文件上传与下载

上传：

Servlet2.5

<form action="${pageContext.request.contextPath }/uploadServlet" method="POST" enctype="multipart/form-data">
        姓名:<input type="text" name="name"/> <br>
        年龄:<input type="text" name="age"/> <br>
        照片:<input type="file" name="photo"/> <br>
        <input type="submit" value="注册"/>
</form>

package com.lijie.servlets;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.Iterator;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.ServletInputStream;
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;


public class UploadServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        
        /*ServletInputStream is = request.getInputStream();
        response.setContentType("text/html;charset=UTF-8");
        
        PrintWriter out = response.getWriter();
        int len = -1;
        byte[] buffer = new byte[1024];
        while((len = is.read(buffer))!=-1){
            String str = new String(buffer);
            out.println(str);
        }
        is.close();*/
        
        System.out.println("===========执行上传===========");
        //解析请求
        try {
            //判断请求类型
            boolean isMultipart = ServletFileUpload.isMultipartContent(request);
            if(!isMultipart){
                throw new RuntimeException("当前请求不支持文件上传!");
            }
            //创建FileItem工厂
            DiskFileItemFactory factory = new DiskFileItemFactory();
            //设置使用临时文件的边界值(大于该值，上传文件会保存在临时文件中，小于等于该值，写入内存。单位:字节)
            //本例设置为1M(1M=1024KB 1KB=1024B)
            factory.setSizeThreshold(1024 * 1024 * 1);
            //设置临时文件(上传完毕后要删除temp文件夹下的文件)
            File tempFile = new File(this.getServletContext().getRealPath("/temp"));
            factory.setRepository(tempFile);
            
            //创建文件上传核心组件
            ServletFileUpload upload = new ServletFileUpload(factory);
            //防止文件名乱码
            upload.setHeaderEncoding("UTF-8");
            //限制单次上传的文件大小边界值
            upload.setFileSizeMax(1024*1024*2);
            //限制多文件上传时的大小总和(这里是单文件，所有不起作用)
            upload.setSizeMax(1024*1024*5);
            //解析请求获取所有的Item
            List<FileItem> items = upload.parseRequest(request);
            //遍历Item
            Iterator<FileItem> iter = items.iterator();
            while (iter.hasNext()) {
                FileItem item = iter.next();
                if (item.isFormField()) {
                    //普通表单项
                    String fieldName = item.getFieldName();
                    String fieldValue = item.getString("UTF-8");
                    System.out.println(fieldName+" = "+fieldValue);
                } else {
                    //文件上传表单项
                    String fileName = item.getName();
                    //防止上传同名文件
                    fileName = System.currentTimeMillis() + fileName;
                    //输入流
                    InputStream is = item.getInputStream();
                    String path = this.getServletContext().getRealPath("/images");
                    
                    
                    //由于windows系统一个文件夹下最多有65535个文件
                    //所有对images文件夹下再进行分文件夹进行存储上传的文件
                    //1.按照yyyyMMdd的日期存放
                    /*Date now = new Date();
                    SimpleDateFormat format = new SimpleDateFormat("yyyyMMdd");
                    String nowTime = format.format(now);
                    path =  path + "/" + nowTime;
                    System.out.println("文件在服务器地址:" + path);
                    File dirFile = new File(path);
                    if(!dirFile.exists()){
                        dirFile.mkdir();
                    }*/
                    //2.按照年月日的格式分多级目录存放
                    Calendar now = Calendar.getInstance();
                    int year = now.get(Calendar.YEAR);
                    int month = now.get(Calendar.MONTH) + 1;
                    int day = now.get(Calendar.DAY_OF_MONTH);
                    path =  path + "/" + year + "/" + month + "/" + day;
                    File dirFile = new File(path);
                    if(!dirFile.exists()){
                        dirFile.mkdirs();
                    }
                    //输出流
                    File file = new File(path ,fileName);
                    OutputStream os = new FileOutputStream(file);
                    int len = -1;
                    byte[] buffer = new byte[1024];
                    while((len=is.read(buffer)) != -1){
                        os.write(buffer,0, len);
                    }
                    os.flush();
                    os.close();
                    is.close();
                    //删除临时文件夹的文件
                    item.delete();
                }
            }
            System.out.println("===========上传成功===========");
        } catch (FileUploadException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

Servlet3.0

<form action="${pageContext.request.contextPath }/uploadServlet" method="POST" enctype="multipart/form-data">
        文件:<input type="file" name="file"><br>
        <input type="submit" value="上传">
    </form>

package com.lijie.servlet;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;

@WebServlet("/uploadServlet")
@MultipartConfig
public class UploadServlet extends HttpServlet {
    
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        
        String path = this.getServletContext().getRealPath("/images");
        Part part = request.getPart("file");
        
        String header = part.getHeader("Content-Disposition");
        int indexOf = header.lastIndexOf("=");
        String fileName = header.substring(indexOf+2, header.length()-1);
        part.write(path+"/"+fileName);
    }

}

下载：

<a href="${pageContext.request.contextPath }/downloadServlet">跑车</a> <br>

package com.lijie.servlets;

import java.io.IOException;
import java.io.InputStream;

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

public class DownloadServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        
        String fileName = "超跑.jpg";
        
        // 打散：按当前的字符编码进行打散
        byte[] bytes = fileName.getBytes("UTF-8");
        // 组装：按目标字符编码进行组装
        fileName = new String(bytes, "ISO8859-1");
        
        // 修改响应的头部属性content-disposition值为attachment
        response.setHeader("content-disposition", "attachment;filename=" + fileName);
        
        // 获取连接服务端资源文件的输入流
        InputStream is = this.getServletContext().getResourceAsStream("/resources/aaa.jpg");
        // 获取输出流 
        ServletOutputStream os = response.getOutputStream();
        // 将输入流中的数据写入到输出流中
        int len = -1;
        byte[] buf = new byte[1024];
        while((len = is.read(buf)) != -1) {
            os.write(buf, 0, len);
        }        
        // 关闭流
        os.close();
        is.close();
    }
}