struts2在项目中的应用之下载

文件下载是一个非经常见的功能，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client来说是一个输入流，但对于server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源代码生成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源代码生成chm格式文档.rar") ;
        }
        else
           return null ;
    }
    @Override
    public String execute() throws Exception {
        return SUCCESS;
    }
}

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client来说是一个输入流。但对于server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源代码生成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源代码生成chm格式文档.rar") ;
		}
		else
		   return null ;
	}
	
	@Override
	public String execute() throws Exception {
		
		return SUCCESS;
	}

}

二)在struts.xml文件里配置相关信息

<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>

<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.结果类型必需要写成 type="stream"  ,与之相应的处理类是 org.apache.struts2.dispatcher.StreamResult

2.涉及到的參数：

3.

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

     contentDisposition默认是 inline（内联的), 比方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称字

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%>">
    <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">
    -->
  </head>
  <body>
    <h2>文件下载内容：</h2><br/>
    Dream.jpg:<a href="FileDownload.action?number=1">点击下载</a><br/>
    jd2chm源代码生成chm格式文档.rar:<a href="FileDownload.action?number=2">点击下载2</a>
  </body>
</html>