Struts 2 Download file example- How to configure the file name dynamically?

In this tutorial, i am going to show you how to download file in struts 2 using custom result type configured in struts.xml.
jsp page code with download link to download a file.
downloadFile.jsp

<%@ taglib prefix="s" uri="/struts-tags" %>

<h1>Struts 2 download file example</h1>

<s:url id="downloadFile" action="downloadFile"></s:url>
<s:a href="%{downloadFile}"  title="Download File">Click here to dowload file</s:a>

struts.xml
The <param name="inputName">fileInputStream</param> value i.e. fileInputStream  is the name of the InputStream property from the Action class and in <param name="contentDisposition">attachment;filename="${fileName}</param> , ${fileName} where fileName is same fileName property from the Action class.

<?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" extends="struts-default">
   <action name="downloadFile" class="com.jk.downloadAction" method="downloadFile">
      <interceptor-ref name="fileUpload">
           <param name="maximumSize">5048000000</param>
           <param name="allowedTypes">text/plain</param>
      </interceptor-ref>
      <interceptor-ref name="defaultStack"></interceptor-ref>
      <result name="success" type="stream">
           <param name="contentType">application/octet-stream</param>
           <param name="inputName">fileInputStream</param>
           <param name="contentDisposition">attachment;filename="${fileName}</param>
           <param name="bufferSize">1024</param>
       </result>
   </action>
</package>
 
</struts>

DownloadAction.java

public class DownloadAction
{
  private InputStream fileInputStream;
  private String fileName; 
  public String writeErrorFile(final Map errorMap)
                        throws IOException {
      setFileName("file.txt");
      StringBuffer buffer = new StringBuffer();
                   buffer.append("Content to show");
                   fileInputStream = new ByteArrayInputStream(buffer.toString().getBytes());

                   return SUCCESS;
        }
   public InputStream getFileInputStream() {
  return fileInputStream;
 }
   public String getFileName() {
  return fileName;

 }
   pulic void setFileName(String fileName) {
  this.fileName = fileName;
 }
}

References:
1. http://struts.apache.org/development/2.x/docs/stream-result.html
2.http://struts.apache.org/development/2.x/docs/how-can-we-return-a-text-string-as-the-response.html