使用JavaWeb实现文件的上传和下载

    
      commons-fileupload
      commons-fileupload
      1.3.3
    
    
    
      javax.servlet
      javax.servlet-api
      4.0.1
    
    
    
      javax.servlet.jsp
      javax.servlet.jsp-api
      2.3.3
      provided
    
    
    
      javax.servlet
      jstl
      1.2
    
    
    
      taglibs
      standard
      1.1.2
    

package com.lenovo.servlet;


import com.sun.org.apache.xml.internal.res.XMLErrorResources_tr;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.ProgressListener;
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.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
import java.util.UUID;

public class FileServlet extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //判断上传的文件是普通表非还是带文件的表单
        if (!ServletFileUpload.isMultipartContent(request)) {
            return; //终止方法运行说明这是一个普远的表单，直接返回
        }
        //创建上:传文件的保存路径，建议在WEB-INF路径下，安全，用户无法直接访问上传的文件;
        String uploadPath = this.getServletContext().getRealPath("/WEB-INF/upload");
        File uploadFile = new File(uploadPath);
        if (!uploadFile.exists()) {
            uploadFile.mkdir(); //创建这个目录
        }
        //级存，临时文件
        //临时路径，假如文件超过J预期的大小，我们就把他放到一一个临时文件中，过几天自动删除，或者提醒用户转存为承久
        String tmpPath = this.getServletContext().getRealPath("/WEB-INF/tmp");
        File file = new File(tmpPath);
        if (!file.exists()) {
            file.mkdir(); //创建这个临时目录
        }
        //处理上传的文件，一般 都需要通过流来获取，我们可以使request. getInputstream(),原生态的文件上传流获取，十分麻烦
        //但是我们都建议使用Apache的文件上:传组件米实现，common-fileupload, 它需要依赖于commons-io组件:
        /*
        ServletFileUpload负责处理上传的文件数据并将表单中每个输入项封装成- - 个FileItem对象。
        在使用ServletFileUpload对象解析请求时需要DiskFileItemFactory对象。
        所以，我们需要在进行解析工作前构造好DiskFileItemFactory对象。
        通过ServletFileUpload对象的构造方法或setFileItemFactory()方法设置ServletFileUpload对象的fileItemFactory属性。
        */
        try {
            //1.创建DiskFileItemFactory对象，处理文件上传路径或者大小限制的;
            DiskFileItemFactory factory = getDiskFileItemFactory(file);
            //2.获取ServletFileUpload
            ServletFileUpload upload = getServletFileUpload(factory);
            //3.处理上传的文件

            String msg = uploadParseRequest(upload, request, uploadPath);
            //servlet请求转发消息
            request.setAttribute("msg", msg);
            request.getRequestDispatcher("info.jsp").forward(request, response);

        } catch (FileUploadException e) {
            e.printStackTrace();
        }
    }

    public static DiskFileItemFactory getDiskFileItemFactory(File file) {
        DiskFil服务器托管网eItemFactory factory = new DiskFileItemFactory();
        //通过这个工厂设置一个缓冲区，当上传的文件大于这个缓冲区的时候，将他放到临时文件中;
        factory.setSizeThreshold(1024 * 1024); //缓存区大小为1M
        factory.setRepository(file);//临时目录的保存目录，需要一个File
        return factory;
    }

    public static ServletFileUpload getServletFileUpload(DiskFileItemFactory factory) {
        ServletFileUpload upload = new ServletFileUpload(factory);
        //监听文件上传进度;
        upload.setProgressListener(new ProgressListener() {
            @Override
            //pBytesRead:已经读取到的文件大小
            //pContentlength :文件大小
            public void update(long pBytesRead, long pContentLength, int pItems) {
                System.out.println("总大小:" + pContentLength + "已上传:" + pBytesRead);
            }
        });
        //处理乱码问题
        upload.setHeaderEncoding("UTF-8");
        //设置单个文件的最大值
        upload.setFileSizeMax(1024 * 1024 * 10);
        //设置总共能够上传文件的大小
        //1024=1kb*1024=1M*10=10M
        upload.setSizeMax(1024 * 1024 * 10);
        return upload;
    }

    public static String uploadParseRequest(ServletFileUpload upload, HttpServletRequest request, String uploadPath)
            throws FileUploadException, IOException {
        String msg = "";
        //3.把前端请求解析，封装成一个FileItem对象
        List fileItems = upload.parseRequest(request);
        for (FileItem fileItem : fileItems) {
            if (fileItem.isFormField()) { //判断上传的文件是普通的表单还是带文件的表单
                //getFieldName指的是前端表单控件的name;
                String name = fileItem.getFieldName();
                String value = fileItem.getString("UTF-8"); //处理乱码
                System.out.println(name + ":" + value);
            } else { //判断它是上传的文件
                /*====================处理文件========================*/
                //拿到文件名字
                String uploadFileName = fileItem.getName();
                System.out.println("上传的文件名: " + uploadFileName);
                if (uploadFileName.trim().equals("") || uploadFileName == null) {
                    continue;
                }
                //获得上传的文件名/images/girl/paojie. png
                String fileName = uploadFileName.substring(uploadFileName.lastIndexOf("/") + 1);
                //获得文件的后缀名
                String fileExtName = uploadFileName.substring(uploadFileName.lastIndexOf(".") + 1);
                /*
                如果文件后缀名fileExtName 不是我们所需要的
                就直接return,不处理，告诉用户文件类型不对。
                */
                System.out.println("文件信息[件名: " + fileName + "---文件类型" + fileExtName + "]");
                //可以使用UUID (唯一识别的通用码)，保证文件名唯一;
                //UUID. randomUUID()，随机生一个唯一识别的通 用码;
                String uuidPath = UUID.randomUUID().toString();
                /*==================处理文件完-=======================*/
                //存到哪? uploadPath
                //文件真实存在的路径realPath
                String realPath = uploadPath + "/" + uuidPath;
                //给每个文件创建一个对应的文件夹
                File realPathFile = new File(realPath);
                if (!realPathFile.exists()) {
      服务器托管网              realPathFile.mkdir();
                }
                /*====================存放地址完毕-========================*/
                //获得文件上传的流
                InputStream inputStream = fileItem.getInputStream();
                //创建一个文件输出流
                //realPath =真实的文件夹;
                //差了一个文件;加上输出文件的名字+"/"+uuidFileName
                FileOutputStream fos = new FileOutputStream(realPath + "/" + fileName);
                //创建一个缓冲区
                byte[] buffer = new byte[1024 * 1024];
                //判断是否读取完毕
                int len = 0;
                //如果大于0说明还存在数据;
                while ((len = inputStream.read(buffer)) > 0) {
                    fos.write(buffer, 0, len);
                }
                //关闭流
                fos.close();
                inputStream.close();
                msg = "文件上传成功!";
                fileItem.delete(); //上传成功，清除临时文件
                /*====================文件传输完==========================*/
            }
        }
        return msg;
    }
}

    
        FileServlet
        com.lenovo.servlet.FileServlet
    
    
        FileServlet
        /upload.do
    

    


${msg}

public class FileServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 1.要获取下载文件的路径
        String realPath = "D:ProjectIdeaProjectjavaweb-01-servletresponsesrcmainresource西贝.jpg";
        System.out.println("下载文件的路径: " + realPath);
        // 2.下载的文件名是啥?
        String fileName = realPath.substring(realPath.lastIndexOf("") + 1);
        // 3.设置想办法让浏览器能够支持(Content -Disposition)下载我们需要的东西，中文文件名URLEncoder . encode编码，否则有可能乱码
        resp.setHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(fileName, "UTF-8"));
        // 4.获取下载文件的输入流
        FileInputStream in = new FileInputStream(realPath);
        // 5.创建缓冲区
        int len = 0;
        byte[] buffer = new byte[1024];
        // 6.获取0utputStream对象
        ServletOutputStream out = resp.getOutputStream();
        // 7.将FileOutputStream流 写入到buffer缓冲区,使用Outputstream将缓冲区中的数据输出到客户端!
        while ((len = in.read(buffer)) > 0) {
            out.write(buffer, 0, len);
        }
        in.close();
        out.close();

    }

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