Servlet实现web站点文件下载功能示例详解编程语言

1、首先创建一个SharedFilesServlet用于返回一个文件分享界面

package com.hyman.view; 
 
import java.io.IOException; 
import java.io.PrintWriter; 
 
import javax.servlet.ServletException; 
import javax.servlet.http.HttpServlet; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 
 
/** 
 * Servlet implementation class SharedFilesServlet 
 */ 
public class SharedFilesServlet extends HttpServlet { 
    private static final long serialVersionUID = 1L; 
        
    /** 
     * @see HttpServlet#HttpServlet() 
     */ 
    public SharedFilesServlet() { 
        super(); 
        // TODO Auto-generated constructor stub 
    } 
 
    /** 
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) 
     */ 
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
        // TODO Auto-generated method stub 
        response.setContentType("text/html; charset=utf-8");  
        PrintWriter out = response.getWriter(); 
        out.println("<script type='text/javascript' language='javascript'>" 
                + "function fileDown(obj){" 
                + "var resourceName = '';" 
                + "var buttonId = obj.getAttribute('id');" 
                + "var eleName = buttonId.substring(0,3) + 'File';"             
                + "resourceName = document.getElementsByName(eleName)[0].value;" 
                + "var url = '/SharingSite/DownFileServlet?fileName=' + resourceName;" 
                + "window.location.href=url;" 
                + "}" 
                + "</script>"); 
        out.println("<h1>文件共享网站</h1>"); 
        out.println("mp3资源：<input type='text' name='mp3File' />&nbsp;&nbsp;&nbsp;&nbsp;<input type='submit' value ='点击下载' id='mp3Down' onclick='fileDown(this)' /><br/>"); 
        out.println("avi资源：<input type='text' name='aviFile' />&nbsp;&nbsp;&nbsp;&nbsp;<input type='submit' value ='点击下载' id='aviDown' onclick='fileDown(this)' /><br/>"); 
        out.println("jpg资源：<input type='text' name='jpgFile' />&nbsp;&nbsp;&nbsp;&nbsp;<input type='submit' value ='点击下载' id='jpgDown' onclick='fileDown(this)' /><br/>"); 
        out.println("txt资源：<input type='text' name='txtFile' />&nbsp;&nbsp;&nbsp;&nbsp;<input type='submit' value ='点击下载' id='txtDown' onclick='fileDown(this)' /><br/>"); 
    } 
 
    /** 
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) 
     */ 
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
        // TODO Auto-generated method stub 
        this.doGet(request, response); 
    } 
 
}

2、然后创建一个控制器，来判断是否盗链，以及处理文件下载逻辑：

package com.hyman.controller; 
 
import java.io.File; 
import java.io.FileInputStream; 
import java.io.IOException; 
import java.io.OutputStream; 
 
import javax.servlet.ServletException; 
import javax.servlet.http.HttpServlet; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 
 
/** 
 * Servlet implementation class DownFileServlet 
 */ 
public class DownFileServlet extends HttpServlet { 
    private static final long serialVersionUID = 1L; 
        
    /** 
     * @see HttpServlet#HttpServlet() 
     */ 
    public DownFileServlet() { 
        super(); 
        // TODO Auto-generated constructor stub 
    } 
 
    /** 
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) 
     */ 
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
        // TODO Auto-generated method stub 
        response.setContentType("text/html; charset=utf-8"); 
        String referer = request.getHeader("Referer"); 
        if (referer == null || !referer.startsWith("http://localhost:8080/SharingSite/")) { 
            response.sendRedirect("/SharingSite/AntiPirateLink"); 
        } else { 
            String fileName = request.getParameter("fileName"); 
            response.setHeader("Content-Disposition", "attachment; filename="+fileName); 
            String path = this.getServletContext().getRealPath("/resources/"+fileName); 
            FileInputStream fis = null; 
            OutputStream os = null; 
            try { 
                fis = new FileInputStream(new File(path)); 
                byte buff[] = new byte[1024]; 
                int len = 0; 
                os = response.getOutputStream(); 
                while ((len = fis.read(buff)) > 0) { 
                    os.write(buff, 0, len); 
                } 
            } catch (Exception e) { 
                e.printStackTrace(); 
                throw new RuntimeException(); 
            } finally { 
                if (os != null) os.close(); 
                if (fis != null) fis.close(); 
            } 
        } 
         
    } 
 
    /** 
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) 
     */ 
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
        // TODO Auto-generated method stub 
        this.doGet(request, response); 
    } 
 
}

3、创建一个AntiPirateLink返回盗链提醒界面，并在10秒后自动刷新跳转到SharedFilesServlet

package com.hyman.view; 
 
import java.io.IOException; 
import java.io.PrintWriter; 
 
import javax.servlet.ServletException; 
import javax.servlet.http.HttpServlet; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 
 
/** 
 * Servlet implementation class AntiPirateLink 
 */ 
public class AntiPirateLink extends HttpServlet { 
    private static final long serialVersionUID = 1L; 
        
    /** 
     * @see HttpServlet#HttpServlet() 
     */ 
    public AntiPirateLink() { 
        super(); 
        // TODO Auto-generated constructor stub 
    } 
 
    /** 
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) 
     */ 
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
        // TODO Auto-generated method stub 
        response.setContentType("text/html; charset=utf-8"); 
        PrintWriter out = response.getWriter(); 
        out.println("<script type='text/javascript' language='javascript'>" 
                + "var i = 10;" 
                + "function showTime(){" 
                + "if(i > 0) {document.getElementById('time').innerHTML = '请不要盗链下载... ' + i +' 秒后自动跳转到下载首页...';" 
                + "i--;}" 
                + "}" 
                + "setInterval('showTime()',1000);" 
                + "</script>"); 
        out.println("<span id='time'>"); 
        response.setHeader("Refresh", "10; url=/SharingSite/SharedFilesServlet"); 
    } 
 
    /** 
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) 
     */ 
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
        // TODO Auto-generated method stub 
        this.doGet(request, response); 
    } 
 
}

【分析】文件下载部分实现步骤：

【分析】文件下载部分实现步骤：

1、response.setHeader(“Content-Disposition”, “attachment; filename=”+fileName);在http回复消息头中的Content-Disposition中指明下文件的文件名；

2、调用this.getServletContext().getRealPath(“/resources/”+fileName);函数获取到文件的全路径；

3、使用文件流FileInputStream将文件读入到服务器内存，重要要用到缓存处理，然后再调用response的getOutputStream()方法获得向客户端写文件的输出文件流；

来自：
http://www.cnblogs.com/page-of-Hyman/p/4321523.html