首先对我在评论中发布的示例感到抱歉。POST我以为您只是通过提交一些值来尝试执行一个简单的请求。我错过了您也在上传文件。因此，由于您还上传了一个文件（请注意，您不只是在此处传递文件名），这是一个多部分请求（您可以在 jsp: 中看到enctype="multipart/form-data"），并且它需要以编程方式完成更多工作。
当您提交多部分表单时，请求如下所示：
-----------------------------253171262814565
Content-Disposition: form-data; name="myfile"; filename="test.bin"
Content-Type: application/octet-stream
Test data
-----------------------------253171262814565
Content-Disposition: form-data; name="submit"
Submit
-----------------------------253171262814565--
这种奇怪的字母数字称为边界（由浏览器随机选择），用于区分提交的字段（文件或普通字段）。在上面的示例中，提交的字段是：
- 表单中名为“myfile”的字段
<input type="file">。用户选择了名为test.bin. 文件数据是单个文本行Test data
- 按钮
"Submit"的正常字段值<input type="submit">
下面我从code.java.net 的示例中复制了代码，该示例提供了一个可以帮助您创建此类请求的类。
请修改任何硬编码的 url 和文件以匹配您的情况。我还没有尝试过，但它应该让你知道如何创建一个像上面这样的请求。（注意有两个类：一个构造请求，一个带有main()测试它的方法）
旁注：行字符的变化\r\n不依赖于系统，但它是多部分请求构造的一部分。因此，无论您的系统是 Windows 还是 Linux，都应该按原样使用它
我希望这会有所帮助
package net.codejava.networking;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.List;
/**
* This utility class provides an abstraction layer for sending multipart HTTP
* POST requests to a web server.
* @author www.codejava.net
*
*/
public class MultipartUtility {
private final String boundary;
private static final String LINE_FEED = "\r\n";
private HttpURLConnection httpConn;
private String charset;
private OutputStream outputStream;
private PrintWriter writer;
/**
* This constructor initializes a new HTTP POST request with content type
* is set to multipart/form-data
* @param requestURL
* @param charset
* @throws IOException
*/
public MultipartUtility(String requestURL, String charset)
throws IOException {
this.charset = charset;
// creates a unique boundary based on time stamp
boundary = "===" + System.currentTimeMillis() + "===";
URL url = new URL(requestURL);
httpConn = (HttpURLConnection) url.openConnection();
httpConn.setDoOutput(true); // indicates POST method
httpConn.setDoInput(true);
httpConn.setRequestProperty("Content-Type",
"multipart/form-data; boundary=" + boundary);
outputStream = httpConn.getOutputStream();
writer = new PrintWriter(new OutputStreamWriter(outputStream, charset),
true);
}
/**
* Adds a form field to the request
* @param name field name
* @param value field value
*/
public void addFormField(String name, String value) {
writer.append("--" + boundary).append(LINE_FEED);
writer.append("Content-Disposition: form-data; name=\"" + name + "\"")
.append(LINE_FEED);
writer.append("Content-Type: text/plain; charset=" + charset).append(
LINE_FEED);
writer.append(LINE_FEED);
writer.append(value).append(LINE_FEED);
writer.flush();
}
/**
* Adds a upload file section to the request
* @param fieldName name attribute in <input type="file" name="..." />
* @param uploadFile a File to be uploaded
* @throws IOException
*/
public void addFilePart(String fieldName, File uploadFile)
throws IOException {
String fileName = uploadFile.getName();
writer.append("--" + boundary).append(LINE_FEED);
writer.append(
"Content-Disposition: form-data; name=\"" + fieldName
+ "\"; filename=\"" + fileName + "\"")
.append(LINE_FEED);
writer.append(
"Content-Type: "
+ URLConnection.guessContentTypeFromName(fileName))
.append(LINE_FEED);
writer.append("Content-Transfer-Encoding: binary").append(LINE_FEED);
writer.append(LINE_FEED);
writer.flush();
FileInputStream inputStream = new FileInputStream(uploadFile);
byte[] buffer = new byte[4096];
int bytesRead = -1;
while ((bytesRead = inputStream.read(buffer)) != -1) {
outputStream.write(buffer, 0, bytesRead);
}
outputStream.flush();
inputStream.close();
writer.append(LINE_FEED);
writer.flush();
}
/**
* Completes the request and receives response from the server.
* @return a list of Strings as response in case the server returned
* status OK, otherwise an exception is thrown.
* @throws IOException
*/
public List<String> finish() throws IOException {
List<String> response = new ArrayList<String>();
writer.append(LINE_FEED).flush();
writer.append("--" + boundary + "--").append(LINE_FEED);
writer.close();
// checks server's status code first
int status = httpConn.getResponseCode();
if (status == HttpURLConnection.HTTP_OK) {
BufferedReader reader = new BufferedReader(new InputStreamReader(
httpConn.getInputStream()));
String line = null;
while ((line = reader.readLine()) != null) {
response.add(line);
}
reader.close();
httpConn.disconnect();
} else {
throw new IOException("Server returned non-OK status: " + status);
}
return response;
}
}
//---------------------------------------------------------
package net.codejava.networking;
import java.io.File;
import java.io.IOException;
import java.util.List;
/**
* This program demonstrates a usage of the MultipartUtility class.
* @author www.codejava.net
*
*/
public class MultipartFileUploader {
public static void main(String[] args) {
String charset = "UTF-8";
File uploadFile1 = new File("e:/Test/PIC1.JPG");
File uploadFile2 = new File("e:/Test/PIC2.JPG");
String requestURL = "http://localhost:8080/FileUploadSpringMVC/uploadFile.do";
try {
MultipartUtility multipart = new MultipartUtility(requestURL, charset);
multipart.addFormField("description", "Cool pix");
multipart.addFilePart("fileUpload", uploadFile1);
multipart.addFilePart("fileUpload", uploadFile2);
List<String> response = multipart.finish();
System.out.println("SERVER REPLIED:");
for (String line : response) {
System.out.println(line);
}
} catch (IOException ex) {
System.out.println("ERROR: " + ex.getMessage());
ex.printStackTrace();
}
}
}