使用java HTTP POST连接发送图像文件 [英] Send image file using java HTTP POST connections

问题描述

我正在尝试使用Java HTTP POST请求将图像发送到网站。

I'm trying to send an image to a website using Java HTTP POST requests.

我正在使用此处使用的基本代码将文件从Java客户端上传到HTTP服务器：

I'm using the base code used here Upload files from Java client to a HTTP server:

这个是我的修改：

String urlToConnect = "http://localhost:9000/upload";
File fileToUpload = new File("C:\\Users\\joao\\Pictures\\bla.jpg");
String boundary = Long.toHexString(System.currentTimeMillis()); // Just generate some unique random value.

URLConnection connection = new URL(urlToConnect).openConnection();
connection.setDoOutput(true); // This sets request method to POST.
connection.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary);
PrintWriter writer = null;
try {
    writer = new PrintWriter(new OutputStreamWriter(connection.getOutputStream()));
    writer.println("--" + boundary);
    writer.println("Content-Disposition: form-data; name=\"picture\"; filename=\"bla.jpg\"");
    writer.println("Content-Type: image/jpeg");
    writer.println();
    BufferedReader reader = null;
    try {
        reader = new BufferedReader(new InputStreamReader(new FileInputStream(fileToUpload)));
        for (String line; (line = reader.readLine()) != null;) {
            writer.println(line);
        }
    } finally {
        if (reader != null) try { reader.close(); } catch (IOException logOrIgnore) {}
    }
    writer.println("--" + boundary + "--");
} finally {
    if (writer != null) writer.close();
}

// Connection is lazily executed whenever you request any status.
int responseCode = ((HttpURLConnection) connection).getResponseCode();
System.out.println(responseCode); // Should be 200

我最后获得了200个响应代码，但图像有问题，就像在随机颜色中一样，这让我觉得它在字符编码中是一个错误。我尝试使用原始示例中的UTF-8，但这只会创建一个损坏的图像。

I get a 200 response code in the end, but the image is buggy, as in, random colors, which make me think it's an error in character encoding. I tried using UTF-8 as in the original example, but that just creates a corrupt image.

我也100％确定它不是服务器端问题，因为我可以使用其他客户端，例如Advanced Rest Client / Postman，他们可以毫无问题地发送图像。

I am also 100% sure it's not a serverside problem, because I can use rest clients such as Advanced Rest Client/Postman and they can send an image with no problems.

你能帮我查明错误吗？谢谢。

Can you help me pinpoint what's wrong? Thank you.

推荐答案

import java.io.File;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.HttpVersion;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.mime.MultipartEntity;
import org.apache.http.entity.mime.content.ContentBody;
import org.apache.http.entity.mime.content.FileBody;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.params.CoreProtocolPNames;
import org.apache.http.util.EntityUtils;


public class PostFile {
  public static void main(String[] args) throws Exception {
    HttpClient httpclient = new DefaultHttpClient();
    httpclient.getParams().setParameter(CoreProtocolPNames.PROTOCOL_VERSION, HttpVersion.HTTP_1_1);

    HttpPost httppost = new HttpPost("http://localhost:9000/upload");
    File file = new File("C:\\Users\\joao\\Pictures\\bla.jpg"");

    MultipartEntity mpEntity = new MultipartEntity();
    ContentBody cbFile = new FileBody(file, "image/jpeg");
    mpEntity.addPart("userfile", cbFile);


    httppost.setEntity(mpEntity);
    System.out.println("executing request " + httppost.getRequestLine());
    HttpResponse response = httpclient.execute(httppost);
    HttpEntity resEntity = response.getEntity();

    System.out.println(response.getStatusLine());
    if (resEntity != null) {
      System.out.println(EntityUtils.toString(resEntity));
    }
    if (resEntity != null) {
      resEntity.consumeContent();
    }

    httpclient.getConnectionManager().shutdown();
  }
}

使用 HttpClient 来计算出这段代码。呃使用稳定的库而不是从头开始处理，除非有自定义方式处理。

Use HttpClient to work out this code. Its always better to use stable libraries other than handling from scratch, unless there is something to be handled in custom way.

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