文件通过流的方式下载时的文件名设置

response.addHeader("Content-Disposition", "attachment;filename="); 

这里的文件名最好用URLDecode.decode(fileName, "UTF-8")处理过，不然中文会有乱码

Servlet例子：

package com.cj.test1_10;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URLEncoder;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class Test9
 */
@WebServlet("/Test9")
public class Test9 extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    public Test9() {
        super();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取文件的绝对路径
        String realPath = this.getServletContext().getRealPath("/就来中文.jpg");
        System.out.println("realPath:"+realPath);
        //获取要下载的文件名
        String fileName = realPath.substring(realPath.lastIndexOf("\\")+1);
        System.out.println("fileName:"+fileName);
        //设置响应头，以下载的形式打开文件
        response.setHeader("content-disposition", "attachment;fileName="+URLEncoder.encode(fileName, "UTF-8"));
        //获取要下载的文件输入流
        InputStream in = new FileInputStream(realPath);
        int len = 0;
        //创建数据缓冲区
        byte [] buffer = new byte[1024];
        //创建输出流
        ServletOutputStream out = response.getOutputStream();
        while((len = in.read(buffer))>0){
            out.write(buffer, 0, len);
        }
    }

}