摘要：一添加項目依賴二上傳上傳文件存儲目錄上傳配置上傳文件最大值檢測是否為多媒體上傳如果不是則停止表單必須包含配置上傳參數(shù)設置最大文件上傳值中文處理構造臨時路徑來存儲上傳的文件這個路徑相對當前應用的目錄如果目錄不存在則創(chuàng)建解析請求的內(nèi)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 {
    // 上傳文件存儲目錄
    private static final String UPLOAD_DIRECTORY = "upload";

    // 上傳配置 上傳文件最大值
    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 {
        // 檢測是否為多媒體上傳
        if (!ServletFileUpload.isMultipartContent(request)) {
            // 如果不是則停止
            PrintWriter writer = response.getWriter();
            writer.println("Error: 表單必須包含 enctype=multipart/form-data");
            writer.flush();
            return;
        }

        // 配置上傳參數(shù)
        DiskFileItemFactory factory = new DiskFileItemFactory();
        ServletFileUpload upload = new ServletFileUpload(factory);
        // 設置最大文件上傳值
        upload.setFileSizeMax(MAX_FILE_SIZE);
        // 中文處理
        upload.setHeaderEncoding("UTF-8");
        // 構造臨時路徑來存儲上傳的文件
        // 這個路徑相對當前應用的目錄
        String uploadPath = request.getServletContext().getRealPath("./") + File.separator + UPLOAD_DIRECTORY;

        // 如果目錄不存在則創(chuàng)建
        File uploadDir = new File(uploadPath);
        if (!uploadDir.exists()) {
            uploadDir.mkdir();
        }

        List> data = new ArrayList<>();

        try {
            // 解析請求的內(nèi)容提取文件數(shù)據(jù)
            List formItems = upload.parseRequest(request);
            if (formItems != null && formItems.size() > 0) {
                // 迭代表單數(shù)據(jù)
                for (FileItem item : formItems) {
                    // 處理不在表單中的字段
                    if (!item.isFormField()) {
                        String fileName = item.getName();
                        String filePath = uploadPath + File.separator + UUID.randomUUID() + fileName;
                        File storeFile = new File(filePath);
                        // 在控制臺輸出文件的上傳路徑
                        System.out.println(filePath);
                        // 保存文件到硬盤
                        item.write(storeFile);
                        data.add(new HashMap() {{
                            put("name", fileName);
                            put("path", filePath);
                        }});
                    }
                }
            }
            request.getSession().setAttribute("list", data);
            request.setAttribute("message", "文件上傳成功!");
        } catch (Exception ex) {
            request.setAttribute("message", "錯誤信息: " + ex.getMessage());
        }
        // 跳轉到 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");
        //處理請求
        //讀取要下載的文件
        File f = new File(path);
        if (f.exists()) {
            FileInputStream fis = new FileInputStream(f);
            String filename = URLEncoder.encode(f.getName(), "utf-8"); //解決中文文件名下載后亂碼的問題
            byte[] b = new byte[fis.available()];
            fis.read(b);
            response.setCharacterEncoding("utf-8");
            response.setHeader("Content-Disposition", "attachment; filename=" + filename + "");
            //獲取響應報文輸出流對象
            ServletOutputStream out = response.getOutputStream();
            //輸出
            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" %>


    


文件上傳

    選擇一個文件:
    
    


    

<%@ 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
        
下載
    
    

            
${item.name}
            
下載