Java - file upload problem [duplicate]

This question already has answers here: How can I upload files to a server using JSP/Servlet? (14 answers) Closed 6 years ago.

Servlet

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.Iterator;
import java.util.List;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.*;

public class Apply extends HttpServlet
{
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
                            throws ServletException, IOException
    {
        InputStreamReader input = new InputStreamReader(request.getInputStream());
        BufferedReader buffer = new BufferedReader(input);
        String line="";
        line=buffer.readLine();

        开发者_运维知识库System.out.println("Multipart data " + line );

        boolean isMultipart = ServletFileUpload.isMultipartContent(request);
        if(isMultipart)
        {
            // upload file
        }
        else
        {
            // failed, no input
        }
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response)
                            throws ServletException, IOException
    {
        doPost(request, response);
    }
}

JSP.

        <form enctype="multipart/form-data" method="post" action="apply">
            <fieldset>
                <br/>
                <legend>Upload</legend>
                <br/>
                <label>Select file to upload</label>
                <input type="file" name="file" /><br />
                <br/>
                <a href="apply" class="jUiButton">Submit</a>
            </fieldset>
        </form>     
        <script>$(".jUiButton").button()</script>

The boolean and input always validates as false/null and I can't figure why. Following this guide: http://sacharya.com/file-upload/

in the web-inf/lib - we have commons-fileupload-1.2.2.jar and commons-io-2.0.1.jar.

Any ideas?

---

You're not actually submitting the form. You're navigating to the page with a GET request.

Replace your "Submit" anchor with a submit button:

<button type="submit" class="jUiButton">Submit</button>

You could keep the <a> but then you would have to use JavaScript to submit the form manually.

---

You should not read the HttpServletRequest#getInputStream() beforehand. It can be read only once. The Commons FileUpload cannot read it anymore if you have read it yourself beforehand. Get rid of all those lines in your servlet until ServletFileUpload#isMultipartContent() line.

---

The guide you are following is out of date (2008). If this is a new project you might want to start with an annotation based approach. This guide might be better to follow (2010). A file upload controller would then look like:

@Controller
public class FileUploadContoller {   
    @RequestMapping(value = "/fileupload", method = RequestMethod.POST)
    @ResponseStatus(HttpStatus.OK)
    @ResponseBody
    public String ingest(@RequestParam("file") final MultipartFile file) throws Exception {
        if (file.isEmpty()) {
            System.out.println("empty");
        } else {
            System.out.println("not empty");
        }

        // do something with file.getBytes()

        return("ok");
    }
}

This is only the controller and you will need to add the appropriate Spring configuration. I could help further if you want to go down this route.