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);
    }
    
}