本文要用java.net.HttpURLConnection来实现多个文件上传
1. 研究 form 表单到底封装了什么样的信息发送到servlet。
假如我参数写的内容是hello word,然后二个文件是二个简单的txt文件，form提交的信息为：
- -----------------------------7da2e536604c8
- Content-Disposition: form-data; name="username"
- hello word
- -----------------------------7da2e536604c8
- Content-Disposition: form-data; name="file1"; filename="D:/haha.txt"
- Content-Type: text/plain
- haha
- hahaha
- -----------------------------7da2e536604c8
- Content-Disposition: form-data; name="file2"; filename="D:/huhu.txt"
- Content-Type: text/plain
- messi
- huhu
- -----------------------------7da2e536604c8--
研究下规律发现有如下几点特征
1.第一行是“ -----------------------------7d92221b604bc ”作为分隔符，然后是“ /r/n ” 回车换行符。 这个7d92221b604bc 分隔符浏览器是随机生成的。
2.第二行是Content-Disposition: form-data; name="file2"; filename="D:/huhu.txt";name=对应input的name值，filename对应要上传的文件名（包括路径在内），
3.第三行如果是文件就有Content-Type: text/plain；这里上传的是txt文件所以是text/plain,如果上穿的是jpg图片的话就是image/jpg了，可以自己试试看看。
然后就是回车换行符。
4.在下就是文件或参数的内容或值了。如：hello word。
5.最后一行是-----------------------------7da2e536604c8--,注意最后多了二个--;
有了这些就可以使用HttpURLConnection来实现上传文件功能了
- private void upload(String[] uploadFiles, String actionUrl) {
- String end = "/r/n";
- String twoHyphens = "--";
- String boundary = "*****";
- try {
- URL url = new URL(actionUrl);
- HttpURLConnection con = (HttpURLConnection) url.openConnection();
- // 发送POST请求必须设置如下两行
- con.setDoInput(true);
- con.setDoOutput(true);
- con.setUseCaches(false);
- con.setRequestMethod("POST");
- con.setRequestProperty("Connection", "Keep-Alive");
- con.setRequestProperty("Charset", "UTF-8");
- con.setRequestProperty("Content-Type",
- "multipart/form-data;boundary=" + boundary);
- DataOutputStream ds =
- new DataOutputStream(con.getOutputStream());
- for (int i = 0; i < uploadFiles.length; i++) {
- String uploadFile = uploadFiles[i];
- String filename = uploadFile.substring(uploadFile.lastIndexOf("//") + 1);
- ds.writeBytes(twoHyphens + boundary + end);
- ds.writeBytes("Content-Disposition: form-data; " +
- "name=/"file" + i + "/";filename=/"" +
- filename + "/"" + end);
- ds.writeBytes(end);
- FileInputStream fStream = new FileInputStream(uploadFile);
- int bufferSize = 1024;
- byte[] buffer = new byte[bufferSize];
- int length = -1;
- while ((length = fStream.read(buffer)) != -1) {
- ds.write(buffer, 0, length);
- }
- ds.writeBytes(end);
- /* close streams */
- fStream.close();
- }
- ds.writeBytes(twoHyphens + boundary + twoHyphens + end);
- ds.flush();
- // 定义BufferedReader输入流来读取URL的响应
- InputStream is = con.getInputStream();
- int ch;
- StringBuffer b = new StringBuffer();
- while ((ch = is.read()) != -1) {
- b.append((char) ch);
- }
- String s = b.toString();
- if (s.contains("successfully")) {
- // for (int i = 1; i < 5; i++) {
- int beginIndex = s.indexOf("url =") + 5;
- int endIndex = s.indexOf("/n", beginIndex);
- String urlStr = s.substring(beginIndex, endIndex).trim();
- System.out.println(urlStr);
- // }
- }
- ds.close();
- } catch (Exception e) {
- }
- }