文件上传用的是Apache HttpClient 4.3。

    /**        * Example how to use multipart/form encoded POST request.        */        public class ClientMultipartFormPost {                    public static void main(String[] args) throws Exception {                if (args.length != 1)  {                    System.out.println("File path not given");                    System.exit(1);                }                CloseableHttpClient httpclient = HttpClients.createDefault();                try {                    HttpPost httppost = new HttpPost("http://localhost:8080" +                            "/servlets-examples/servlet/RequestInfoExample");                            FileBody img = new FileBody(new File(args[0]));                    StringBody filename = new StringBody("A binary file of some kind", ContentType.TEXT_PLAIN);                    StringBody comment = new StringBody("A binary file of some kind", ContentType.TEXT_PLAIN);                            HttpEntity reqEntity = MultipartEntityBuilder.create()                            .addPart("img", img)                            .addPart("filename", filename)                            .addPart("comment", comment)                            .build();                                    httppost.setEntity(reqEntity);                            System.out.println("executing request " + httppost.getRequestLine());                    CloseableHttpResponse response = httpclient.execute(httppost);                    try {                        System.out.println("----------------------------------------");                        System.out.println(response.getStatusLine());                        HttpEntity resEntity = response.getEntity();                        if (resEntity != null) {                            System.out.println("Response content length: " + resEntity.getContentLength());                        }                        EntityUtils.consume(resEntity);                    } finally {                        response.close();                    }                } finally {                    httpclient.close();                }            }                }