摘要：一添加项目依赖二上传上传文件存储目录上传配置上传文件最大值检测是否为多媒体上传如果不是则停止表单必须包含配置上传参数设置最大文件上传值中文处理构造临时路径来存储上传的文件这个路径相对当前应用的目录如果目录不存在则创建解析请求的内容

dependencies {
    compile group: "javax.servlet", name: "javax.servlet-api", version: "3.1.0"
    compile group: "commons-fileupload", name: "commons-fileupload", version: "1.3.3"
    compile group: "javax.servlet", name: "jstl", version: "1.2"
}

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.io.IOException;
import java.io.PrintWriter;
import java.util.*;

public class UploadServlet extends HttpServlet {
    // 上传文件存储目录
    private static final String UPLOAD_DIRECTORY = "upload";

    // 上传配置 上传文件最大值
    private static final int MAX_FILE_SIZE = 1024 * 1024 * 40; // 40MB


    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 检测是否为多媒体上传
        if (!ServletFileUpload.isMultipartContent(request)) {
            // 如果不是则停止
            PrintWriter writer = response.getWriter();
            writer.println("Error: 表单必须包含 enctype=multipart/form-data");
            writer.flush();
            return;
        }

        // 配置上传参数
        DiskFileItemFactory factory = new DiskFileItemFactory();
        ServletFileUpload upload = new ServletFileUpload(factory);
        // 设置最大文件上传值
        upload.setFileSizeMax(MAX_FILE_SIZE);
        // 中文处理
        upload.setHeaderEncoding("UTF-8");
        // 构造临时路径来存储上传的文件
        // 这个路径相对当前应用的目录
        String uploadPath = request.getServletContext().getRealPath("./") + File.separator + UPLOAD_DIRECTORY;

        // 如果目录不存在则创建
        File uploadDir = new File(uploadPath);
        if (!uploadDir.exists()) {
            uploadDir.mkdir();
        }

        List> data = new ArrayList<>();

        try {
            // 解析请求的内容提取文件数据
            List formItems = upload.parseRequest(request);
            if (formItems != null && formItems.size() > 0) {
                // 迭代表单数据
                for (FileItem item : formItems) {
                    // 处理不在表单中的字段
                    if (!item.isFormField()) {
                        String fileName = item.getName();
                        String filePath = uploadPath + File.separator + UUID.randomUUID() + fileName;
                        File storeFile = new File(filePath);
                        // 在控制台输出文件的上传路径
                        System.out.println(filePath);
                        // 保存文件到硬盘
                        item.write(storeFile);
                        data.add(new HashMap() {{
                            put("name", fileName);
                            put("path", filePath);
                        }});
                    }
                }
            }
            request.getSession().setAttribute("list", data);
            request.setAttribute("message", "文件上传成功!");
        } catch (Exception ex) {
            request.setAttribute("message", "错误信息: " + ex.getMessage());
        }
        // 跳转到 message.jsp
        request.getServletContext().getRequestDispatcher("/message.jsp").forward(request, response);
    }
}

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.net.URLEncoder;

public class DownloadServlet extends HttpServlet {

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


    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        String path = request.getParameter("path");
        //处理请求
        //读取要下载的文件
        File f = new File(path);
        if (f.exists()) {
            FileInputStream fis = new FileInputStream(f);
            String filename = URLEncoder.encode(f.getName(), "utf-8"); //解决中文文件名下载后乱码的问题
            byte[] b = new byte[fis.available()];
            fis.read(b);
            response.setCharacterEncoding("utf-8");
            response.setHeader("Content-Disposition", "attachment; filename=" + filename + "");
            //获取响应报文输出流对象
            ServletOutputStream out = response.getOutputStream();
            //输出
            out.write(b);
            out.flush();
            out.close();
        }

    }
}

    
        uploadServlet
        stu.servlet.UploadServlet
    
    
        downloadServlet
        stu.servlet.DownloadServlet
    
    
        uploadServlet
        /uploadServlet
    
    
        downloadServlet
        /downloadServlet
    

<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    


文件上传

    选择一个文件:
    
    


    

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>


    


${message}
文件列表

        

    

    

        
文件
        
下载
    
    

            
${item.name}
            
下载