Spring boot MultipartResolver

【参考文章】：Required MultipartFile parameter 'file' is not present

【参考文章】：Springboot2.0中WebMvcConfigurerAdapter过时问题处理

【参考文章】：spring boot EnableAutoConfiguration exclude 无效

实现了 MultipartResolver 常用接口有两个：

　　一个是  CommonsMultipartResolver：使用Jakarta Commons FileUpload 解析 multipart 请求；

　　一个是 StandardServletMultipartResolver：依赖于 Servlet 3.0 解析 multipart 请求；

1. StandardServletMultipartResolver 

　　Spring boot 默认使用 StandardServletMultipartResolver 解析 multipart 请求；

@Configuration
@ConditionalOnClass({ Servlet.class, StandardServletMultipartResolver.class,
        MultipartConfigElement.class })
@ConditionalOnProperty(prefix = "spring.servlet.multipart", name = "enabled", matchIfMissing = true)
@ConditionalOnWebApplication(type = Type.SERVLET)
@EnableConfigurationProperties(MultipartProperties.class)
public class MultipartAutoConfiguration {

    private final MultipartProperties multipartProperties;

    public MultipartAutoConfiguration(MultipartProperties multipartProperties) {
        this.multipartProperties = multipartProperties;
    }

    @Bean
    @ConditionalOnMissingBean({ MultipartConfigElement.class,
            CommonsMultipartResolver.class })
    public MultipartConfigElement multipartConfigElement() {
        return this.multipartProperties.createMultipartConfig();
    }

    @Bean(name = DispatcherServlet.MULTIPART_RESOLVER_BEAN_NAME)
    @ConditionalOnMissingBean(MultipartResolver.class)
    public StandardServletMultipartResolver multipartResolver() {
        StandardServletMultipartResolver multipartResolver = new StandardServletMultipartResolver();
        multipartResolver.setResolveLazily(this.multipartProperties.isResolveLazily());
        return multipartResolver;
    }

}

2. CommonsMultipartResolver

2.1 排除默认配置

spring:
  autoconfigure:
    exclude: org.springframework.boot.autoconfigure.web.servlet.MultipartAutoConfiguration

2.2 添加 CommonsMultipartResolver 的依赖

         <!--文件上传-->
        <dependency>
            <groupId>commons-fileupload</groupId>
            <artifactId>commons-fileupload</artifactId>
            <version>1.4</version>
        </dependency>

2.3 创建文件解析对象

@Slf4j
@Configuration
public class  WebMvcConfig implements WebMvcConfigurer {

    @Bean(name = "multipartResolver")
    public MultipartResolver multipartResolver() {
        log.info("Loading the multipart resolver");
        CommonsMultipartResolver multipartResolver = new CommonsMultipartResolver();
        return multipartResolver;
    }
}