jsp文件上传控件

<dependency>
    <groupId>commons-fileupload</groupId>
    <artifactId>commons-fileupload</artifactId>
    <version>1.4</version>
</dependency>
<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.8.0</version>
</dependency>

<form action="upload" method="post" enctype="multipart/form-data">
    <input type="file" name="file" />
    <input type="submit" value="Upload" />
</form>

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.util.List;

public class FileUploadServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    private static final String UPLOAD_DIRECTORY = "uploads";
    private static final int MEMORY_THRESHOLD = 1024 * 1024 * 3;  // 3MB
    private static final int MAX_FILE_SIZE = 1024 * 1024 * 40; // 40MB
    private static final int MAX_REQUEST_SIZE = 1024 * 1024 * 50; // 50MB

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        if (!ServletFileUpload.isMultipartContent(request)) {
            response.getWriter().println("Error: Form must have enctype=multipart/form-data.");
            return;
        }

        DiskFileItemFactory factory = new DiskFileItemFactory();
        factory.setSizeThreshold(MEMORY_THRESHOLD);
        factory.setRepository(new File(System.getProperty("java.io.tmpdir")));

        ServletFileUpload upload = new ServletFileUpload(factory);
        upload.setFileSizeMax(MAX_FILE_SIZE);
        upload.setSizeMax(MAX_REQUEST_SIZE);

        String uploadPath = getServletContext().getRealPath("") + File.separator + UPLOAD_DIRECTORY;
        File uploadDir = new File(uploadPath);
        if (!uploadDir.exists()) uploadDir.mkdir();

        try {
            List<FileItem> formItems = upload.parseRequest(request);
            if (formItems != null && formItems.size() > 0) {
                for (FileItem item : formItems) {
                    if (!item.isFormField()) {
                        String fileName = new File(item.getName()).getName();
                        String filePath = uploadPath + File.separator + fileName;
                        File storeFile = new File(filePath);
                        item.write(storeFile);
                        response.getWriter().println("File " + fileName + " has uploaded successfully!");
                    }
                }
            }
        } catch (Exception ex) {
            response.getWriter().println("There was an error: " + ex.getMessage());
        }
    }
}