JavaNote 4.1 Servlet实现下载示例

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本文详细介绍了一个使用Java Servlet实现文件下载的例子。通过设置HTTP响应头来触发浏览器下载功能，而不是预览文件，同时展示了如何读取服务器上的文件并将其发送到客户端。

1、示例

package com.test;


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

@WebServlet(name = "Servlet_5",urlPatterns = "/download")
public class Servlet_5 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取请求参数
        String filename = request.getParameter("filename");
        //获取文件类型
        String mimeType = this.getServletContext().getMimeType(filename);
        //设置响应类型
        response.setContentType(mimeType);
        //设置相应头，如不设置该响应头，凡是能被浏览器识别的如jpg、txt等格式会预览，设置后会直接下载
        response.setHeader("Content-Disposition","attachment;filename=" + filename);
        //获取文件的绝对路劲
        String real = this.getServletContext().getRealPath("download/" + filename);
        InputStream in = new FileInputStream(real);
        ServletOutputStream servletOutputStream = response.getOutputStream();

        int len = 0;
        byte[]buff = new byte[1024];
        while((len = in.read(buff))>0){
            servletOutputStream.write(buff,0,len);
        }
        in.close();

    }

}