springboot⼏种⽂件上传⽅式  基于springboot 2.3.4.RELEASE。 l
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>commons-io</groupId>
<artifactId>commons-io</artifactId>
<version>2.8.0</version>
</dependency>
<dependency>
<groupId>commons-fileupload</groupId>
<artifactId>commons-fileupload</artifactId>
<version>1.4</version>
</dependency>
  提交配置属注意项：1、POST提交； 2、enctype="multipart/form-data"
第⼀种：使⽤spring的 MultipartFile 接⼝来接收
<form action="/file/upload1" method="post" enctype="multipart/form-data">
<input type="file" name="file"/>
<input type="submit" value="上传"/>
</form>
@RequestMapping(value = " file/upload1")
public String  fileUpload1(@RequestParam("file") MultipartFile file) throws IOException {
String path=uploadPath+ File.separator + "upload1" + File.separator +OriginalFilename();
File destination = new File(path);
if (!ParentFile().exists()){
FileUtils.forceMkdirParent(destination); //使⽤commons-io的⼯具类
}
return "success:" + path;
}
  默认⽂件⼤⼩在1MB，可以使⽤配置⽂件l进⾏调节：
spring:
servlet:
multipart:
max-file-size: 10MB  #每个⽂件⼤⼩
max-request-size: 30MB  #请求上传⽂件总量
第⼆种，使⽤具体实现类CommonsMultipartFile。如果参数过多也可以封装成对象进⾏传递
public class UploadParam {
private int tradeDate;
private CommonsMultipartFile file;
//省略set get
}
前端html的写法与第⼀种⽆异。
@RequestMapping("upload2")
public String  fileUpload2(UploadParam param) throws IOException {
String file = uploadPath + File.separator + "upload2" + File.separator + File().getOriginalFilename();
File destination = new File(file);
if (!ParentFile().exists()){
FileUtils.forceMkdirParent(destination);
前端大文件上传解决方案}
return "success: " + file;
}
第三种，多⽂件上传。参数属性名⼀样即可。
public class MultiFileParam {
private int tradeDate;
private List<CommonsMultipartFile> file;
//省略set get
}
@RequestMapping("upload3")
public String  fileUpload3(MultiFileParam param) throws IOException {
String file = uploadPath + File.separator + "upload3" ;
File destination = new File(file);
if (!ists()){
FileUtils.forceMkdirParent(destination);
}
File dest = new File(file + File.separator + f.getOriginalFilename());
try {
} catch (IOException e) {
e.printStackTrace();
}
});
return "success: " + file;
}
<form action="/upload3" method="post" enctype="multipart/form-data">
<input type="file" name="file"/>
<input type="file" name="file"/>
<input type="submit" value="上传"/>
</form>
常见异常及处理：
1、fileupload.impl.FileSizeLimitExceededException: The field file exceeds its maximum permitted size of 1048576 bytes.
超过默认⼤⼩。通过配置⽂件调节即可。
spring.servlet.multipart.max-file-size=30Mb
spring.servlet.multipart.max-request-size=30Mb
2、java.lang.NoClassDefFoundError: org/apache/commons/fileupload/FileUploadException。缺少依赖包
<dependency>
<groupId>commons-fileupload</groupId>
<artifactId>commons-fileupload</artifactId>
<version>1.4</version>
</dependency>
3、'org.springframework.web.multipartmons.CommonsMultipartFile' for property 'file'; nested exception is
java.lang.IllegalStateException: Cannot convert value of type
'org.springframework.web.multipart.support.StandardMultipartHttpServletRequest$StandardMultipartFile' to required type
'org.springframework.web.multipartmons.CommonsMultipartFile' for property 'file': no matching editors or conversion strategy found] 使⽤实现类，必需实例加载
@Bean
public CommonsMultipartResolver multipartResolver(){
CommonsMultipartResolver multipartResolver = new CommonsMultipartResolver();
multipartResolver.setDefaultEncoding("UTF-8");
multipartResolver.setMaxInMemorySize(10*1024*1024);
multipartResolver.setMaxUploadSize(30*1024*1024);
return multipartResolver;
}