How could I upload a large file in chunks using Java?

Question

I need to upload a large file in chunks using Java.

Is there any sample code I can refer to?

Answer 1

*It can be done using plupload. Here is sample. My index.html is as under:-

    
    
    
    
    
    
    
    
    
    
    

    

        Select file 
        Upload
        

    
    

    

    
    
    

My java backend code(Servlet) is as under:-

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.fileupload.FileItemIterator;
import org.apache.commons.fileupload.FileItemStream;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.fileupload.util.Streams;
public class UploadAction extends HttpServlet {
    private static final long serialVersionUID = 3447685998419256747L;
    private static final String RESP_SUCCESS = "{\"jsonrpc\" : \"2.0\", \"result\" : \"success\", \"id\" : \"id\"}";
    private static final String RESP_ERROR = "{\"jsonrpc\" : \"2.0\", \"error\" : {\"code\": 101, \"message\": \"Failed to open input stream.\"}, \"id\" : \"id\"}";
    public static final String JSON = "application/json";
    public static final int BUF_SIZE = 2 * 1024;
    public static final String FileDir = "/home/asjha/uploads/";

    private int chunk;
    private int chunks;
    private String name;
    private String user;
    private String time;
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String responseString = RESP_SUCCESS;
        boolean isMultipart = ServletFileUpload.isMultipartContent(req);

        if(isMultipart){
            ServletFileUpload upload = new ServletFileUpload();
            try {
                FileItemIterator iter = upload.getItemIterator(req);
                while (iter.hasNext()) {
                    FileItemStream item = iter.next();
                    InputStream input = item.openStream();
                    // Handle a form field.
                    if(item.isFormField()){
                        String fileName = item.getFieldName();
                        String value = Streams.asString(input);
                        if("name".equals(fileName)){
                            this.name = value;
                        }else if("chunks".equals(fileName)){
                            this.chunks = Integer.parseInt(value);
                        }else if("chunk".equals(fileName)){
                            this.chunk = Integer.parseInt(value);
                        }else if("user".equals(fileName)){
                            this.user = value;
                        }else if("time".equals(fileName)){
                            this.time = value;
                        }
                    }

                    // Handle a multi-part MIME encoded file.
                    else {
                        File dstFile = new File(FileDir);
                        if (!dstFile.exists()){
                            dstFile.mkdirs();
                        }

                        File dst = new File(dstFile.getPath()+ "/" + this.name);

                        saveUploadFile(input, dst);
                    }
                }
            }
            catch (Exception e) {
                responseString = RESP_ERROR;
                e.printStackTrace();
            }
        }

        // Not a multi-part MIME request.
        else {
            responseString = RESP_ERROR;
        }

        if(this.chunk == this.chunks - 1){
            System.out.println("name"+this.name);
        }
        resp.setContentType(JSON);
        byte[] responseBytes = responseString.getBytes();
        resp.setContentLength(responseBytes.length);
        ServletOutputStream output = resp.getOutputStream();
        output.write(responseBytes);
        output.flush();
    }
    private void saveUploadFile(InputStream input, File dst) throws IOException {
        OutputStream out = null;
        try {
            if (dst.exists()) {
                out = new BufferedOutputStream(new FileOutputStream(dst, true),
                        BUF_SIZE);
            } else {
                out = new BufferedOutputStream(new FileOutputStream(dst),
                        BUF_SIZE);
            }
            byte[] buffer = new byte[BUF_SIZE];
            int len = 0;
            while ((len = input.read(buffer)) > 0) {
                out.write(buffer, 0, len);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (null != input) {
                try {
                    input.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (null != out) {
                try {
                    out.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

Please refer to plupload for details and on github you can see sample projects by jakobadam and rocky.

Please let me know if multiple file upload is required. Using plupload we can upload any number of files of any sizes. This sample is for single file upload of very large size. dont forget to include plupload.full.min.js. Hope this helps*emphasized text**