解决MultipartFile.transferTo(dest) 报FileNotFoundExcep的问题

这篇文章主要介绍了解决MultipartFile.transferTo(dest) 报FileNotFoundExcep的问题，具有很好的参考价值，希望对大家有所帮助。如有错误或未考虑完全的地方，望不吝赐教

Spring Upload file 报错FileNotFoundException

环境：

Springboot 2.0.4
JDK8
内嵌 Apache Tomcat/8.5.32

表单，enctype 和 input 的type=file 即可，例子使用单文件上传

<form enctype="multipart/form-data" method="POST"
 action="/file/fileUpload">
 图片<input type="file" name="file" />
 <input type="submit" value="上传" />
</form>

@Controller
@RequestMapping("/file")
public class UploadFileController {
    @Value("${file.upload.path}")
    private String path = "upload/";
 
    @RequestMapping(value = "fileUpload", method = RequestMethod.POST)
    @ResponseBody
    public String fileUpload(@RequestParam("file") MultipartFile file) {
        if (file.isEmpty()) {
            return "false";
        }
        String fileName = file.getOriginalFilename();
        File dest = new File(path + "/" + fileName);
        if (!dest.getParentFile().exists()) { 
            dest.getParentFile().mkdirs();
        }
        try {
            file.transferTo(dest); // 保存文件
            return "true";
        } catch (Exception e) {
            e.printStackTrace();
            return "false";
        }
    }
}

运行在保存文件 file.transferTo(dest) 报错

问题

dest 是相对路径，指向 upload/doc20170816162034_001.jpg

file.transferTo 方法调用时，判断如果是相对路径，则使用temp目录，为父目录

因此，实际保存位置为 C:\Users\xxxx\AppData\Local\Temp\tomcat.372873030384525225.8080\work\Tomcat\localhost\ROOT\upload\doc20170816162034_001.jpg

一则，位置不对，二则没有父目录存在，因此产生上述错误。

解决办法

transferTo 传入参数定义为绝对路径

@Controller
@RequestMapping("/file")
public class UploadFileController {
    @Value("${file.upload.path}")
    private String path = "upload/";
 
    @RequestMapping(value = "fileUpload", method = RequestMethod.POST)
    @ResponseBody
    public String fileUpload(@RequestParam("file") MultipartFile file) {
        if (file.isEmpty()) {
            return "false";
        }
        String fileName = file.getOriginalFilename();
        File dest = new File(new File(path).getAbsolutePath()+ "/" + fileName);
        if (!dest.getParentFile().exists()) { 
            dest.getParentFile().mkdirs();
        }
        try {
            file.transferTo(dest); // 保存文件
            return "true";
        } catch (Exception e) {
            e.printStackTrace();
            return "false";
        }
    }
}

另外也可以 file.getBytes() 获得字节数组，OutputStream.write(byte[] bytes)自己写到输出流中。

补充方法

application.properties 中增加配置项

spring.servlet.multipart.location= # Intermediate location of uploaded files.

关于上传文件的访问

1、增加一个自定义的ResourceHandler把目录公布出去

// 写一个Java Config 
@Configuration
public class webMvcConfig implements org.springframework.web.servlet.config.annotation.WebMvcConfigurer{
    // 定义在application.properties
    @Value("${file.upload.path}")
    private String path = "upload/";
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        String p = new File(path).getAbsolutePath() + File.separator;//取得在服务器中的绝对路径
        System.out.println("Mapping /upload/** from " + p);
        registry.addResourceHandler("/upload/**") // 外部访问地址
            .addResourceLocations("file:" + p)// springboot需要增加file协议前缀
            .setCacheControl(CacheControl.maxAge(30, TimeUnit.MINUTES));// 设置浏览器缓存30分钟
    }
}
 
 

application.properties 中 file.upload.path=upload/

实际存储目录

D:/upload/2019/03081625111.jpg

访问地址（假设应用发布在http://www.a.com/）

http://www.a.com/upload/2019/03081625111.jpg

2、在Controller中增加一个RequestMapping，把文件输出到输出流中

@RestController
@RequestMapping("/file")
public class UploadFileController {
    @Autowired
    protected HttpServletRequest request;
    @Autowired
    protected HttpServletResponse response;
    @Autowired
    protected ConversionService conversionService;
 
    @Value("${file.upload.path}")
    private String path = "upload/";    
 
    @RequestMapping(value="/view", method = RequestMethod.GET)
    public Object view(@RequestParam("id") Integer id){
        // 通常上传的文件会有一个数据表来存储，这里返回的id是记录id
        UploadFile file = conversionService.convert(id, UploadFile.class);// 这步也可以写在请求参数中
        if(file==null){
            throw new RuntimeException("没有文件");
        }
         
        File source= new File(new File(path).getAbsolutePath()+ "/" + file.getPath());
        response.setContentType(contentType);
 
        try {
            FileCopyUtils.copy(new FileInputStream(source), response.getOutputStream());
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }
}

MultipartFile.transferTo(dest) 报找不到文件

今天使用transferTo这个方法进行上传文件的使用发现了一些路径的一些问题，查找了一下记录问题所在

前端上传网页，使用的是单文件上传的方式

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
</head>
<body>
    <form enctype="multipart/form-data" method="post" action="/upload">
        文件：<input type="file" name="head_img">
        姓名：<input type="text" name="name">
        <input type="submit" value="上传">
    </form>
</body>
</html>

后台网页

@Controller
@RequestMapping("/file")
public class UploadFileController {
    @Value("${file.upload.path}")
    private String path = "upload/";
    @RequestMapping(value = "fileUpload", method = RequestMethod.POST)
    @ResponseBody
    public String fileUpload(@RequestParam("file") MultipartFile file) {
        if (file.isEmpty()) {
            return "false";
        }
        String fileName = file.getOriginalFilename();
        File dest = new File(path + "/" + fileName);
        if (!dest.getParentFile().exists()) { 
            dest.getParentFile().mkdirs();
        }
        try {
            file.transferTo(dest); // 保存文件
            return "true";
        } catch (Exception e) {
            e.printStackTrace();
            return "false";
        }
    }
}

这个确实存在一些问题

路径是不对的