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servlet实现文件上传和下载

2018-03-25 22:54 351 查看

servlet实现文件上传注意事项：

表单提交方式应为post方式，还要设置表单属性enctype=”multipart/form”

使用Part对象来获取上传文件的相关属性以及获取文件的输入流

上传到服务器的路径一定要是绝对路径

设置编码格式防止中文名乱码

使用@MultipartConfig标注Servlet

servlet实现文件下载注意事项：

设置response对象的ContentType为对应的文件类型

取得下载文件在服务器上的真实路径

文件上传servlet:

package com.ysgncss;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;

import javax.servlet.ServletContext;
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("/UploadFile.do")
@MultipartConfig  //表示期望multipart/data-form MIME类型
public class UploadFile extends HttpServlet {
private static final long serialVersionUID = 1L;

public UploadFile() {
super();
}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
//1.获取上传文件的文件名
Part filepart=request.getPart("filename");
String conf=filepart.getHeader("content-disposition");
String filename="";
//从头信息中获取文件名
for (String content : conf.split(";")) {
if (content.trim().startsWith("filename")) {
filename=content.substring(content.indexOf("\"")+1, content.lastIndexOf("\""));
}
}

//2.利用输入输出流传输数据
OutputStream out =null;
InputStream in=null;
ServletContext context=getServletContext();
PrintWriter writer=response.getWriter();
String path=context.getRealPath("/upload");
try {
//构造到指定目录的输出流
out=new FileOutputStream(new File(path+File.separator+filename));
//获取上传文件输入流
in=filepart.getInputStream();
int read;
byte b[]=new byte[1024];
while((read=in.read(b))!=-1){
out.write(b, 0, read);
}
writer.write("文件上传成功至"+path);
} catch (FileNotFoundException e) {
writer.write("没有指定上传文件 上传失败");
}finally{
in.close();
out.close();
}
}
}

文件上传html代码

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" type="text/css" href="css/bootstrap.min.css">
<title>上传页面</title>
</head>
<body>
<form action="UploadFile.do"  method="post"  enctype="multipart/form-data">
<h4>请选择文件：</h4><input type="file"  name="filename"><br>
<input type="submit"  value="login">
</form>

<script src="https://cdn.bootcss.com/jquery/3.2.1/jquery.slim.min.js" ></script>
<script type="text/javascript"  src="js/bootstrap.min.js"></script>
</body>
</html>

文件下载Servlet代码：

package com.ysgncss;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/download.do")
public class DownloadServlet extends HttpServlet {
private static final long serialVersionUID = 1L;

public DownloadServlet() {
super();
}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("UTF-8");
response.setCharacterEncoding("UTF-8");
response.setContentType("application/pdf");
ServletContext servletContext=this.getServletContext();
String downloadFilename=request.getParameter("filename");
//建议游览器保存文件
response.setHeader("Content-Disposition", "attachment;filename="+downloadFilename);

//得到真实路径
String realpath=servletContext.getRealPath("/download/"+downloadFilename);

try {
//获取文件输入流
InputStream in=new FileInputStream(new File(realpath));
//获取输出流
OutputStream out=response.getOutputStream();
int read=0;
byte[] bytes=new byte[1024];
while((read=in.read(bytes))!=-1){
out.write(bytes, 0, read);
}
out.flush();
out.close();
in.close();
} catch (Exception e) {
System.out.println(e.getMessage());
}
}

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}

文件下载html代码

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" type="text/css" href="css/bootstrap.min.css">
<title>下载页面</title>
</head>
<body>
<h1>点击<a href="download.do?filename=python.pdf">这里</a>下载</h1>
<script src="https://cdn.bootcss.com/jquery/3.2.1/jquery.slim.min.js" ></script>
<script type="text/javascript"  src="js/bootstrap.min.js"></script>
</body>
</html>

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标签： servlet 文件上传文件下载

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