SpringMVC:学习笔记(9)——文件下载

时间：2024-05-06 13:03:31

SpringMVC—文件下载

说明

两个案例

　　1.为登录用户提供下载服务。

　　2.阻止仅通过输入网址即可获取下载。

文件下载概览

　　为了将文件发送给浏览器，我们需要在控制器中完成以下操作：

  1. 对请求处理方法使用void返回类型，并且在方法中添加HttpServletResponse参数。
  2. 将响应的内容类型设为文件的内容类型。Content-Type标题在某个实体的body中定义数据的类型，并包含媒体类型和子类型标识符。如果不清楚内容类型，并且希望浏览器失始终显示保存对话框，则将它设为APPLICATION/OCTET-STREAM。这个值时不区分大小写的。
  3. 添加一个名为Content-Disposition的HTTP响应标题，并赋值attachment;filename=fileName，这里的fileName是默认的文件名。

案例1：为登录用户提供下载服务

Domain类

package domain;

public class Login {

    private String username;

    private String password;

    public String getUsername() {

        return username;

    }

    public void setUsername(String username) {

        this.username = username;

    }

    public String getPassword() {

        return password;

    }

    public void setPassword(String password) {

        this.password = password;

    }

}

Controller控制器

package controller;

import domain.Login;

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

import org.springframework.stereotype.Controller;

import org.springframework.ui.Model;

import org.springframework.web.bind.annotation.ModelAttribute;

import org.springframework.web.bind.annotation.RequestMapping;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

import java.io.*;

@Controller

public class ResourceController {

    private static final Log logger = LogFactory.getLog(ResourceController.class);

    @RequestMapping(value = "/login")

    public String login(@ModelAttribute Login login, HttpSession session, Model model)

    {

        model.addAttribute("login",new Login());

        if("ms".equals(login.getUsername())&&"123".equals(login.getPassword()))

        {

            session.setAttribute("loggedIn",Boolean.TRUE);

            return "Main";

        }

        else

        {

            return "LoginForm";

        }

    }

    @RequestMapping(value = "/resource_download")

    public String downloadResource(HttpSession session, HttpServletRequest request, HttpServletResponse response)

    {

        if(session==null||session.getAttribute("loggedIn")==null)

        {

        return "LoginForm";

        }

        String dataDirectory = request.getServletContext().getRealPath("/WEB-INF/data");

        File file = new File(dataDirectory,"Blog.zip");

        if(file.exists())

        {

            response.setContentType("application/octet-stream");

            response.addHeader("Content-Disposition","attachment;filename=Blog.zip");

            byte[] buffer = new byte[1024];

            FileInputStream fis =null;

            BufferedInputStream bis =null;

            try {

                fis = new FileInputStream(file);

                bis = new BufferedInputStream(fis);

                OutputStream os =response.getOutputStream();

                int i =bis.read(buffer);

                while (i!=-1) {

                    os.write(buffer, 0, i);

                    i=bis.read(buffer);

                }

            } catch (FileNotFoundException e) {

                e.printStackTrace();

            } catch (IOException e) {

                e.printStackTrace();

            }finally {

                try {

                    bis.close();

                } catch (IOException e) {

                    e.printStackTrace();

                }

                try {

                    fis.close();

                } catch (IOException e) {

                    e.printStackTrace();

                }

            }

        }

        return null;

    }

}

编写视图

Main.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

<html>

<head>

    <title>DownPage</title>

</head>

<body>

    <h4>点击链接下载文件</h4>

    <p>

        <a href="resource_download" >Down</a>

    </p>

</body>

</html>

LoginForm.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

<html>

<head>

    <title>登录页面</title>

</head>

<body>

    <form:form commandName="login" action="login" method="post">

        账号: <br>

        <form:input path="username" cssErrorClass="error" id="username"/>

        <br> 密码： <br>

        <form:input path="password" cssErrorClass="error" id="password"/>

        <br> <input type="submit" value="提交">

    </form:form>

</body>

</html>

案例2：阻止仅通过输入网址即可获取下载

    @RequestMapping(value = "/resource_download")

    public String downloadResource(HttpSession session, HttpServletRequest request, HttpServletResponse response,@RequestHeader String refuer

    ){
if(refer==null) //通过判断refer来浏览器输入网址就能下载图片的情况

        {

        　　return "LoginForm";

        }

        String dataDirectory = request.getServletContext().getRealPath("/WEB-INF/data");

        File file = new File(dataDirectory,"Blog.zip");

        if(file.exists())

        {

            response.setContentType("application/octet-stream");

            response.addHeader("Content-Disposition","attachment;filename=Blog.zip");

            byte[] buffer = new byte[1024];

            FileInputStream fis =null;

            BufferedInputStream bis =null;

            try {

                fis = new FileInputStream(file);

                bis = new BufferedInputStream(fis);

                OutputStream os =response.getOutputStream();

                int i =bis.read(buffer);

                while (i!=-1) {

                    os.write(buffer, 0, i);

                    i=bis.read(buffer);

                }

            } catch (FileNotFoundException e) {

                e.printStackTrace();

            } catch (IOException e) {

                e.printStackTrace();

            }finally {

                try {

                    bis.close();

                } catch (IOException e) {

                    e.printStackTrace();

                }

                try {

                    fis.close();

                } catch (IOException e) {

                    e.printStackTrace();

                }

            }

        }

        return null;

    }

}

　　

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