这是一个Struts2的例子来说明使用定制返回类型，允许用户下载文件。web工程的文件夹结构如下所示：
1. Action
在Action类中，声明一个 InputStream 的数据类型和getter方法。
DownloadAction.java
package com.yiibai.common.action;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import com.opensymphony.xwork2.ActionSupport;
public class DownloadAction extends ActionSupport{
private InputStream fileInputStream;
public InputStream getFileInputStream() {
return fileInputStream;
}
public String execute() throws Exception {
fileInputStream = new FileInputStream(new File("C:\file-for-download.txt")); return SUCCESS;
}
}
2. 视图文件
一个正常的页面，有一个下载链接，用于下载文件。
downloadPage.jsp
<%@ taglib prefix="s" uri="/struts-tags" %>
<html>
<body>
<h1>Struts 2 download file example</h1>
<s:url id="fileDownload" namespace="/" action="download" ></s:url>
<div><div class="ads-in-post hide_if_width_less_800">
<script async src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>
<!-- 728x90 - After2ndH4 -->
<ins class="adsbygoogle hide_if_width_less_800"
style="display:inline-block;728px;height:90px"
data-ad-client="ca-pub-2836379775501347"
data-ad-slot="3642936086"
data-ad-region="yiibairegion"></ins>
<script>
(adsbygoogle = window.adsbygoogle || []).push({});
</script>
</div></div><h2>Download file - <s:a href="%{fileDownload}">fileABC.txt</s:a>
</h2>
</body>
</html>
3. struts.xml
定义下载文件的细节。 <param name=”inputName”> 值是从Action的InputStream属性的名称。
阅读Struts2的数据流结果文档以了解更详细信息。
struts.xml
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN" "http://struts.apache.org/dtds/struts-2.0.dtd"> <struts> <constant name="struts.devMode" value="true" /> <package name="default" namespace="/" extends="struts-default"> <action name="show"> <result name="success">pages/downloadPage.jsp</result> </action> <action name="download" class="com.yiibai.common.action.DownloadAction"> <result name="success" type="stream"> <param name="contentType">application/octet-stream</param> <param name="inputName">fileInputStream</param> <param name="contentDisposition">attachment;filename="file-for-download.txt"</param> <param name="bufferSize">1024</param> </result> </action> </package> </struts>
4. 执行结果
在浏览器中打开：http://localhost:8080/struts2download/
参考
- http://struts.apache.org/2.x/docs/stream-result.html
- http://www.iana.org/assignments/media-types/
- http://www.yiibai.com/struts/struts-download-file-from-website-example.html
- http://www.yiibai.com/java/how-to-download-file-from-website-java-jsp.html
- http://struts.apache.org/2.x/docs/how-can-we-return-a-text-string-as-the-response.html
代码下载(struts2download) - http://pan.baidu.com/s/1jGg0Lzo