文件上传和下载

# 文件上传和下载

文件下载
文件上传

# 文件下载

使用ResponseEntity实现下载文件的功能

@RequestMapping("/testDown")
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/1.jpg");
    //创建输入流
    InputStream is = new FileInputStream(realPath);
    //创建字节数组
    byte[] bytes = new byte[is.available()];
    //将流读到字节数组中
    is.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=1.jpg");
    //设置响应状态码
    HttpStatus statusCode = HttpStatus.OK;
    //创建ResponseEntity对象
    ResponseEntity<byte[]> responseEntity = new ResponseEntity<>(bytes, headers, statusCode);
    //关闭输入流
    is.close();
    return responseEntity;
}

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# 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"

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：

<!-- https://mvnrepository.com/artifact/commons-fileupload/commons-fileupload -->
<dependency>
    <groupId>commons-fileupload</groupId>
    <artifactId>commons-fileupload</artifactId>
    <version>1.3.1</version>
</dependency>

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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>

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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";
}

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Click to view the code writen by author

/**
 * @author frx
 * @version 1.0
 * @date 2022/1/22  15:03
 */
@Controller
public class FileUpAndDownController {
    @RequestMapping("/testDown")
    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/1.jpg");
        //创建输入流
        InputStream is = new FileInputStream(realPath);
        //创建字节数组
        byte[] bytes = new byte[is.available()];
        //将流读到字节数组中
        is.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=1.jpg");
        //设置响应状态码
        HttpStatus statusCode = HttpStatus.OK;
        //创建ResponseEntity对象
        ResponseEntity<byte[]> responseEntity = new ResponseEntity<>(bytes, headers, statusCode);
        //关闭输入流
        is.close();
        return responseEntity;
    }
    @RequestMapping("/testUp")
    public String testUp(MultipartFile photo,HttpSession session) throws IOException {
        //获取上传文件的文件名
        String fileName = photo.getOriginalFilename();
        //获取上传的文件的后缀名
        String suffixName=fileName.substring(fileName.lastIndexOf("."));
        //将UUID来作为文件名的结果作为最终的文件名
        String uuid= UUID.randomUUID().toString().replace("-","");
        //将uuid和后缀名拼接后的结果作为最终的文件名
        fileName=uuid+suffixName;
        //通过ServletContext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);
        //判断photoPath所对应路径是否存在
        if(!file.exists()){
            //若不存在，则创建目录
            file.mkdir();
        }
        String finalPath=photoPath+File.separator+ fileName;
        photo.transferTo(new File(finalPath));
        return "success";
    }
}

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<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>测试文件上传和下载</title>
</head>
<body>
<a th:href="@{/testDown}">下载1.jpg</a>
<form th:action="@{/testUp}" method="post" enctype="multipart/form-data">
    头像:<input type="file" name="photo"><br>
    <input type="submit" value="上传">
</form>
</body>
</html>

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<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h1>success</h1>
</body>
</html>

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上次更新: 2024年3月20日

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