模拟浏览器post请求 用java写上传文件后台

公众号在使用接口时，对多媒体文件、多媒体消息的获取和调用等操作，是通过media_id来进行的。通过本接口，公众号可以上传或下载多媒体文件。但请注意，每个多媒体文件（media_id）会在上传、用户发送到微信服务器3天后自动删除，以节省服务器资源。

公众号可调用本接口来上传图片、语音、视频等文件到微信服务器，上传后服务器会返回对应的media_id，公众号此后可根据该media_id来获取多媒体。请注意，media_id是可复用的，调用该接口需http协议。

接口调用请求说明

 http请求方式: POST/FORM
 http://file.api.weixin.qq.com/cgi-bin/media/upload?access_token=ACCESS_TOKEN&type=TYPE
 调用示例（使用curl命令，用FORM表单方式上传一个多媒体文件）：
 curl -F [email protected] "http://file.api.weixin.qq.com/cgi-bin/media/upload?access_token=ACCESS_TOKEN&type=TYPE"

首先封装一个HttpPostUtil类，专门负责文件上传请求及一些参数的设置(此处可以理解为上传文件表单参数设置和connection的一些必须设置)、字符编码，文件类型等。

HttpPostUtil类代码：

 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 textParams = new HashMap();
     private HashMap fileparams = new HashMap();
     private DataOutputStream outputStream;

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

     /**
      * 重新设置要请求的服务器地址，即上传文件的地址。
      *
      * @param url
      * @throws Exception
      */
     public void setUrl(String url) throws Exception {
         this.url = new URL(url);
     }

     /**
      * 增加一个普通字符串数据到form表单数据中
      *
      * @param name
      * @param value
      */
     public void addParameter(String name, String value) {
         textParams.put(name, value);
     }

     /**
      * 增加一个文件到form表单数据中
      *
      * @param name
      * @param value
      */
     public void addParameter(String name, File value) {
         fileparams.put(name, value);
     }

     /**
      * 清空所有已添加的form表单数据
      */
     public void clearAllParameters() {
         textParams.clear();
         fileparams.clear();
     }

     /**
      * 发送数据到服务器，返回一个字节包含服务器的返回结果的数组
      *
      * @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;
     }

     /**
      * 文件上传的connection的一些必须设置
      *
      * @throws Exception
      */
     private void initConnection() throws Exception {
         conn = (HttpURLConnection) this.url.openConnection();
         conn.setDoOutput(true);
         conn.setUseCaches(false);
         conn.setConnectTimeout(10000); // 连接超时为10秒
         conn.setRequestMethod("POST");
         conn.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary);
     }

     /**
      * 普通字符串数据
      *
      * @throws Exception
      */
     private void writeStringParams() throws Exception {
         Set keySet = textParams.keySet();
         for (Iterator 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");
         }
     }

     /**
      * 文件数据
      *
      * @throws Exception
      */
     private void writeFileParams() throws Exception {
         Set keySet = fileparams.keySet();
         for (Iterator 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");
         }
     }

     /**
      * 获取文件的上传类型，图片格式为image/png,image/jpeg等。非图片为application /octet-stream
      *
      * @param f
      * @return
      * @throws Exception
      */
     private String getContentType(File f) throws Exception {
         return "application/octet-stream";
     }

     /**
      * 把文件转换成字节数组
      *
      * @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();
     }

     /**
      * 添加结尾数据
      *
      * @throws Exception
      */
     private void paramsEnd() throws Exception {
         outputStream.writeBytes("--" + boundary + "--" + "\r\n");
         outputStream.writeBytes("\r\n");
     }

     /**
      * 对包含中文的字符串进行转码，此为UTF-8。服务器那边要进行一次解码
      *
      * @param value
      * @return
      * @throws Exception
      */
     private String encode(String value) throws Exception {
         return URLEncoder.encode(value, "UTF-8");
     }
 }

上传测试方法（可以在自己项目中上传文件到一些第三方提供的平台）：

 /**
  * 使用方法示例
  * 此方法需要修改成自己上传地址才可上传成功
  * @param args
  * @throws Exception
  */
 public static void test(String[] args) throws Exception {
     File file=new File("D\\up.jpg");
     //此处修改为自己上传文件的地址
     HttpPostUtil post = new HttpPostUtil("http://www.omsdn.cn");
     //此处参数类似 curl -F [email protected]
     post.addParameter("media", file);
     post.send();
 }

上传文件方法封装好后，微信公众号上传文件类调用,此处需要JSON包（json-lib-2.2.3-jdk13.jar）：

 import java.io.File;
 import cn."font-family:FangSong_GB2312;">xx.wechat.model.MdlUpload;
 import cn."font-family:FangSong_GB2312;">xx.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";

     /**
      * 上传文件
      *
      * @param accessToken
      * @param type
      * @param file
      * @return
      */
     public static Result Upload(String accessToken, String type, File file) {
         Result result = new Result();
         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;
     }
 }

调用方法需要引用2个Model类（返回结果类和上传文件类型类）：

返回结果类：

 package cn."font-family:FangSong_GB2312;">xx.wechat.model;

 public class Result {
     private T obj;
     private String errcode;
     private String errmsg;
     public T getObj() {
         return obj;
     }
     public void setObj(T obj) {
         this.obj = obj;
     }
 "font-family:FangSong_GB2312;">        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;
     }

 }

文件上传返回文件类型类：

 package cn."font-family:FangSong_GB2312;">xx.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 + "]";
      }


 }

最后微信上传文件测试方法：

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

测试结果：