springBoot上傳文件時MultipartFile報空問題解決方法

1.問題描述:

之前用spring MVC，轉成spring boot之后發現上傳不能用。網上參考說是spring boot已經有CommonsMultipartResolver了，但是我的上傳后台接收的還是null。

2.解決方法

加入配置類

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 {
    //顯示聲明CommonsMultipartResolver為mutipartResolver
    @Bean(name = "multipartResolver")
    public MultipartResolver multipartResolver() {
        CommonsMultipartResolver resolver = new CommonsMultipartResolver();
        resolver.setDefaultEncoding("UTF-8");
        //resolveLazily屬性啟用是為了推遲文件解析，以在在UploadAction中捕獲文件大小異常
        resolver.setResolveLazily(true);
        resolver.setMaxInMemorySize(40960);
        //上傳文件大小 5M 5*1024*1024
        resolver.setMaxUploadSize(5 * 1024 * 1024);
        return resolver;
    }

}

在springboot啟動類上加入注解

//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);
	}
}

特別注意Controller接收的時候一定要加上@RequestParam,否則不可用,如下所示:

@RequestParam("file") MultipartFile multipartFile