通过Struts2下载文件, 流式.

处理下载的Action:

package com.jyu.maven.MyWebApp;

import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;

import javax.servlet.http.HttpServletResponse;

import org.apache.struts2.ServletActionContext;
import com.opensymphony.xwork2.ActionSupport;

public class DownloadFileAction extends ActionSupport {
    
    private static String ROOTDIR = "d:\\"; //文件存放目录

    private String downFileName;
    private String mimeType;
    private InputStream fileInputStream;

    public InputStream getFileInputStream() {// 下载文件的输出流
        File file = new File(ROOTDIR, downFileName);
        
        try {
            fileInputStream = new FileInputStream(file);
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            System.err.println("路径有问题");
        }
        if (fileInputStream == null) {
            fileInputStream = new ByteArrayInputStream(
                    "Sorry,File not found !".getBytes());
        }
        return fileInputStream;
    }

    public String getMimeType() {
        return mimeType;
    }

    public String getDownFileName() {
        String FileName = downFileName;

        try {
　　　　　　　//对文件名转码, 不然在下载的时候文件名是乱码.
            FileName = new String(FileName.getBytes(), "ISO8859-1");

        } catch (UnsupportedEncodingException e) {

            e.printStackTrace();

        }
        return FileName;
    }

    public void setDownFileName(String downFileName) {
        this.downFileName = downFileName;
    }

    public String execute() throws Exception {
        File file = new File(ROOTDIR, downFileName);

　　　　 //在响应头里加入文件长度信息
        HttpServletResponse response = ServletActionContext.getResponse();
        response.addHeader("content-length", String.valueOf(file.length()));
        

　　　　 //获取文件类型
        mimeType = ServletActionContext.getServletContext().getMimeType(
                downFileName);
        return SUCCESS;
    }

}

struts.xml的配置:

<action name="fileDownload" class="com.jyu.maven.MyWebApp.DownloadFileAction">
            <!-- 设置文件名参数，由页面上传入 -->
            <param name="downFileName"></param>
            <result name="success" type="stream">
                <!-- 下载文件类型定义 -->
                <param name="contentType">${mimeType}</param>
                <!-- 下载文件处理方法 -->
                <param name="contentDisposition">
                    attachment;filename="${downFileName}"
                </param>
                <!-- 下载文件输出流定义 getFileInputStream() -->
                <param name="inputName">fileInputStream</param>
                <param name="bufferSize">1024</param>
            </result>
</action>

在html页面, 将下载链接指定到fileDownload.action, 并将downFileName作为参数传入, 如果存在该文件, 就可以下载文件了. 

这种方式的确定是下载文件是流式的, 迅雷等下载工具无法暂停下载, 暂停后需要重新开始.