servlet上傳下載

xuweijian 發(fā)布于2019-08-16 12:38 / 2459人閱讀

摘要：一添加項(xiàng)目依賴二上傳上傳文件存儲(chǔ)目錄上傳配置上傳文件最大值檢測(cè)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(shè)置最大文件上傳值中文處理構(gòu)造臨時(shí)路徑來(lái)存儲(chǔ)上傳的文件這個(gè)路徑相對(duì)當(dāng)前應(yīng)用的目錄如果目錄不存在則創(chuàng)建解析請(qǐng)求的內(nèi)容

一、添加項(xiàng)目依賴(gradle)

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"
}

二、上傳servlet

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(chǔ)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(cè)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(shè)置最大文件上傳值
        upload.setFileSizeMax(MAX_FILE_SIZE);
        // 中文處理
        upload.setHeaderEncoding("UTF-8");
        // 構(gòu)造臨時(shí)路徑來(lái)存儲(chǔ)上傳的文件
        // 這個(gè)路徑相對(duì)當(dāng)前應(yīng)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(qǐng)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(tái)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(cuò)誤信息: " + ex.getMessage());
        }
        // 跳轉(zhuǎn)到 message.jsp
        request.getServletContext().getRequestDispatcher("/message.jsp").forward(request, response);
    }
}

三、下載servlet

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(qǐng)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(yīng)報(bào)文輸出流對(duì)象
            ServletOutputStream out = response.getOutputStream();
            //輸出
            out.write(b);
            out.flush();
            out.close();
        }

    }
}

四、配置web.xml


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

五、上傳的jsp

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


    $Title$


文件上傳

    選擇一個(gè)文件:

六、下載的jsp

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


    Title


${message}
文件列表

        
    
    
        文件
        下載
    
    
            ${item.name}
            下載