模拟springboot的autoconfigure.condition

说明：模拟一个类存在，这让spring添加user对象的自定义的注解

public class ClassCondition implements Condition {
    
    @Override
    public boolean matches(ConditionContext context, AnnotatedTypemetadata metadata) {

        //需求： 导入通过注解属性值value指定坐标后创建Bean
        //获取注解属性值  value
        Map map = metadata.getAnnotationAttributes(ConditionOnClass.class.getName());
        System.out.println(map);
        String[] value = (String[]) map.get("value");

        boolean flag = true;
        try {
            for (String className : value) {
                Class cls = Class.forName(className);
            }
        } catch (ClassNotFoundException e) {
            flag = false;
        }
        return flag;

    }
}

@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@documented
@Conditional(ClassCondition.class)
public @interface ConditionOnClass {
    String[] value();
}

@Configuration
public class UserConfig {

    @Bean
    @ConditionOnClass("com.zhonglv.mycodition.domain.uesrOn")
    public User user(){
        return new User();
    }

从第三步我们可以看出来  只要com.zhonglv.mycodition.domain.uesrOn这个类存在，则springIoc帮我们创建user对象

@SpringBootApplication
public class MycoditionApplication {

    public static void main(String[] args) {
        ConfigurableApplicationContext run = SpringApplication.run(MycoditionApplication.class, args);
        Object bean = run.getBean("user");
        System.out.println(bean);

    }

}

mycodition · zhonglv/springboot - 码云 - 开源中国 (gitee.com)

//    @Bean
//    @ConditionalOnProperty(name = "zhonglv",havingValue = "yz")
//    public User user2(){
//        return new User();
//    }