查看 RequestParam 源码

java">package org.springframework.web.bind.annotation;import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import org.springframework.core.annotation.AliasFor;@Target({ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RequestParam {@AliasFor("name")String value() default "";@AliasFor("value")String name() default "";boolean required() default true;String defaultValue() default "\n\t\t\n\t\t\n\ue000\ue001\ue002\n\t\t\t\t\n";
}

 可以看到这行

   boolean required() default true;  

代表参数必传

可通过注解参数修改必传属性为 false

@RequestParam(name="file", required = false)