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JSP+Servlet实现上传下载

2016-07-08 10:51 288 查看

0.项目结构

1.在WebRoot下创建index.jsp页面

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">

<title>My JSP 'index.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>

<body>
<form action="UploadServlet" enctype="multipart/form-data" method="post">
<p>姓名：<input type="text" name="user"/></p>
<p>选择图片：<input type="file" name="nfile"/></p>
<p><input type="submit" value="提交"/></p>
</form>
</body>
</html>

2.在src下的com.servlet包下创建UploadServlet.java文件

package com.servlet;

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.List;

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.FileUploadBase;
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 {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//1.乱码处理
request.setCharacterEncoding("UTF-8");
response.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=UTF-8");
//创建输出流对象（负责在前台页面（写入）打印内容的）
PrintWriter out=response.getWriter();

//2.得知请求中的数据是否包含二进制数据
boolean isMultipart=ServletFileUpload.isMultipartContent(request);

//3.如果包含
if(isMultipart){
//3.1 创建封装表单数据的对象
DiskFileItemFactory factory=new DiskFileItemFactory();

//3.2 设置文件缓冲区大小4KB
factory.setSizeThreshold(4096);

//3.3 创建上传表单数据的对象
ServletFileUpload upload=new ServletFileUpload(factory);

//3.4 设置上传单个文件的最大限制
upload.setSizeMax(1024*30);

try {
//3.5 解析请求中上传的表单数据，并将解析的内容的放入list集合
List<FileItem> filelist=upload.parseRequest(request);

//3.6 循环存放表单数据的集合把普通字段和二进制字段取出来
for (FileItem f : filelist) {
//3.6.1 如果是普通字段
if(f.isFormField()){
//(1)获取普通字段的name属性值：user
String normalFiled=f.getFieldName();

//(2)判断如果name属性值是想要的就取对应值
if(normalFiled.equals("user")){
//输出name属性所对应的value值
out.print(f.getString("UTF-8")+"上传了文件！<br/>");
}

}else{
//3.6.2 如果是二进制文件字段
//(1)获取上传的文件名
String uploadFileName=f.getName();

//(2)通过Arrays的aslist方法创建固定的集合，规定的文件格式
List<String> fileType=Arrays.asList("gif","bmp","jpg","png");

//(3)返回文件的后缀
String ext=uploadFileName.substring(uploadFileName.lastIndexOf(".")+1);

//(4)判断文件类型是否允许在制定范围
if(fileType.contains(ext)){
//(4.1)判断如果文件名不为空，将数值取出
if(uploadFileName!=null && !uploadFileName.equals("")){
//(4.1.1)获取上传的文件路径
String uploadFilePath=
request.getSession().getServletContext().getRealPath("upload/");

//拼接路径：第一个参数是文件夹，第二个参数是文件名
File saveFile=new File(uploadFilePath,f.getName());

//(4.1.2)上传到服务器
f.write(saveFile);

out.print("上传成功后的文件名是："+uploadFileName+",文件大小是："+f.getSize()+"bytes!<br/>");
out.print("上传的文件夹路径："+uploadFilePath+"<br/>");
out.print("上传的文件全路径："+saveFile.getAbsolutePath()+"<br/>");

}else{
out.print("二进制文件名为空！");
}
}else{
out.print("文件上传失败！，文件类型只能是gif.bmp,jpg,png");
}
}
}

} catch (FileUploadBase.SizeLimitExceededException e) {
out.print("文件上传失败，文件太大，单个文件的最大限制是："+upload.getSizeMax()+"bytes!!") ;
e.printStackTrace();
} catch (FileUploadException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}else{
//4.不包含
out.print("表单中不包含二进制数据！");
}

}

}

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