为文件发送多个文件，我们必须使用enctype="multipart/form-data"。

如果要发送多个文件，在input标签中使用multiple="multiple":

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

对于Spring MVC

我设法有一个更简单的版本，用于获取表单输入，包括数据和图像。

<form action="/handleform" method="post" enctype="multipart/form-data">
    <input type="text" name="name" />
    <input type="text" name="age" />
    <input type="file" name="file" />
    <input type="submit" />
</form>

要处理的控制器

@Controller
public class FormController {
    @RequestMapping(value="/handleform",method= RequestMethod.POST)
    ModelAndView register(@RequestParam String name, @RequestParam int age, @RequestParam MultipartFile file)
            throws ServletException, IOException {

        System.out.println(name);
        System.out.println(age);
        if(!file.isEmpty()){
            byte[] bytes = file.getBytes();
            String filename = file.getOriginalFilename();
            BufferedOutputStream stream =new BufferedOutputStream(new FileOutputStream(new File("D:/" + filename)));
            stream.write(bytes);
            stream.flush();
            stream.close();
        }
        return new ModelAndView("index");
    }
}

如果您使用Geronimo及其嵌入式Tomcat，则会出现此问题的另一个来源。在本例中，经过多次测试Commons IO和Commons -fileupload后，问题产生于处理Commons -xxx JAR文件的父类加载器。这种情况必须加以防止。坠机通常发生在:

fileItems = uploader.parseRequest(request);

请注意，fileItems的List类型已经随着common -fileupload的当前版本而改变，具体为List<FileItem>，而不是以前的版本，它是一般的List。

I added the source code for commons-fileupload and Commons IO into my Eclipse project to trace the actual error and finally got some insight. First, the exception thrown is of type Throwable not the stated FileIOException nor even Exception (these will not be trapped). Second, the error message is obfuscatory in that it stated class not found because axis2 could not find commons-io. Axis2 is not used in my project at all, but it exists as a folder in the Geronimo repository subdirectory as part of standard installation.

最后，我找到了一个地方，提出了一个有效的解决方案，成功地解决了我的问题。您必须将JAR文件隐藏在部署计划中的父加载器中。它被放入geronimo-web.xml文件中，我的完整文件如下所示。

粘贴自http://osdir.com/ml/user-geronimo-apache/2011-03/msg00026.html:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<web:web-app xmlns:app="http://geronimo.apache.org/xml/ns/j2ee/application-2.0" xmlns:client="http://geronimo.apache.org/xml/ns/j2ee/application-client-2.0" xmlns:conn="http://geronimo.apache.org/xml/ns/j2ee/connector-1.2" xmlns:dep="http://geronimo.apache.org/xml/ns/deployment-1.2" xmlns:ejb="http://openejb.apache.org/xml/ns/openejb-jar-2.2" xmlns:log="http://geronimo.apache.org/xml/ns/loginconfig-2.0" xmlns:name="http://geronimo.apache.org/xml/ns/naming-1.2" xmlns:pers="http://java.sun.com/xml/ns/persistence" xmlns:pkgen="http://openejb.apache.org/xml/ns/pkgen-2.1" xmlns:sec="http://geronimo.apache.org/xml/ns/security-2.0" xmlns:web="http://geronimo.apache.org/xml/ns/j2ee/web-2.0.1">
    <dep:environment>
        <dep:moduleId>
            <dep:groupId>DataStar</dep:groupId>
            <dep:artifactId>DataStar</dep:artifactId>
            <dep:version>1.0</dep:version>
            <dep:type>car</dep:type>
        </dep:moduleId>

        <!-- Don't load commons-io or fileupload from parent classloaders -->
        <dep:hidden-classes>
            <dep:filter>org.apache.commons.io</dep:filter>
            <dep:filter>org.apache.commons.fileupload</dep:filter>
        </dep:hidden-classes>
        <dep:inverse-classloading/>

    </dep:environment>
    <web:context-root>/DataStar</web:context-root>
</web:web-app>

您可以使用JSP /servlet上传文件。

<form action="UploadFileServlet" method="post">
    <input type="text" name="description" />
    <input type="file" name="file" />
    <input type="submit" />
</form>

另一方面，在服务器端，使用以下代码。

package com.abc..servlet;

import java.io.File;
---------
--------


/**
 * Servlet implementation class UploadFileServlet
 */
public class UploadFileServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public UploadFileServlet() {
        super();
        // TODO Auto-generated constructor stub
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        response.sendRedirect("../jsp/ErrorPage.jsp");
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub

        PrintWriter out = response.getWriter();
        HttpSession httpSession = request.getSession();
        String filePathUpload = (String) httpSession.getAttribute("path") != null ? httpSession.getAttribute("path").toString() : "" ;

        String path1 = filePathUpload;
        String filename = null;
        File path = null;
        FileItem item = null;


        boolean isMultipart = ServletFileUpload.isMultipartContent(request);

        if (isMultipart) {
            FileItemFactory factory = new DiskFileItemFactory();
            ServletFileUpload upload = new ServletFileUpload(factory);
            String FieldName = "";
            try {
                List items = upload.parseRequest(request);
                Iterator iterator = items.iterator();
                while (iterator.hasNext()) {
                     item = (FileItem) iterator.next();

                        if (fieldname.equals("description")) {
                            description = item.getString();
                        }
                    }
                    if (!item.isFormField()) {
                        filename = item.getName();
                        path = new File(path1 + File.separator);
                        if (!path.exists()) {
                            boolean status = path.mkdirs();
                        }
                        /* Start of code fro privilege */

                        File uploadedFile = new File(path + Filename);  // for copy file
                        item.write(uploadedFile);
                        }
                    } else {
                        f1 = item.getName();
                    }

                } // END OF WHILE
                response.sendRedirect("welcome.jsp");
            } catch (FileUploadException e) {
                e.printStackTrace();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

HTML页面

<html>
    <head>
        <title>File Uploading Form</title>
    </head>

    <body>
        <h3>File Upload:</h3>
        Select a file to upload: <br />
        <form action="UploadServlet" method="post"
              enctype="multipart/form-data">

            <input type="file" name="file" size="50" />
            <br />
            <input type="submit" value="Upload File" />
        </form>
    </body>
</html>

Servlet文件

// Import required java libraries
import java.io.*;
import java.util.*;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.io.output.*;

public class UploadServlet extends HttpServlet {

    private boolean isMultipart;
    private String filePath;
    private int maxFileSize = 50 * 1024;
    private int maxMemSize = 4 * 1024;
    private File file;

    public void init() {
        // Get the file location where it would be stored.
        filePath =
               getServletContext().getInitParameter("file-upload");
    }

    public void doPost(HttpServletRequest request,
                       HttpServletResponse response)
               throws ServletException, java.io.IOException {

        // Check that we have a file upload request
        isMultipart = ServletFileUpload.isMultipartContent(request);
        response.setContentType("text/html");
        java.io.PrintWriter out = response.getWriter();
        if (!isMultipart) {
            out.println("<html>");
            out.println("<head>");
            out.println("<title>Servlet upload</title>");
            out.println("</head>");
            out.println("<body>");
            out.println("<p>No file uploaded</p>");
            out.println("</body>");
            out.println("</html>");
            return;
        }

        DiskFileItemFactory factory = new DiskFileItemFactory();
        // Maximum size that will be stored in memory
        factory.setSizeThreshold(maxMemSize);
        // Location to save data that is larger than maxMemSize.
        factory.setRepository(new File("c:\\temp"));

        // Create a new file upload handler
        ServletFileUpload upload = new ServletFileUpload(factory);
        // maximum file size to be uploaded.
        upload.setSizeMax(maxFileSize);

        try {
            // Parse the request to get file items.
            List fileItems = upload.parseRequest(request);

            // Process the uploaded file items
            Iterator i = fileItems.iterator();

            out.println("<html>");
            out.println("<head>");
            out.println("<title>Servlet upload</title>");
            out.println("</head>");
            out.println("<body>");
            while (i.hasNext())
            {
                FileItem fi = (FileItem)i.next();
                if (!fi.isFormField())
                {
                     // Get the uploaded file parameters
                     String fieldName = fi.getFieldName();
                     String fileName = fi.getName();
                     String contentType = fi.getContentType();
                     boolean isInMemory = fi.isInMemory();
                     long sizeInBytes = fi.getSize();

                     // Write the file
                     if (fileName.lastIndexOf("\\") >= 0) {
                         file = new File(filePath +
                         fileName.substring(fileName.lastIndexOf("\\")));
                     }
                     else {
                         file = new File(filePath +
                         fileName.substring(fileName.lastIndexOf("\\") + 1));
                     }
                     fi.write(file);
                     out.println("Uploaded Filename: " + fileName + "<br>");
                }
            }
            out.println("</body>");
            out.println("</html>");
        }
        catch(Exception ex) {
            System.out.println(ex);
        }
    }

    public void doGet(HttpServletRequest request,
                        HttpServletResponse response)
            throws ServletException, java.io.IOException {

        throw new ServletException("GET method used with " +
                 getClass().getName() + ": POST method required.");
    }
}

文件web . xml

编译上面的servlet UploadServlet并在web.xml文件中创建所需的条目，如下所示。

<servlet>
   <servlet-name>UploadServlet</servlet-name>
   <servlet-class>UploadServlet</servlet-class>
</servlet>

<servlet-mapping>
   <servlet-name>UploadServlet</servlet-name>
   <url-pattern>/UploadServlet</url-pattern>
</servlet-mapping>

下面是一个使用apache common -fileupload的例子:

// apache commons-fileupload to handle file upload
DiskFileItemFactory factory = new DiskFileItemFactory();
factory.setRepository(new File(DataSources.TORRENTS_DIR()));
ServletFileUpload fileUpload = new ServletFileUpload(factory);

List<FileItem> items = fileUpload.parseRequest(req.raw());
FileItem item = items.stream()
  .filter(e ->
  "the_upload_name".equals(e.getFieldName()))
  .findFirst().get();
String fileName = item.getName();

item.write(new File(dir, fileName));
log.info(fileName);