Java之Servlet文件下载20190228-优快云博客

本文介绍了一种使用JSP和Servlet实现文件下载的方法。通过设置HTTP响应头，可以触发浏览器下载特定URL指定的文件，包括JSP、图片等资源。文章提供了完整的代码示例，展示了如何从Web应用中下载文件。

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jsp页面:

<%@ 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>
<a href="DownloadServlet?urlStr=index.jsp">下载index.jsp</a>
<a href="DownloadServlet?urlStr=photo/1.jpg">下载1.jpg</a>
<a href="DownloadServlet?urlStr=test.jsp">下载test.jsp</a>
</body>
</html>

Servlet:

package org.jimmy.testwebproject2019012602.servlet.download;

import java.io.FileInputStream;
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;

/**
 * @author Yang.Yuxin(Jimmy)
 * @date 2019年2月14日 下午5:39:47
 * @detail 下载Servlet
 */
public class DownloadServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        try {
            request.setCharacterEncoding("utf-8");
            response.setCharacterEncoding("utf-8");
            String urlStr = request.getParameter("urlStr");
            String fileName = urlStr.substring(urlStr.lastIndexOf("/") + 1);
            response.setContentType("application/x-msdownload; charset=utf-8");
            response.addHeader("Content-Disposition", "attachment; filename=" + fileName);
            //这个是使用项目的相对路径来获取文件的输入流
            InputStream is = request.getServletContext().getResourceAsStream(urlStr);
            /*
            //这个可以使用绝对路径来获取文件的输入流
            FileInputStream fis = new FileInputStream("D:\\Document\\201902\\20190228\\Test\\1.jpg");
            */
            ServletOutputStream sos = response.getOutputStream();
            int fileLength = is.available();
            int cacheLength = 1024;
            if(fileLength < cacheLength) {
                cacheLength = fileLength;
            }
            int len = cacheLength;
            byte[] bytes = new byte[cacheLength];
            while((len = is.read(bytes, 0, len)) != -1) {
                sos.write(bytes);
            }
            sos.flush();
            sos.close();
            is.close();
        }catch(Exception e) {
            e.printStackTrace();
        }
        
    }

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