黑马day15 文件下载

1.文件下载..

response.setHeader("Content-Disposition", "attachment;filename="+URLEncoder.encode(filename,"utf-8")); 通知浏览器以下载的方式打开文件...

response.setContentType(this.getServletContext().getMimeType(filename));//通知浏览器下载的MIME类型

2.文件下载的servlet

package cn.itheima.download;

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

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import cn.itheima.utils.IOUtils;

public class DownLoadServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		//1.获取要下载的文件
		String filename = request.getParameter("file");
		response.setHeader("Content-Disposition", "attachment;filename="+URLEncoder.encode(filename,"utf-8"));//告知浏览器要以下载的方式打开...而不是直接打开
		response.setContentType("");//告知浏览器文件的类型
		InputStream in=new FileInputStream(this.getServletContext().getRealPath(filename));
		OutputStream out=response.getOutputStream();
		IOUtils.In2Out(in, out);
		IOUtils.closeIO(in, null);
		
	}

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

}

2.工具类IOUtils

提供了两个方法一个是读取in中的流中的数据写到out流中

另一个是关闭资源流的函数、

package cn.itheima.utils;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class IOUtils {
	private IOUtils(){
		
	}
	/**
	 * 读取流中的数据写到输出流中
	 * @param in
	 * @param out
	 * @throws IOException
	 */
	public static void In2Out(InputStream in,OutputStream out) throws IOException{
		int len=0;
		byte b[]=new byte[1024];
		while((len=in.read(b))!=-1){
			out.write(b, 0, len);
		}
	}
	/**
	 * 关闭资源
	 * @param in
	 * @param out
	 */
	public  static void closeIO(InputStream in,OutputStream out){
		if(in!=null){
			try {
				in.close();
			} catch (IOException e) {
				e.printStackTrace();
			}finally{
				in=null;
			}
		}
		if(out!=null){
			try {
				out.close();
			} catch (IOException e) {
				e.printStackTrace();
			}finally{
				out=null;
			}
		}
	}
}