20160420javaweb之文件上传和下载
一、文件上传
1.提供表单允许用户通过表单选择文件进行上传
表单必须是POST提交
文件输入框必须有name属性,只有有name属性的输入项浏览器才会进行提交
需要设置enctype属性值为multipart/form-data
POST /Day15/upload.jsp HTTP/1.1
Accept: text/html, application/xhtml+xml, */*
Referer: http://localhost/Day15/upload.jsp
Accept-Language: zh-CN
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)
Content-Type: multipart/form-data; boundary=---------------------------7de1e62806e0
Accept-Encoding: gzip, deflate
Host: localhost
Content-Length: 394
Connection: Keep-Alive
Cache-Control: no-cache
Cookie: JSESSIONID=818C14110CA7BFD1FC90610866A220E8
-----------------------------7de1e62806e0
Content-Disposition: form-data; name="description1"
xxxx
-----------------------------7de1e62806e0
Content-Disposition: form-data; name="description2"
zzzz
-----------------------------7de1e62806e0
Content-Disposition: form-data; name="file1"; filename="ip.txt"
Content-Type: text/plain
192
-----------------------------7de1e62806e0--
2.在Servlet中将上传的文件保存在服务器的硬盘中
DiskFileItemFactory
public DiskFileItemFactory(int sizeThreshold, java.io.File repository)
public DiskFileItemFactory()
public void setSizeThreshold(int sizeThreshold) --用来设定内存缓冲区的大小,默认是10k
public void setRepository(java.io.File repository) --设定临时文件夹的大小
ServletFileUpload
boolean isMultipartContent(HttpServletRequest request) 判断上传表单是否为multipart/form-data类型
List parseRequest(HttpServletRequest request) 解析request对象，并把表单中的每一个输入项包装成一个fileItem 对象，并返回一个保存了所有FileItem的list集合。
setFileSizeMax(long fileSizeMax) 设置单个上传文件的最大值
setSizeMax(long sizeMax) 设置上传文件总量的最大值
setHeaderEncoding(java.lang.String encoding) 设置编码格式，解决上传文件名乱码问题
setProgressListener(ProgressListener pListener) 实时监听文件上传状态
FileItem
boolean isFormField() 判断FileItem是一个文件上传对象还是普通表单对象
示例代码：
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Insert title here</title> </head> <body> <h1>文件上传</h1><hr> <form action="${pageContext.request.contextPath }/UploadFileServlet" method="post" enctype="multipart/form-data"> 描述信息1：<input type="text" name="description1"/> 描述信息2：<input type="text" name="description2"/> <input type="file" name="file1"/> <input type="submit" value="上传"/> </form> </body> </html>
package com.dzq.web; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.util.List; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; 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; import com.dzq.utils.IOUtils; @WebServlet("/UploadFileServlet") public class UploadFileServlet extends HttpServlet { private static final long serialVersionUID = 1L; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { /*InputStream is=request.getInputStream(); byte[] bs=new byte[1024]; int i=0; while((i=is.read(bs))!=-1){ System.out.write(bs,0,i); } is.close();*/ try { //1.创建工厂 DiskFileItemFactory factory =new DiskFileItemFactory(); //2.生产文件上传核心类 ServletFileUpload fileupload=new ServletFileUpload(factory); //3.利用文件上传核心类解析request List<FileItem> list=fileupload.parseRequest(request); //4.遍历所有的fileitem for(FileItem item:list){ if(item.isFormField()){ //当前是普通字段项 String name=item.getFieldName(); String value=item.getString(); System.out.println(name+":"+value); }else{ //当前是一个文件上传项 String filename=item.getName(); InputStream in=item.getInputStream(); OutputStream out=new FileOutputStream(this.getServletContext().getRealPath("/upload"+filename)); IOUtils.In2Out(in, out); IOUtils.close(in, out); } } } catch (Exception e) { e.printStackTrace(); } } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }
package com.dzq.utils; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; public class IOUtils { private IOUtils(){ } public static void In2Out(InputStream in,OutputStream out) throws IOException{ byte[] bs=new byte[1024]; int i=0; while ((i=in.read(bs))!=-1) { out.write(bs,0,i); } } public static void close(InputStream in,OutputStream out){ if(in!=null){ try { in.close(); } catch (IOException e) { e.printStackTrace(); }finally{ in=null; } } if(out!=null){ try { out.close(); } catch (IOException e) { e.printStackTrace(); }finally{ out=null; } } } }
如果是一个普通字段项可以调用:
String getFieldName() 获得普通表单对象的name属性
String getString(String encoding) 获得普通表单对象的value属性，可以用encoding进行编码设置
如果是一个文件上传项:
String getName() 获得上传文件的文件名（有些浏览器会携带客户端路径）
InputStream getInputStream() 获得上传文件的输入流
delete() 在关闭FileItem输入流后，删除临时文件
文件存放应该注意的问题:
1.upload文件夹和temp文件夹都要放在web-inf目录下保护起来,防止上传入侵和访问其他用户上传资源的问题
2.文件名要拼接uuid保证唯一
3.文件要分目录存储保证同一目录下不要有过多的文件,分目录的算法有很多,介绍了一种根据hash值分目录算法
文件上传的一些细节：
package com.itheima.web; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.math.BigDecimal; import java.util.List; import java.util.UUID; import javax.servlet.ServletException; 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.ProgressListener; import org.apache.commons.fileupload.FileUploadBase.FileSizeLimitExceededException; import org.apache.commons.fileupload.disk.DiskFileItemFactory; import org.apache.commons.fileupload.servlet.ServletFileUpload; import com.itheima.util.IOUtils; public class UploadServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8"); try{ //1.创建工厂 DiskFileItemFactory factory = new DiskFileItemFactory(); factory.setSizeThreshold(100*1024); factory.setRepository(new File(this.getServletContext().getRealPath("WEB-INF/temp"))); //2.生产文件上传核心类 ServletFileUpload fileUpload = new ServletFileUpload(factory); //--检查是否是正确的文件上传表单 if(!fileUpload.isMultipartContent(request)){ throw new RuntimeException("请用正确的表单进行上传!"); } //--设置文件上传的大小限制 // fileUpload.setFileSizeMax(1024*1024*100);//单个文件不大于10M // fileUpload.setSizeMax(1024*1024*100);//总大小不大于100M //--设置编码集,解决上传文件名的乱码问题 fileUpload.setHeaderEncoding("utf-8"); //--设置文件上传监听 fileUpload.setProgressListener(new ProgressListener(){ Long beginTime = System.currentTimeMillis(); public void update(long bytesRead, long contentLength, int items) { BigDecimal br = new BigDecimal(bytesRead).divide(new BigDecimal(1024),2,BigDecimal.ROUND_HALF_UP); BigDecimal cl = new BigDecimal(contentLength).divide(new BigDecimal(1024),2,BigDecimal.ROUND_HALF_UP); System.out.print("当前读取的是第"+items+"个上传项,总大小"+cl+"KB,已经读取"+br+"KB"); //剩余字节数 BigDecimal ll = cl.subtract(br); System.out.print("剩余"+ll+"KB"); //上传百分比 BigDecimal per = br.multiply(new BigDecimal(100)).divide(cl,2,BigDecimal.ROUND_HALF_UP); System.out.print("已经完成"+per+"%"); //上传用时 Long nowTime = System.currentTimeMillis(); Long useTime = (nowTime - beginTime)/1000; System.out.print("已经用时"+useTime+"秒"); //上传速度 BigDecimal speed = new BigDecimal(0); if(useTime!=0){ speed = br.divide(new BigDecimal(useTime),2,BigDecimal.ROUND_HALF_UP); } System.out.print("上传速度为"+speed+"KB/S"); //大致剩余时间 BigDecimal ltime = new BigDecimal(0); if(!speed.equals(new BigDecimal(0))){ ltime = ll.divide(speed,0,BigDecimal.ROUND_HALF_UP); } System.out.print("大致剩余时间为"+ltime+"秒"); System.out.println(); } }); //3.利用文件上传核心类解析request List<FileItem> list = fileUpload.parseRequest(request); //4.遍历所有的FileItem for(FileItem item : list){ if(item.isFormField()){ //当前是一个普通的字段项 String name = item.getFieldName(); String value = item.getString("utf-8"); System.out.println(name+":"+value); }else{ //当前是一个文件上传项 String filename = item.getName(); String uuidName = UUID.randomUUID().toString()+"_"+filename; int hash = uuidName.hashCode(); String hashStr = Integer.toHexString(hash); char [] hss = hashStr.toCharArray(); String path = this.getServletContext().getRealPath("WEB-INF/upload"); for(char c : hss){ path+="/"+c; } new File(path).mkdirs(); InputStream in = item.getInputStream(); OutputStream out = new FileOutputStream(new File(path,uuidName)); IOUtils.In2Out(in, out); IOUtils.close(in, out); //--删除临时文件 item.delete(); } } }catch (FileSizeLimitExceededException e) { response.getWriter().write("单个文件不超过10M,总大小不超过100M!"); return; }catch (Exception e) { e.printStackTrace(); throw new RuntimeException(e); } } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }
二、文件下载
response.setHeader("Content-Disposition", "attachment;filename="+URLEncoder.encode(filename,"utf-8"));
response.setContentType(this.getServletContext().getMimeType(filename));//MIME类型
下载示例源码：
package com.dzq.web; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.net.URLEncoder; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import com.dzq.utils.IOUtils; @WebServlet("/DownServlet") public class DownServlet extends HttpServlet { private static final long serialVersionUID = 1L; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //1.获取要下载的资源的名称 String filename = request.getParameter("file"); response.setHeader("Content-Disposition", "attachment;filename="+URLEncoder.encode(filename,"utf-8")); response.setContentType(this.getServletContext().getMimeType(filename));//MIME类型 InputStream in = new FileInputStream(this.getServletContext().getRealPath("/"+filename)); OutputStream out = response.getOutputStream(); IOUtils.In2Out(in, out); IOUtils.close(in, null); //2.读取资源 } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }
