文件上传SpringBoot后端MultipartFile参数报空问题的解决办法

时间：2021-04-25 10:12:39|栏目：JAVA代码|点击：次

最近写了一个文件上传的小demo，就是简单的前端html页面，后端controller接收，但是后端一直报错文件为null，看了很多文章，有说spring-boot自带的org.springframework.web.multipart.MultipartFile和Multipart冲突了，要在启动类中加入@EnableAutoConfiguration(exclue={MultipartAutoConfiguration.class})，有说要在MultipartFile参数前加上@RequestParam(“file”)以表明该参数类型是文件类型，还有说是前端表单没有设置enctype=“multipart/form-data”，参照上面方法我还是没有解决问题，后来更换了spring-boot版本就好了，代码如下：

1、pom.xml(注意我这里用的是2.0.4版本)

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.0.4.RELEASE</version>
  </parent>
  <groupId>org.sang</groupId>
  <artifactId>chapter01</artifactId>
  <version>1.0-SNAPSHOT</version>
  <dependencies>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
  </dependencies>
  <build>
    <plugins>
      <plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
      </plugin>
    </plugins>
  </build>
</project>

2、upload.html页面

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>
<form action="/upload" method="post" enctype="multipart/form-data">
  <input type="file" name="uploadFile" value="请选择文件">
  <input type="submit" value="上传">
</form>
</body>
</html>

3、后端controller

import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;
import javax.servlet.http.HttpServletRequest;
import java.io.File;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.UUID;

@RestController
public class FileUploadController {
  SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/dd");
  @PostMapping("upload")
  public String upload(MultipartFile uploadFile, HttpServletRequest req){
    String realPath = req.getSession().getServletContext().getRealPath("/uploadFile");
    String format = sdf.format(new Date());
    File folder = new File(realPath+format);
    if(!folder.isDirectory()){
      folder.mkdirs();
    }
    String oldName = uploadFile.getOriginalFilename();
    String newName = UUID.randomUUID().toString()+oldName.substring(oldName.lastIndexOf("."),oldName.length());
    try{
      uploadFile.transferTo(new File(folder,newName));
      String path = req.getScheme()+"://"+req.getServerName()+":"+req.getServerPort()+"/uploadFile/"+format+newName;
      return path;
    }catch (IOException e){
      e.printStackTrace();
    }
    return "上传失败";
  }
}

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