九、文件上传和下载

1、文件下载

使用ResponseEntity实现下载文件的功能

package com.yzh.controller;

import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.util.MultiValueMap;
import org.springframework.web.bind.annotation.RequestMapping;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpSession;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

@Controller
public class FileController {
    
    @RequestMapping("/testDownload")
    public ResponseEntity<byte[]> testResponseEntity(HttpSession session) throws IOException {
    
        //获取ServletContext对象
        ServletContext servletContext = session.getServletContext();
        //获取服务器中文件的真实路径
        String realPath = servletContext.getRealPath("/static/img/img1.jpg");
        System.out.println(realPath);
        //创建输入流
        InputStream inputStream = new FileInputStream(realPath);
        //创建字节数组
        byte[] bytes = new byte[inputStream.available()];
        //将流读到字节数组中
        inputStream.read(bytes);
        //创建HttpHeaders对象设置响应头信息
        MultiValueMap<String, String> headers = new HttpHeaders();
        //设置要下载方式以及下载文件的名字
        headers.add("Content-Disposition", "attachment;filename=img1.jpg");
        //设置响应状态码
        HttpStatus statusCode = HttpStatus.OK;
        //创建ResponseEntity对象
        ResponseEntity<byte[]> responseEntity = new ResponseEntity<byte[]>(bytes, headers, statusCode);
        //关闭输入流
        inputStream.close();
        return responseEntity;
    }

}

2、文件上传

文件上传要求form表单的请求方式必须为post，并且添加属性enctype=“multipart/form-data”

<form th:action="@{/testUp}" method="post" enctype="multipart/form-data">
    好看图片：<input type="file" name="photo">
    <input type="submit" value="文件上传">
</form>

SpringMVC中将上传的文件封装到MultipartFile对象中，通过此对象可以获取文件相关信息

上传步骤：

a>添加依赖

   <!-- commons-fileupload -->
        <dependency>
            <groupId>commons-fileupload</groupId>
            <artifactId>commons-fileupload</artifactId>
            <version>1.3.1</version>
        </dependency>

b>在SpringMVC的配置文件中添加配置

<!--必须通过文件解析器的解析才能将文件转换为MultipartFile对象-->
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver"></bean>

c>控制器方法

    @RequestMapping("/testUp")
    public String testUp(MultipartFile photo, HttpSession session) throws IOException {
    
        //获取上传的文件的文件名
        String fileName = photo.getOriginalFilename();
        //处理文件重名问题
        String hzName = fileName.substring(fileName.lastIndexOf("."));
        fileName = UUID.randomUUID().toString() + hzName;
        //获取服务器中photo目录的路径
        ServletContext servletContext = session.getServletContext();
        String photoPath = servletContext.getRealPath("photo");
        File file = new File(photoPath);
        if(!file.exists()){
    
            file.mkdir();
        }
        String finalPath = photoPath + File.separator + fileName;
        //实现上传功能
        photo.transferTo(new File(finalPath));
        return "success";
    }