务类—TempMaterialService
package com.ray.service; import java.io.File; import java.io.UnsupportedEncodingException; import com.ray.util.WeiXinUtil; import net.sf.json.JSONObject; /**@desc : 临时素材业务类 * * @author: shirayner * @date : 2017-8-18 下午2:07:25 */ public class TempMaterialService { //上传临时素材url public String uploadTempMaterial_url="https://qyapi.weixin.qq.com/cgi-bin/media/upload?access_token=ACCESS_TOKEN&type=TYPE"; //获取临时素材url public String getTempMaterial_url="https://qyapi.weixin.qq.com/cgi-bin/media/get?access_token=ACCESS_TOKEN&media_id=MEDIA_ID"; /** * @desc ：上传临时素材 * * @param accessToken 接口访问凭证 * @param type 媒体文件类型，分别有图片（image）、语音（voice）、视频（video），普通文件(file) * @param fileUrl 本地文件的url。例如 "D/1.img"。 * @return JSONObject 上传成功后，微信服务器返回的参数，有type、media_id 、created_at */ public JSONObject uploadTempMaterial(String accessToken,String type,String fileUrl){ //1.创建本地文件 File file=new File(fileUrl); //2.拼接请求url uploadTempMaterial_url = uploadTempMaterial_url.replace("ACCESS_TOKEN", accessToken) .replace("TYPE", type); //3.调用接口，发送请求，上传文件到微信服务器 String result=WeiXinUtil.httpRequest(uploadTempMaterial_url, file); //4.json字符串转对象：解析返回值，json反序列化 result = result.replaceAll("[\\\\]", ""); System.out.println("result:" + result); JSONObject resultJSON = JSONObject.fromObject(result); //5.返回参数判断 if (resultJSON != null) { if (resultJSON.get("media_id") != null) { System.out.println("上传" + type + "临时素材成功:"+resultJSON.get("media_id")); return resultJSON; } else { System.out.println("上传" + type + "临时素材成功失败"); } } return null; } /** 2.获取临时素材 * * @param accessToken * @param mediaId * @return * @throws UnsupportedEncodingException */ public void getTempMaterial(String accessToken,String mediaId,String savePath) throws UnsupportedEncodingException{ //String savePath=System.getProperty("user.dir").replaceAll("\\\\", "/")+"/WebContent/img/"+mediaId+".png"; //System.out.println("service savePath:"+savePath); //1.拼接请求url getTempMaterial_url=getTempMaterial_url.replace("ACCESS_TOKEN", accessToken) .replace("MEDIA_ID", mediaId); savePath=savePath+mediaId; //2.调用接口，发送请求，获取临时素材 File file=null; try { file = WeiXinUtil.getFile(getTempMaterial_url,savePath); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } System.out.println("file:"+file.getName()); } }
在此类的获取临时素材方法中：
（1）拼接微信获取临时素材的接口url
（2）调用WeiXinUtil.getFile(getTempMaterial_url,savePath)，向微信发起https请求，并将接收到的图片下载到savePath指定的路径下
2.3 微信工具类—WeiXinUtil
package com.ray.util; import java.io.BufferedReader; import java.io.DataInputStream; import java.io.DataOutputStream; import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.OutputStream; import java.io.UnsupportedEncodingException; import java.net.ConnectException; import java.net.HttpURLConnection; import java.net.URL; 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 javax.net.ssl.HttpsURLConnection; import javax.net.ssl.SSLContext; import javax.net.ssl.SSLSocketFactory; import javax.net.ssl.TrustManager; import javax.servlet.http.HttpServletRequest; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import com.ray.pojo.AccessToken; import net.sf.json.JSONException; import net.sf.json.JSONObject; public class WeiXinUtil { private static Logger log = LoggerFactory.getLogger(WeiXinUtil.class); //微信的请求url //获取access_token的接口地址（GET） 限200（次/天） public final static String access_token_url = "https://qyapi.weixin.qq.com/cgi-bin/gettoken?corpid={corpId}&corpsecret={corpsecret}"; //获取jsapi_ticket的接口地址（GET） 限200（次/天） public final static String jsapi_ticket_url = "https://qyapi.weixin.qq.com/cgi-bin/get_jsapi_ticket?access_token=ACCESSTOKEN"; /** * 1.发起https请求并获取结果 * * @param requestUrl 请求地址 * @param requestMethod 请求方式（GET、POST） * @param outputStr 提交的数据 * @return JSONObject(通过JSONObject.get(key)的方式获取json对象的属性值) */ public static JSONObject httpRequest(String requestUrl, String requestMethod, String outputStr) { JSONObject jsonObject = null; StringBuffer buffer = new StringBuffer(); try { // 创建SSLContext对象，并使用我们指定的信任管理器初始化 TrustManager[] tm = { new MyX509TrustManager() }; SSLContext sslContext = SSLContext.getInstance("SSL", "SunJSSE"); sslContext.init(null, tm, new java.security.SecureRandom()); // 从上述SSLContext对象中得到SSLSocketFactory对象 SSLSocketFactory ssf = sslContext.getSocketFactory(); URL url = new URL(requestUrl); HttpsURLConnection httpUrlConn = (HttpsURLConnection) url.openConnection(); httpUrlConn.setSSLSocketFactory(ssf); httpUrlConn.setDoOutput(true); httpUrlConn.setDoInput(true); httpUrlConn.setUseCaches(false); // 设置请求方式（GET/POST） httpUrlConn.setRequestMethod(requestMethod); if ("GET".equalsIgnoreCase(requestMethod)) httpUrlConn.connect(); // 当有数据需要提交时 if (null != outputStr) { OutputStream outputStream = httpUrlConn.getOutputStream(); // 注意编码格式，防止中文乱码 outputStream.write(outputStr.getBytes("UTF-8")); outputStream.close(); } // 将返回的输入流转换成字符串 InputStream inputStream = httpUrlConn.getInputStream(); InputStreamReader inputStreamReader = new InputStreamReader(inputStream, "UTF-8"); BufferedReader bufferedReader = new BufferedReader(inputStreamReader); String str = null; while ((str = bufferedReader.readLine()) != null) { buffer.append(str); } bufferedReader.close(); inputStreamReader.close(); // 释放资源 inputStream.close(); inputStream = null; httpUrlConn.disconnect(); jsonObject = JSONObject.fromObject(buffer.toString()); } catch (ConnectException ce) { log.error("Weixin server connection timed out."); } catch (Exception e) { log.error("https request error:{}", e); } return jsonObject; } /** * 2.发送https请求之获取临时素材 * @param requestUrl * @param savePath 文件的保存路径，此时还缺一个扩展名 * @return * @throws Exception */ public static File getFile(String requestUrl,String savePath) throws Exception { //String path=System.getProperty("user.dir")+"/img//1.png"; // 创建SSLContext对象，并使用我们指定的信任管理器初始化 TrustManager[] tm = { new MyX509TrustManager() }; SSLContext sslContext = SSLContext.getInstance("SSL", "SunJSSE"); sslContext.init(null, tm, new java.security.SecureRandom()); // 从上述SSLContext对象中得到SSLSocketFactory对象 SSLSocketFactory ssf = sslContext.getSocketFactory(); URL url = new URL(requestUrl); HttpsURLConnection httpUrlConn = (HttpsURLConnection) url.openConnection(); httpUrlConn.setSSLSocketFactory(ssf); httpUrlConn.setDoOutput(true); httpUrlConn.setDoInput(true); httpUrlConn.setUseCaches(false); // 设置请求方式（GET/POST） httpUrlConn.setRequestMethod("GET"); httpUrlConn.connect(); //获取文件扩展名 String ext=getExt(httpUrlConn.getContentType()); savePath=savePath+ext; System.out.println("savePath"+savePath); //下载文件到f文件 File file = new File(savePath); // 获取微信返回的输入流 InputStream in = httpUrlConn.getInputStream(); //输出流，将微信返回的输入流内容写到文件中 FileOutputStream out = new FileOutputStream(file); int length=100*1024; byte[] byteBuffer = new byte[length]; //存储文件内容 int byteread =0; int bytesum=0; while (( byteread=in.read(byteBuffer)) != -1) { bytesum += byteread; //字节数 文件大小 out.write(byteBuffer,0,byteread); } System.out.println("bytesum: "+bytesum); in.close(); // 释放资源 out.close(); in = null; out=null; httpUrlConn.disconnect(); return file; } /** * @desc ：2.微信上传素材的请求方法 * * @param requestUrl 微信上传临时素材的接口url * @param file 要上传的文件 * @return String 上传成功后，微信服务器返回的消息 */ public static String httpRequest(String requestUrl, File file) { StringBuffer buffer = new StringBuffer(); try{ //1.建立连接 URL url = new URL(requestUrl); HttpURLConnection httpUrlConn = (HttpURLConnection) url.openConnection(); //打开链接 //1.1输入输出设置 httpUrlConn.setDoInput(true); httpUrlConn.setDoOutput(true); httpUrlConn.setUseCaches(false); // post方式不能使用缓存 //1.2设置请求头信息 httpUrlConn.setRequestProperty("Connection", "Keep-Alive"); httpUrlConn.setRequestProperty("Charset", "UTF-8"); //1.3设置边界 String BOUNDARY = "----------" + System.currentTimeMillis(); httpUrlConn.setRequestProperty("Content-Type","multipart/form-data; boundary="+ BOUNDARY); // 请求正文信息 // 第一部分： //2.将文件头输出到微信服务器 StringBuilder sb = new StringBuilder(); sb.append("--"); // 必须多两道线 sb.append(BOUNDARY); sb.append("\r\n"); sb.append("Content-Disposition: form-data;name=\"media\";filelength=\"" + file.length() + "\";filename=\""+ file.getName() + "\"\r\n"); sb.append("Content-Type:application/octet-stream\r\n\r\n"); byte[] head = sb.toString().getBytes("utf-8"); // 获得输出流 OutputStream outputStream = new DataOutputStream(httpUrlConn.getOutputStream()); // 将表头写入输出流中：输出表头 outputStream.write(head); //3.将文件正文部分输出到微信服务器 // 把文件以流文件的方式 写入到微信服务器中 DataInputStream in = new DataInputStream(new FileInputStream(file)); int bytes = 0; byte[] bufferOut = new byte[1024]; while ((bytes = in.read(bufferOut)) != -1) { outputStream.write(bufferOut, 0, bytes); } in.close(); //4.将结尾部分输出到微信服务器 byte[] foot = ("\r\n--" + BOUNDARY + "--\r\n").getBytes("utf-8");// 定义最后数据分隔线 outputStream.write(foot); outputStream.flush(); outputStream.close(); //5.将微信服务器返回的输入流转换成字符串 InputStream inputStream = httpUrlConn.getInputStream(); InputStreamReader inputStreamReader = new InputStreamReader(inputStream, "utf-8"); BufferedReader bufferedReader = new BufferedReader(inputStreamReader); String str = null; while ((str = bufferedReader.readLine()) != null) { buffer.append(str); } bufferedReader.close(); inputStreamReader.close(); // 释放资源 inputStream.close(); inputStream = null; httpUrlConn.disconnect(); } catch (IOException e) { System.out.println("发送POST请求出现异常！" + e); e.printStackTrace(); } return buffer.toString(); } /** * 2.发起http请求获取返回结果 * * @param requestUrl 请求地址 * @return */ public static String httpRequest(String requestUrl) { StringBuffer buffer = new StringBuffer(); try { URL url = new URL(requestUrl); HttpURLConnection httpUrlConn = (HttpURLConnection) url.openConnection(); httpUrlConn.setDoOutput(false); httpUrlConn.setDoInput(true); httpUrlConn.setUseCaches(false); httpUrlConn.setRequestMethod("GET"); httpUrlConn.connect(); // 将返回的输入流转换成字符串 InputStream inputStream = httpUrlConn.getInputStream(); //InputStreamReader inputStreamReader = new InputStreamReader(inputStream, "utf-8"); InputStreamReader inputStreamReader = new InputStreamReader(inputStream); BufferedReader bufferedReader = new BufferedReader(inputStreamReader); String str = null; while ((str = bufferedReader.readLine()) != null) { buffer.append(str); } bufferedReader.close(); inputStreamReader.close(); // 释放资源 inputStream.close(); inputStream = null; httpUrlConn.disconnect(); } catch (Exception e) { } return buffer.toString(); } /** * 3.获取access_token * * @param appid 凭证 * @param appsecret 密钥 * @return */ public static AccessToken getAccessToken(String appid, String appsecret) { AccessToken accessToken = null; String requestUrl = access_token_url.replace("{corpId}", appid).replace("{corpsecret}", appsecret); JSONObject jsonObject = httpRequest(requestUrl, "GET", null); // 如果请求成功 if (null != jsonObject) { try { accessToken = new AccessToken(); accessToken.setToken(jsonObject.getString("access_token")); accessToken.setExpiresIn(jsonObject.getInt("expires_in")); } catch (JSONException e) { accessToken = null; // 获取token失败 log.error("获取token失败 errcode:{} errmsg:{}", jsonObject.getInt("errcode"), jsonObject.getString("errmsg")); } } return accessToken; } /** * 4. 获取JsapiTicket * @param accessToken * @return */ public static String getJsapiTicket(String accessToken){ String requestUrl = jsapi_ticket_url.replace("ACCESSTOKEN", accessToken); JSONObject jsonObject = httpRequest(requestUrl, "GET", null); String jsapi_ticket=""; // 如果请求成功 if (null != jsonObject) { try { jsapi_ticket=jsonObject.getString("ticket"); } catch (JSONException e) { // 获取token失败 log.error("获取token失败 errcode:{} errmsg:{}", jsonObject.getInt("errcode"), jsonObject.getString("errmsg")); } } return jsapi_ticket; } /** * 3.获取企业微信的JSSDK配置信息 * @param request * @return */ public static Map<String, Object> getWxConfig(HttpServletRequest request) { Map<String, Object> ret = new HashMap<String, Object>(); //1.准备好参与签名的字段 String nonceStr = UUID.randomUUID().toString(); // 必填，生成签名的随机串 //System.out.println("nonceStr:"+nonceStr); String accessToken=WeiXinUtil.getAccessToken(WeiXinParamesUtil.corpId, WeiXinParamesUtil.agentSecret).getToken(); String jsapi_ticket =getJsapiTicket(accessToken);// 必填，生成签名的H5应用调用企业微信JS接口的临时票据 //System.out.println("jsapi_ticket:"+jsapi_ticket); String timestamp = Long.toString(System.currentTimeMillis() / 1000); // 必填，生成签名的时间戳 //System.out.println("timestamp:"+timestamp); String url=request.getRequestURL().toString(); //System.out.println("url:"+url); //2.字典序 ，注意这里参数名必须全部小写，且必须有序 String sign = "jsapi_ticket=" + jsapi_ticket + "&noncestr=" + nonceStr+ "×tamp=" + timestamp + "&url=" + url; //3.sha1签名 String signature = ""; try { MessageDigest crypt = MessageDigest.getInstance("SHA-1"); crypt.reset(); crypt.update(sign.getBytes("UTF-8")); signature = byteToHex(crypt.digest()); //System.out.println("signature:"+signature); } catch (NoSuchAlgorithmException e) { e.printStackTrace(); } catch (UnsupportedEncodingException e) { e.printStackTrace(); } ret.put("appId", WeiXinParamesUtil.corpId); ret.put("timestamp", timestamp); ret.put("nonceStr", nonceStr); ret.put("signature", signature); return ret; } /** * 方法名：byteToHex</br> * 详述：字符串加密辅助方法 </br> * 开发人员：souvc </br> * 创建时间：2016-1-5 </br> * @param hash * @return 说明返回值含义 * @throws 说明发生此异常的条件 */ 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; } private static String getExt(String contentType){ if("image/jpeg".equals(contentType)){ return ".jpg"; }else if("image/png".equals(contentType)){ return ".png"; }else if("image/gif".equals(contentType)){ return ".gif"; } return null; } }
获取临时素材的方法为：WeiXinUtil.getFile（String requestUrl,String savePath)
在此方法中：
（1）发起https请求，获取输入流
（2）从输入流中获取文件类型，与savePath一起组成图片最终的路径（或者说是文件名A）
（3）根据文件名A创建输出流
（4）将输入流中的数据写入到输出流中，这样图片就保存到了文件A中。
（5）返回文件A
