如何在Http POST请求中发送图像文件？ （JAVA）

Question

所以我写一个小程序来转储映像到用户的tumblr博客的目录中，使用其提供的API：http://www.tumblr.com/docs/en/api

我已经得到明文张贴工作，但现在我需要找到了解如何在POST中发送图像文件而不是UTF-8编码文本，并且我迷路了。我的代码此刻正在返回一个403禁止的错误，就好像用户名和密码不正确（他们不是），而我尝试的其他所有内容都会给我一个错误的请求错误。如果可以的话，我宁愿不必为此使用外部库。这是我的ImagePost类：

public class ImagePost { 

String data = null; 
String enc = "UTF-8"; 
String type; 
File img; 

public ImagePost(String imgPath, String caption, String tags) throws IOException { 

    //Construct data 
    type = "photo"; 
    img = new File(imgPath); 

    data = URLEncoder.encode("email", enc) + "=" + URLEncoder.encode(Main.getEmail(), enc); 
    data += "&" + URLEncoder.encode("password", enc) + "=" + URLEncoder.encode(Main.getPassword(), enc); 
    data += "&" + URLEncoder.encode("type", enc) + "=" + URLEncoder.encode(type, enc); 
    data += "&" + URLEncoder.encode("data", enc) + "=" + img; 
    data += "&" + URLEncoder.encode("caption", enc) + "=" + URLEncoder.encode(caption, enc); 
    data += "&" + URLEncoder.encode("generator", "UTF-8") + "=" + URLEncoder.encode(Main.getVersion(), "UTF-8"); 
    data += "&" + URLEncoder.encode("tags", "UTF-8") + "=" + URLEncoder.encode(tags, "UTF-8"); 

} 

public void send() throws IOException { 
    // Set up connection 
    URL tumblrWrite = new URL("http://www.tumblr.com/api/write"); 
    HttpURLConnection http = (HttpURLConnection) tumblrWrite.openConnection(); 
    http.setDoOutput(true); 
    http.setRequestMethod("POST"); 
    http.setRequestProperty("Content-Type", "image/png"); 
    DataOutputStream dout = new DataOutputStream(http.getOutputStream()); 
    //OutputStreamWriter out = new OutputStreamWriter(http.getOutputStream()); 

    // Send data 
    http.connect(); 
    dout.writeBytes(data); 
    //out.write(data); 
    dout.flush(); 
    System.out.println(http.getResponseCode()); 
    System.out.println(http.getResponseMessage()); 
    dout.close(); 
} 
} 

Answer 1

我建议你使用MultipartRequestEntity（不建议使用MultipartPostMethod的继任者）在Apache httpclient包。通过MultipartRequestEntity，您可以发送包含文件的多部分POST请求。示例如下：

public static void postData(String urlString, String filePath) { 

    log.info("postData"); 
    try { 
     File f = new File(filePath); 
     PostMethod postMessage = new PostMethod(urlString); 
     Part[] parts = { 
       new StringPart("param_name", "value"), 
       new FilePart(f.getName(), f) 
     }; 
     postMessage.setRequestEntity(new MultipartRequestEntity(parts, postMessage.getParams())); 
     HttpClient client = new HttpClient(); 

     int status = client.executeMethod(postMessage); 
    } catch (HttpException e) { 
     // TODO Auto-generated catch block 
     e.printStackTrace(); 
    } catch (IOException e) { 
     // TODO Auto-generated catch block 
     e.printStackTrace(); 
    }   
}