【MoodVine】自定义注解@CustomParam

模仿@RequestParam自定义一个注解@CustomParam，实现与@RequestParam同样的功能，只不过@RequestParam注解是从请求路径上获取参数，而我们自定义的@CustomParam注解则是从 request body 中获取参数

第一步，定义注解

@Target(ElementType.PARAMETER)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface CustomParam {

    /**
     * Alias for {@link #name}.
     */
    @AliasFor("name")
    String value() default "";

    /**
     * The name of the request parameter to bind to.
     *
     * @since 4.2
     */
    @AliasFor("value")
    String name() default "";

    /**
     * Whether the parameter is required.
     * <p>Default is {@code true}, leading to an exception thrown in case
     * of the parameter missing in the request. Swit