org.springframework.web.method.ControllerAdviceBean#isApplicableToBeanType 作用

org.springframework.web.method.ControllerAdviceBean#isApplicableToBeanType(@Nullable Class<?> beanType)

判断当前类是否被ControllerAdviceBean修饰，判断依据位 ControllerAdviceBean上设置的注解@ControllerAdvice内的参数

package org.springframework.web.bind.annotation;

import java.lang.annotation.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;
import org.springframework.stereotype.Component;

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface ControllerAdvice {

	@AliasFor("basePackages")
	String[] value() default {};

	@AliasFor("value")
	String[] basePackages() default {};

	Class<?>[] basePackageClasses() default {};

	Class<?>[] assignableTypes() default {};

	Class<? extends Annotation>[] annotations() default {};
}

其内部使用 HandlerTypePredicate beanTypePredicate 进行判断，如果@ControllerAdvice注解内无参数 则可以修饰所有类。

由该段代码判断：

ControllerAdvice annotation = (beanType != null ?
		AnnotatedElementUtils.findMergedAnnotation(beanType, ControllerAdvice.class) : null);

if (annotation != null) {
	this.beanTypePredicate = HandlerTypePredicate.builder()
			.basePackage(annotation.basePackages())
			.basePackageClass(annotation.basePackageClasses())
			.assignableType(annotation.assignableTypes())
			.annotation(annotation.annotations())
			.build();
}
else {
	this.beanTypePredicate = HandlerTypePredicate.forAnyHandlerType();
}

HandlerTypePredicate.forAnyHandlerType(); 改方法实现如下：

return new HandlerTypePredicate(Collections.emptySet(), Collections.emptyList(), Collections.emptyList());

=====

实际会调用org.springframework.web.method.HandlerTypePredicate#test

if (!hasSelectors()) {
   return true;
}

org.springframework.web.method.HandlerTypePredicate#hasSelectors

private boolean hasSelectors() {
   return (!this.basePackages.isEmpty() || !this.assignableTypes.isEmpty() || !this.annotations.isEmpty());
}