springBoot上传文件时MultipartFile报空问题解决方法

1.问题描述:

之前用spring MVC，转成spring boot之后发现上传不能用。网上参考说是spring boot已经有CommonsMultipartResolver了，但是我的上传后台接收的还是null。

2.解决方法

加入配置类

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.multipart.MultipartResolver;
import org.springframework.web.multipart.commons.CommonsMultipartResolver;


@Configuration
public class UploadConfig {
    //显示声明CommonsMultipartResolver为mutipartResolver
    @Bean(name = "multipartResolver")
    public MultipartResolver multipartResolver() {
        CommonsMultipartResolver resolver = new CommonsMultipartResolver();
        resolver.setDefaultEncoding("UTF-8");
        //resolveLazily属性启用是为了推迟文件解析，以在在UploadAction中捕获文件大小异常
        resolver.setResolveLazily(true);
        resolver.setMaxInMemorySize(40960);
        //上传文件大小 5M 5*1024*1024
        resolver.setMaxUploadSize(5 * 1024 * 1024);
        return resolver;
    }

}

在springboot启动类上加入注解

//排除原有的Multipart配置
@EnableAutoConfiguration(exclude = {MultipartAutoConfiguration.class})
public class Application extends SpringBootServletInitializer {
	public static void main(String[] args) {
		SpringApplication.run(Application.class, args);
	}
}

特别注意Controller接收的时候一定要加上@RequestParam,否则不可用,如下所示:

@RequestParam("file") MultipartFile multipartFile