公眾號在使用介面時，對多媒體檔案、多媒體訊息的獲取和呼叫等操作，是通過media_id來進行的。通過本介面，公眾號可以上傳或下載多媒體檔案。但請注意，每個多媒體檔案（media_id）會在上傳、使用者傳送到微信伺服器3天后自動刪除，以節省伺服器資源。

公眾號可呼叫本介面來上傳圖片、語音、視訊等檔案到微信伺服器，上傳後伺服器會返回對應的media_id，公眾號此後可根據該media_id來獲取多媒體。請注意，media_id是可複用的，呼叫該介面需http協議。

介面呼叫請求說明

http請求方式: POST/FORM
http://file.api.weixin.qq.com/cgi-bin/media/upload?access_token=ACCESS_TOKEN&type=TYPE
呼叫示例（使用curl命令，用FORM表單方式上傳一個多媒體檔案）：
curl -F 
 
[email protected] "http://file.api.weixin.qq.com/cgi-bin/media/upload?access_token=ACCESS_TOKEN&type=TYPE"

首先封裝一個HttpPostUtil類，專門負責檔案上傳請求及一些引數的設定(此處可以理解為上傳檔案表單引數設定和connection的一些必須設定)、字元編碼，檔案型別等。

HttpPostUtil類程式碼：

import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Set;

/**
 * 
 * @author Sunlight
 * 
 */
public class HttpPostUtil {
	private URL url;
	private HttpURLConnection conn;
	private String boundary = "--------httppost123";
	private HashMap<String, String> textParams = new HashMap<String, String>();
	private HashMap<String, File> fileparams = new HashMap<String, File>();
	private DataOutputStream outputStream;

	public HttpPostUtil(String url) throws Exception {
		this.url = new URL(url);
	}

	/**
	 * 重新設定要請求的伺服器地址，即上傳檔案的地址。
	 * 
	 * @param url
	 * @throws Exception
	 */
	public void setUrl(String url) throws Exception {
		this.url = new URL(url);
	}

	/**
	 * 增加一個普通字串資料到form表單資料中
	 * 
	 * @param name
	 * @param value
	 */
	public void addParameter(String name, String value) {
		textParams.put(name, value);
	}

	/**
	 * 增加一個檔案到form表單資料中
	 * 
	 * @param name
	 * @param value
	 */
	public void addParameter(String name, File value) {
		fileparams.put(name, value);
	}

	/**
	 * 清空所有已新增的form表單資料
	 */
	public void clearAllParameters() {
		textParams.clear();
		fileparams.clear();
	}

	/**
	 * 傳送資料到伺服器，返回一個位元組包含伺服器的返回結果的陣列
	 * 
	 * @return
	 * @throws Exception
	 */
	public String send() throws Exception {
		initConnection();
		conn.connect();
		outputStream = new DataOutputStream(conn.getOutputStream());
		writeFileParams();
		writeStringParams();
		paramsEnd();
		int code = conn.getResponseCode();
		if (code == 200) {
			InputStream in = conn.getInputStream();
			ByteArrayOutputStream out = new ByteArrayOutputStream();
			byte[] buf = new byte[1024 * 8];
			int len;
			while ((len = in.read(buf)) != -1) {
				out.write(buf, 0, len);
			}
			conn.disconnect();
			String s = new String(out.toByteArray(), "utf-8");
			return s;
		}
		return null;
	}

	/**
	 * 檔案上傳的connection的一些必須設定
	 * 
	 * @throws Exception
	 */
	private void initConnection() throws Exception {
		conn = (HttpURLConnection) this.url.openConnection();
		conn.setDoOutput(true);
		conn.setUseCaches(false);
		conn.setConnectTimeout(10000); // 連線超時為10秒
		conn.setRequestMethod("POST");
		conn.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary);
	}

	/**
	 * 普通字串資料
	 * 
	 * @throws Exception
	 */
	private void writeStringParams() throws Exception {
		Set<String> keySet = textParams.keySet();
		for (Iterator<String> it = keySet.iterator(); it.hasNext();) {
			String name = it.next();
			String value = textParams.get(name);
			outputStream.writeBytes("--" + boundary + "\r\n");
			outputStream.writeBytes("Content-Disposition: form-data; name=\"" + name + "\"\r\n");
			outputStream.writeBytes("\r\n");
			outputStream.writeBytes(encode(value) + "\r\n");
		}
	}

	/**
	 * 檔案資料
	 * 
	 * @throws Exception
	 */
	private void writeFileParams() throws Exception {
		Set<String> keySet = fileparams.keySet();
		for (Iterator<String> it = keySet.iterator(); it.hasNext();) {
			String name = it.next();
			File value = fileparams.get(name);
			outputStream.writeBytes("--" + boundary + "\r\n");
			outputStream.writeBytes("Content-Disposition: form-data; name=\"" + name + "\"; filename=\"" + encode(value.getName()) + "\"\r\n");
			outputStream.writeBytes("Content-Type: " + getContentType(value) + "\r\n");
			outputStream.writeBytes("\r\n");
			outputStream.write(getBytes(value));
			outputStream.writeBytes("\r\n");
		}
	}

	/**
	 * 獲取檔案的上傳型別，圖片格式為image/png,image/jpeg等。非圖片為application /octet-stream
	 * 
	 * @param f
	 * @return
	 * @throws Exception
	 */
	private String getContentType(File f) throws Exception {
		return "application/octet-stream";
	}

	/**
	 * 把檔案轉換成位元組陣列
	 * 
	 * @param f
	 * @return
	 * @throws Exception
	 */
	private byte[] getBytes(File f) throws Exception {
		FileInputStream in = new FileInputStream(f);
		ByteArrayOutputStream out = new ByteArrayOutputStream();
		byte[] b = new byte[1024];
		int n;
		while ((n = in.read(b)) != -1) {
			out.write(b, 0, n);
		}
		in.close();
		return out.toByteArray();
	}

	/**
	 * 新增結尾資料
	 * 
	 * @throws Exception
	 */
	private void paramsEnd() throws Exception {
		outputStream.writeBytes("--" + boundary + "--" + "\r\n");
		outputStream.writeBytes("\r\n");
	}

	/**
	 * 對包含中文的字串進行轉碼，此為UTF-8。伺服器那邊要進行一次解碼
	 * 
	 * @param value
	 * @return
	 * @throws Exception
	 */
	private String encode(String value) throws Exception {
		return URLEncoder.encode(value, "UTF-8");
	}	
}
 

/**
 * 使用方法示例
 * 此方法需要修改成自己上傳地址才可上傳成功
 * @param args
 * @throws Exception
 */
public static void test(String[] args) throws Exception {
	File file=new File("D\\up.jpg");
	//此處修改為自己上傳檔案的地址
	HttpPostUtil post = new HttpPostUtil("http://www.omsdn.cn"); 
	//此處引數類似 curl -F [email protected]
 

	post.addParameter("media", file);
	post.send();
}

上傳檔案方法封裝好後，微信公眾號上傳檔案類呼叫,此處需要JSON包（json-lib-2.2.3-jdk13.jar）：

import java.io.File;
import cn.<span style="font-family:FangSong_GB2312;">xx</span>.wechat.model.MdlUpload;
import cn.<span style="font-family:FangSong_GB2312;">xx</span>.wechat.model.Result;
import net.sf.json.JSONObject;
/**
 * 
 * @author Sunlight
 *
 */
public class FileUpload {
    private static final String upload_url = "https://qyapi.weixin.qq.com/cgi-bin/media/upload?access_token=ACCESS_TOKEN&type=TYPE";
    
    /**
     * 上傳檔案
     * 
     * @param accessToken
     * @param type
     * @param file
     * @return
     */
    public static Result<MdlUpload> Upload(String accessToken, String type, File file) {
        Result<MdlUpload> result = new Result<MdlUpload>();
        String url = upload_url.replace("ACCESS_TOKEN", accessToken).replace("TYPE", type);
        JSONObject jsonObject;
        try {
            HttpPostUtil post = new HttpPostUtil(url);
            post.addParameter("media", file);
            String s = post.send();
            jsonObject = JSONObject.fromObject(s);
            if (jsonObject.containsKey("media_id")) {
                MdlUpload upload=new MdlUpload();
                upload.setMedia_id(jsonObject.getString("media_id"));
                upload.setType(jsonObject.getString("type"));
                upload.setCreated_at(jsonObject.getString("created_at"));
                result.setObj(upload);
                result.setErrmsg("success");
                result.setErrcode("0");
            } else {
                result.setErrmsg(jsonObject.getString("errmsg"));
                result.setErrcode(jsonObject.getString("errcode"));
            }
        } catch (Exception e) {
            e.printStackTrace();
            result.setErrmsg("Upload Exception:"+e.toString());
        }
        return result;
    }
}

返回結果類：

package cn.<span style="font-family:FangSong_GB2312;">xx</span>.wechat.model;

public class Result<T> {
	private T obj;
	private String errcode;
	private String errmsg;
	public T getObj() {
		return obj;
	}
	public void setObj(T obj) {
		this.obj = obj;
	}
<span style="font-family:FangSong_GB2312;">        </span>public String getErrcode() {
		return errcode;
	}
	 public void setErrcode(String errcode) {
		 this.errcode = errcode;
	 }
 	public String getErrmsg() {
		 return errmsg;
 	}
 	public void setErrmsg(String errmsg) {
		 this.errmsg = errmsg;
 	}
	
}

package cn.<span style="font-family:FangSong_GB2312;">xx</span>.wechat.model;

public class MdlUpload {
 	private String type;
	private String media_id;
	private String created_at;
  	public String getType() {
  		return type;
	}
	  public void setType(String type) {
		 this.type = type;
	  }
 	public String getMedia_id() {
		  return media_id;
  	}
	 public void setMedia_id(String mediaId) {
		  media_id = mediaId;
  	}
 	public String getCreated_at() {
		  return created_at;
	  }
	 public void setCreated_at(String createdAt) {
		  created_at = createdAt;
 	}
	  public MdlUpload() {
		 super();
	 }
	@Override
	public String toString() {
 		return "MdlUpload [created_at=" + created_at + ", media_id=" + media_id + ", type=" + type + "]";
	 }
	
	
}

@Test
    public void testUpload() {
        File file=new File("E:\\Tulips.jpg");
        System.err.println(file.getName());
        Result<MdlUpload> result=FileUpload .Upload("image", file);
        System.out.println("Errcode="+result.getErrcode()+"\tErrmsg="+result.getErrmsg());
        System.out.println(result.getObj().toString());
    }