servlet-下载文件

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.URLEncoder;

public class FileServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 获取下载文件路径
        String realPath = this.getServletContext().getRealPath("E:\\dd.txt");
        // 获取文件名称
        String fileName = realPath.substring(realPath.lastIndexOf("\\")+1);
        // 相应的消息头
        resp.setHeader("Content-Disposition","attachment; filename="+ URLEncoder.encode(fileName, "UTF-8"));
        // 下载文件的输入流
        FileInputStream fileInputStream = new FileInputStream(realPath);
        // 创建缓冲区
        int len=0;
        byte[] buffer = new byte[1024];
        // 获取输出流
        ServletOutputStream outputStream = resp.getOutputStream();
        while ((len=fileInputStream.read(buffer))>0){
            outputStream.write(buffer,0,len);
        }
        fileInputStream.close();


    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}