struts2实现文件下载功能

Z时代
2024-01-10
分类：IT

文件下载是一个很常见的功能，用struts2实现文件下载的步骤：

一）、定义一个Action类，FileDownload.java


package com.struts2.filedownload; 
import java.io.InputStream;  
import org.apache.struts2.ServletActionContext;  
import com.opensymphony.xwork2.ActionSupport; 
//文件下载 
public class FileDownload extends ActionSupport{ 
 private int number ; 
 private String fileName; 
 public int getNumber() { 
  return number; 
 } 
 public void setNumber(int number) { 
  this.number = number; 
 } 
 public String getFileName() { 
  return fileName; 
 } 
 public void setFileName(String fileName) { 
  this.fileName = fileName; 
 } 
 //返回一个输入流，作为一个客户端来说是一个输入流，但对于服务器端是一个 输出流 
 public InputStream getDownloadFile() throws Exception 
 { 
  if(1 == number) 
  { 
   this.fileName = "Dream.jpg" ; 
   //获取资源路径 
   return ServletActionContext.getServletContext().getResourceAsStream("upload/Dream.jpg") ; 
  } 
  else if(2 == number) 
  { 
   this.fileName = "jd2chm源码生成chm格式文档.rar" ; 
   //解解乱码 
   this.fileName = new String(this.fileName.getBytes("GBK"),"ISO-8859-1"); 
   return ServletActionContext.getServletContext().getResourceAsStream("upload/jd2chm源码生成chm格式文档.rar") ; 
  } 
  else 
   return null ; 
 } 
 @Override 
 public String execute() throws Exception { 
  return SUCCESS; 
 } 
}

二）、在struts.xml文件中配置相关信息


<struts>  
 <package name="struts2" extends="struts-default">  
  <action name="FileDownload" class="com.struts2.filedownload.FileDownload"> 
   <result name="success" type="stream"> 
    <param name="contentType">text/plain</param> 
    <param name="contentDisposition">attachment;fileName="${fileName}"</param> 
    <param name="inputName">downloadFile</param> 
    <param name="bufferSize">1024</param> 
   </result> 
  </action> 
 </package> 
</struts>

1.结果类型必须要写成 type="stream" ,与之对应的处理类是 org.apache.struts2.dispatcher.StreamResult

2.涉及到的参数：

1) <param name="contentDisposition">attachment;fileName="${fileName}"</param>

contentDisposition默认是 inline（内联的), 比如说下载的文件是文本类型的，就直接在网页上打开，不能直接打开的才会打开下载框自己选择

2) attachment ：下载时会打开下载框

3) fileName="${fileName}" ：在这定义的名字是一个动态的，该名字是显示在下载框上的文件名字

4. <param name="inputName">downloadFile</param> ，这个downloadFile名字要和FileDownload.java类中的getDownloadFile()方法名去掉get 一致

三）用于显示下载的链接界面 filedownload.jsp


<%@ 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%>" rel="external nofollow" > 
 <title>My JSP 'filedownload.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" rel="external nofollow" > 
 --> 
 </head> 
 <body> 
 <h2>文件下载内容：</h2><br/> 
 Dream.jpg:<a href="FileDownload.action?number=1" rel="external nofollow" >点击下载</a><br/> 
 jd2chm源码生成chm格式文档.rar:<a href="FileDownload.action?number=2" rel="external nofollow" >点击下载2</a> 
 </body> 
</html>