1、jsp頁面：

<a href="<%=path%>/accessoryFile/download.action?fileName=${flag.fileName}&inputPath=/download/${flag.fileName}">下載</a>

2.struts2.xml

<!-- 附件下載 -->
  <action name="download" class="accessoryFileAction"
   method="accessoryFileActionMethod">
   <result name="success" type="stream">
       <param name="contentType">
        application/octet-stream;charset=ISO8859-1
       </param>
    <param name="inputName">inputStream</param>
    <param name="contentDisposition">
     attachment;filename="${downloadFileName}"
    </param>
    <param name="bufferSize">4096</param>
   </result>
   <result name="error">/admin/adminError.jsp</result>
  </action>

3.action類：

import java.io.File;
import java.io.FileNotFoundException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class AccessoryFileAction extends ActionSupport

// 附件下找文件名稱
 private String fileName;
 // 下載路徑
 private String inputPath;
 //文件下載到客戶時文件名稱
 private String downloadFileName;
 private InputStream inputStream;
 //附件說明
 private String fileMsg;
 //附件類型及附件名稱
 private String typeStr;
 //取得IO流
 public InputStream getInputStream() throws Exception {
  return ServletActionContext.getServletContext().getResourceAsStream(inputPath);
 }

/**
  * 附件下載方法
  *
  * @return
  */
 public String accessoryFileActionMethod() throws Exception {
  // 提供下載的目錄
  String downloadDir = ServletActionContext.getServletContext()
    .getRealPath("/download");
  // 文件下載的路徑      
  String downloadFile = ServletActionContext.getServletContext()
    .getRealPath(inputPath);
  // 真實文件路徑
  try {
   downloadFile = new String(downloadFile.getBytes("ISO-8859-1"), "utf-8");
  } catch (UnsupportedEncodingException e) {
   System.out.println("轉(zhuǎn)換異常");
  }
  // 發(fā)現(xiàn)不是指定文件目錄就返回NULL
  if (!downloadFile.startsWith(downloadDir)) {
   return null;
  }
  return SUCCESS;
 }

/**
  * 拼接下載后文件名稱及后綴名
  * @return
  */
 public String getDownloadFileName() {
  String downFileName = fileName;
  try {
         //用服務(wù)器的文件名作為下載后的文件名
  downFileName = new String(downFileName.getBytes(),"ISO8859-1");
  } catch (UnsupportedEncodingException e) {
   System.out.println("UnsupportedEncodingException 異常 ");
  }
  return downFileName;
  
  }

public String getUploadFileName() {
  String temp = new SimpleDateFormat("yyyyMMddhhmmss").format(Calendar.getInstance().getTime()).toString();
  return temp+".doc";
 }

 public void setFileName(String fileName) {
  this.fileName = fileName;
  try {
   fileName = new String(fileName.getBytes("ISO-8859-1"), "utf-8");
  } catch (UnsupportedEncodingException e) {
   System.out.println("轉(zhuǎn)換異常");
  }
 }

 public void setInputPath(String inputPath) {
  this.inputPath = inputPath;
  try {
   inputPath = new String(inputPath.getBytes("ISO-8859-1"), "utf-8");
  } catch (UnsupportedEncodingException e) {
   System.out.println("轉(zhuǎn)換異常");
  }
 }

get and set 方法略