如何用java从多部分数据格式创建接收代码

我正在尝试使用java将url中的文件作为多部分表单数据发布，并尝试接收存储在特定文件夹中的文件。当我收到一个文件时，它显示空值。因此，我需要如何在java中接收文件。请给出一些有价值的例子，谢谢。我需要在main方法中提供清晰的信息

package com.jobsonthego.json;
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;

import org.apache.commons.io.FileUtils;

import com.jobsonthego.common.ApplicationAction;

@SuppressWarnings("serial")
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;
     // creates a unique boundary based on time stamp
    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.setUseCaches(false);
        httpConn.setDoOutput(true); // indicates POST method
        httpConn.setDoInput(true);
        httpConn.setRequestProperty("Content-Type",
                "multipart/form-data; boundary=" + boundary);
        httpConn.setRequestProperty("User-Agent", "CodeJava Agent");
        httpConn.setRequestProperty("Test", "Bonjour");
        outputStream = httpConn.getOutputStream();
        writer = new PrintWriter(new OutputStreamWriter(outputStream, charset),
                true);
    }
    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);
        System.out.println("bytesRead"+inputStream);
        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();    
    }
    public void addHeaderField(String name, String value) {
        writer.append(name + ": " + value).append(LINE_FEED);
        writer.flush();
    }
    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();
        System.out.println("status"+status);
        if (status == HttpURLConnection.HTTP_OK) {
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    httpConn.getInputStream()));

            String line = null;
            while ((line = reader.readLine()) != null) {
                   System.out.println("line"+reader);
                response.add(line);
            }

            reader.close();
            httpConn.disconnect();
            System.out.println("finish"+response);
        } else {
            throw new IOException("Server returned non-OK status: " + status);
        }
        return response;
    }
      public static void main(String[] args) {
            String charset = "UTF-8";
            File uploadFile1 = new File("C:/Users/user/Music/22.jpg");
            File uploadFile2 = new File("C:/Users/user/Music/22.jpg");
            String requestURL = "http://localhost/userinfo/fileUpload";
            try {
                MultipartUtility multipart = new MultipartUtility(requestURL, charset);
                multipart.addHeaderField("User-Agent", "CodeJava");
                multipart.addHeaderField("Test-Header", "Header-Value");
                multipart.addFilePart("postImage", uploadFile1);
                multipart.addFilePart("postImage", uploadFile2);
                List<String> response = multipart.finish();
                System.out.println("response"+response);
                System.out.println("SERVER REPLIED:");
                for (String line : response) {
                    System.out.println(line);
                }
            } catch (IOException ex) {
                System.err.println(ex);
            }
        }

}

---

以下代码需要javax.mail依赖项

例如，这是您的主代码

if (mimeMessage.getContentType().contains("multipart")) {
    Multipart multiPart = (Multipart) mimeMessage.getContent();
    messageContent = (String)messageContent;
    messageContent = "";
for (int partCount = 0; partCount < multiPart.getCount(); partCount++) {
    MimeBodyPart part = (MimeBodyPart) multiPart
            .getBodyPart(partCount);
    if (!Part.ATTACHMENT
            .equalsIgnoreCase(part.getDisposition())) {
        // this part is the message content
        content = getText(part,embededImgMap);
    }
}
}

使用以下方法获取多部分内容

private String getText(Part p, Map<String, String> embededImgMap) throws MessagingException, IOException {
    if(p.isMimeType("image/*")){

        InputStream inStream = p.getInputStream();
        String contentHeader = p.getHeader("Content-ID")[0];
        if(contentHeader !=null){
            contentHeader = contentHeader.replaceAll("<", "").replaceAll(">", "");
        }
        InlineImage inlineImg = new InlineImage();
        inlineImg.setCidKey(contentHeader);
        inlineImg.setImgData(IOUtils.toByteArray(inStream));
        new MessageStoreDAO().storeInlineImg(inlineImg );
        embededImgMap.put(contentHeader,p.getFileName());

    }
    if (p.isMimeType("text/*")) {
        String s = "";
        Object objContent = p.getContent();
        if(objContent instanceof String){
            if(p.isMimeType("text/html")){
                s = (String) objContent;
            }

        }else if(objContent instanceof BASE64DecoderStream){
            Logger.info("GetBase64 encoding");
        }
        return s;
    }

    if (p.isMimeType("multipart/alternative")) {
        // prefer html text over plain text
        Multipart mp = (Multipart) p.getContent();
        String text = null;
        for (int i = 0; i < mp.getCount(); i++) {
            Part bp = mp.getBodyPart(i);
            if (bp.isMimeType("text/plain")) {
                String s = getText(bp,embededImgMap);
                if (s != null){
                    return s;
                }
            } else if (bp.isMimeType("text/html")) {
                String s = getText(bp,embededImgMap);
                if (s != null){
                    return s;
                }
            } else {
                return getText(bp,embededImgMap);
            }
        }
        return text;
    } else if (p.isMimeType("multipart/*")) {
        Multipart mp = (Multipart) p.getContent();
        for (int i = 0; i < mp.getCount(); i++) {
            String s = getText(mp.getBodyPart(i),embededImgMap);
            if (s != null){
                return s;
            }
        }
    }else if (p.isMimeType("multipart/related")) {
        Multipart mp = (Multipart) p.getContent();
        for (int i = 0; i < mp.getCount(); i++) {
            String s = getText(mp.getBodyPart(i),embededImgMap);
            if (s != null){
                return s;
            }
        }
    }

    return "";
}