下载文件时HttpServletResponse设置响应头的Content-Disposition属性

Content-Disposition属性有两种类型

1. inline ：将文件内容直接显示在页面
2. attachment：弹出对话框让用户下载

弹出对话框下载文件

resp.setHeader("Content-Disposition", "attachment; filename="+fileName);

web.xml

 <?xml version="1.0" encoding="UTF-8"?>
 <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xmlns="http://java.sun.com/xml/ns/javaee"
     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
         http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
     id="WebApp_ID" version="3.0">
   <display-name>DownloadDemo</display-name>
   <welcome-file-list>
     <welcome-file>index.jsp</welcome-file>
   </welcome-file-list>
 
   <servlet>
       <servlet-name>download</servlet-name>
       <servlet-class>com.qf.servlet.DownloadServlet2</servlet-class>
   </servlet>
   <servlet-mapping>
       <servlet-name>download</servlet-name>
       <url-pattern>/download</url-pattern>
   </servlet-mapping>
 </web-app>

servlet类

 public class DownloadServlet2 extends HttpServlet {
 
     @Override
     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         //获取文件在tomcat下的路径
         String path = getServletContext().getRealPath("download/bb.txt");
 
         //让浏览器收到这份资源的时候， 以下载的方式提醒用户，而不是直接展示
         resp.setHeader("Content-Disposition", "attachment; filename=bb.txt");
 
         //转化成输入流
         InputStream is = new FileInputStream(path);
         OutputStream os = resp.getOutputStream();
 
         int len = 0;
         byte[] bts = new byte[1024];
         while ((len = is.read(bts)) != -1) {
             os.write(bts, 0, len);
         }
         os.close();
         is.close();
     }
 
     @Override
     protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         doGet(req, resp);
     }
 }

url：http://localhost:8080/DownloadDemo/download

直接在浏览器页面打开文件

resp.setHeader("Content-Disposition", "inline; filename="+fileName);

修改servlet类

 public class DownloadServlet2 extends HttpServlet {
 
     @Override
     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         //获取文件在tomcat下的路径
         String path = getServletContext().getRealPath("download/bb.txt");
 
         //让浏览器收到这份资源的时候， 以下载的方式提醒用户，而不是直接展示
         resp.setHeader("Content-Disposition", "inline; filename=bb.txt");
 
         //转化成输入流
         InputStream is = new FileInputStream(path);
         OutputStream os = resp.getOutputStream();
 
         int len = 0;
         byte[] bts = new byte[1024];
         while ((len = is.read(bts)) != -1) {
             os.write(bts, 0, len);
         }
         os.close();
         is.close();
     }
 
     @Override
     protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         doGet(req, resp);
     }
 
 }