@Conditional注解: 条件，注解内的条件满足才会创建这个类

@Conditional(MyCondition.class) @Bean public String example() { return “example”; }

class MyCondition implements Condition { public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) { … } }

@ConditionalOnClass注解: classpath里存在这个类才去解析配置类

@ConditionalOnMissingClsss