回复图片、音频、视频消息都是需要media_id的，这个是需要将多媒体文件上传到微信服务器才有的。

将多媒体文件上传到微信服务器，以及从微信服务器下载文件，可以参考：http://mp.weixin.qq.com/wiki/index.php?title=上传下载多媒体文件

上传下载多媒体文件的方法还是写到WeixinUtil.java中。

代码如下：

import java.io.BufferedOutputStream;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.net.HttpURLConnection;import java.net.MalformedURLException;import java.net.URL;import java.security.KeyManagementException;import java.security.NoSuchAlgorithmException;import java.security.NoSuchProviderException;import java.security.SecureRandom;import java.util.Calendar;import java.util.Date;import java.util.HashMap;import java.util.Map;import javax.net.ssl.HttpsURLConnection;import javax.net.ssl.SSLContext;import javax.net.ssl.SSLSocketFactory;import javax.net.ssl.TrustManager;import net.sf.json.JSONObject;import org.apache.commons.lang.StringUtils;import org.apache.log4j.Logger;import com.company.project.model.menu.AccessToken;import com.company.project.model.menu.Menu;public class WeixinUtil { private static Logger log = Logger.getLogger(WeixinUtil.class); public final static String APPID = "wxb927d4280e6db674"; public final static String APP_SECRET = "21441e9f3226eee81e14380a768b6d1e"; // 获取access_token的接口地址（GET） 限200（次/天） public final static String access_token_url = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=APPID&secret=APPSECRET"; // 创建菜单 public final static String create_menu_url = "https://api.weixin.qq.com/cgi-bin/menu/create?access_token=ACCESS_TOKEN"; // 存放：1.token，2：获取token的时间,3.过期时间 public final static Map<String,Object> accessTokenMap = new HashMap<String,Object>(); /** * 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 handleRequest(String requestUrl,String requestMethod,String outputStr) { JSONObject jsonObject = null; try { URL url = new URL(requestUrl); HttpsURLConnection conn = (HttpsURLConnection) url.openConnection(); SSLContext ctx = SSLContext.getInstance("SSL", "SunJSSE"); TrustManager[] tm = {new MyX509TrustManager()}; ctx.init(null, tm, new SecureRandom()); SSLSocketFactory sf = ctx.getSocketFactory(); conn.setSSLSocketFactory(sf); conn.setDoInput(true); conn.setDoOutput(true); conn.setRequestMethod(requestMethod); conn.setUseCaches(false); if ("GET".equalsIgnoreCase(requestMethod)) { conn.connect(); } if (StringUtils.isNotEmpty(outputStr)) { OutputStream out = conn.getOutputStream(); out.write(outputStr.getBytes("utf-8")); out.close(); } InputStream in = conn.getInputStream(); BufferedReader br = new BufferedReader(new InputStreamReader(in,"utf-8")); StringBuffer buffer = new StringBuffer(); String line = null; while ((line = br.readLine()) != null) { buffer.append(line); } in.close(); conn.disconnect(); jsonObject = JSONObject.fromObject(buffer.toString()); } catch (MalformedURLException e) { e.printStackTrace(); log.error("URL错误！"); } catch (IOException e) { e.printStackTrace(); } catch (NoSuchAlgorithmException e) { e.printStackTrace(); } catch (NoSuchProviderException e) { e.printStackTrace(); } catch (KeyManagementException e) { e.printStackTrace(); } return jsonObject; } /** * 获取access_token * * @author qincd * @date Nov 6, 2014 9:56:43 AM */ public static AccessToken getAccessToken(String appid,String appSecret) { AccessToken at = new AccessToken(); // 每次获取access_token时，先从accessTokenMap获取，如果过期了就重新从微信获取 // 没有过期直接返回 // 从微信获取的token的有效期为2个小时 if (!accessTokenMap.isEmpty()) { Date getTokenTime = (Date) accessTokenMap.get("getTokenTime"); Calendar c = Calendar.getInstance(); c.setTime(getTokenTime); c.add(Calendar.HOUR_OF_DAY, 2); getTokenTime = c.getTime(); if (getTokenTime.after(new Date())) { log.info("缓存中发现token未过期，直接从缓存中获取access_token"); // token未过期，直接从缓存获取返回 String token = (String) accessTokenMap.get("token"); Integer expire = (Integer) accessTokenMap.get("expire"); at.setToken(token); at.setExpiresIn(expire); return at; } } String requestUrl = access_token_url.replace("APPID", appid).replace("APPSECRET", appSecret); JSONObject object = handleRequest(requestUrl, "GET", null); String access_token = object.getString("access_token"); int expires_in = object.getInt("expires_in"); log.info("\naccess_token:" + access_token); log.info("\nexpires_in:" + expires_in); at.setToken(access_token); at.setExpiresIn(expires_in); // 每次获取access_token后，存入accessTokenMap // 下次获取时，如果没有过期直接从accessTokenMap取。 accessTokenMap.put("getTokenTime", new Date()); accessTokenMap.put("token", access_token); accessTokenMap.put("expire", expires_in); return at; } /** * 创建菜单 * * @author qincd * @date Nov 6, 2014 9:56:36 AM */ public static boolean createMenu(Menu menu,String accessToken) { String requestUrl = create_menu_url.replace("ACCESS_TOKEN", accessToken); String menuJsonString = JSONObject.fromObject(menu).toString(); JSONObject jsonObject = handleRequest(requestUrl, "POST", menuJsonString); String errorCode = jsonObject.getString("errcode"); if (!"0".equals(errorCode)) { log.error(String.format("菜单创建失败！errorCode:%d,errorMsg:%s",jsonObject.getInt("errcode"),jsonObject.getString("errmsg"))); return false; } log.info("菜单创建成功！"); return true; } // 上传多媒体文件到微信服务器 public static final String upload_media_url = "http://file.api.weixin.qq.com/cgi-bin/media/upload?access_token=ACCESS_TOKEN&type=TYPE"; /** * 上传多媒体文件到微信服务器<br> * @see http:///cgi-bin/media/get?access_token=ACCESS_TOKEN&media_id=MEDIA_ID"; /** * 从微信服务器下载多媒体文件 * * @author qincd * @date Nov 6, 2014 4:32:12 PM */ public static String downloadMediaFromWx(String accessToken,String mediaId,String fileSavePath) throws IOException { if (StringUtils.isEmpty(accessToken) || StringUtils.isEmpty(mediaId)) return null; String requestUrl = download_media_url.replace("ACCESS_TOKEN", accessToken).replace("MEDIA_ID", mediaId); URL url = new URL(requestUrl); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); conn.setRequestMethod("GET"); conn.setDoInput(true); conn.setDoOutput(true); InputStream in = conn.getInputStream(); File dir = new File(fileSavePath); if (!dir.exists()) { dir.mkdirs(); } if (!fileSavePath.endsWith("/")) { fileSavePath += "/"; } String ContentDisposition = conn.getHeaderField("Content-disposition"); String weixinServerFileName = ContentDisposition.substring(ContentDisposition.indexOf("filename")+10, ContentDisposition.length() -1); fileSavePath += weixinServerFileName; BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(fileSavePath)); byte[] data = new byte[1024]; int len = -1; while ((len = in.read(data)) != -1) { bos.write(data,0,len); } bos.close(); in.close(); conn.disconnect(); return fileSavePath; }}

测试代码：

public class WeixinUtilTest { /** * * @author qincd * @date Nov 6, 2014 9:57:54 AM */ public static void main(String[] args) { // 1).获取access_token AccessToken accessToken = WeixinUtil.getAccessToken(WeixinUtil.APPID, WeixinUtil.APP_SECRET); String filePath = "C:\\Users\\qince\\Pictures\\壁纸20141029091612.jpg"; JSONObject uploadJsonObj = testUploadMedia(filePath,"image",accessToken.getToken()); if (uploadJsonObj == null) { System.out.println("上传图片失败"); return; } int errcode = 0; if (uploadJsonObj.containsKey("errcode")) { errcode = uploadJsonObj.getInt("errcode"); } if (errcode == 0) { System.out.println("图片上传成功"); String mediaId = uploadJsonObj.getString("media_id"); long createAt = uploadJsonObj.getLong("created_at"); System.out.println("--Details:"); System.out.println("media_id:" + mediaId); System.out.println("created_at:" + createAt); } else { System.out.println("图片上传失败！"); String errmsg = uploadJsonObj.getString("errmsg"); System.out.println("--Details:"); System.out.println("errcode:" + errcode); System.out.println("errmsg:" + errmsg); } String mediaId = "6W-UvSrQ2hkdSdVQJJXShwtFDPLfbGI1qnbNFy8weZyb9Jac2xxxcAUwt8p4sYPH"; String filepath = testDownloadMedia(accessToken.getToken(), mediaId, "d:/test"); System.out.println(filepath); } /** * 上传多媒体文件到微信 * * @author qincd * @date Nov 6, 2014 4:15:14 PM */ public static JSONObject testUploadMedia(String filePath,String type,String accessToken) { try { return WeixinUtil.uploadMediaToWX(filePath, type, accessToken); } catch (IOException e) { e.printStackTrace(); } return null; } /** * 从微信下载多媒体文件 * * @author qincd * @date Nov 6, 2014 4:56:25 PM */ public static String testDownloadMedia(String accessToken,String mediaId,String fileSaveDir) { try { return WeixinUtil.downloadMediaFromWx(accessToken, mediaId, fileSaveDir); } catch (IOException e) { e.printStackTrace(); } return null; }}

更多精彩内容请点击《Android微信开发教程汇总》，《java微信开发教程汇总》欢迎大家学习阅读。

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。