Spring Boot @ConditionalOnMissingBean 和泛型类型

使用Spring Boot框架开发应用程序时，经常会遇到需要根据某些条件来决定是否创建某个Bean的情况。Spring Boot提供了一个注解@ConditionalOnMissingBean来实现这一功能。除此之外，还可以结合泛型类型来进一步精确地控制Bean的创建。本文将介绍如何使用@ConditionalOnMissingBean注解和泛型类型来实现条件Bean的创建，并提供相关的案例代码。

java
public interface Animal {
    void eat();
}

java
public class Dog implements Animal {
    @Override
    public void eat() {
        System.out.println("Dog is eating.");
    }
}
public class Cat implements Animal {
    @Override
    public void eat() {
        System.out.println("Cat is eating.");
    }
}

java
@Configuration
public class AnimalConfig {
    @Bean
    @ConditionalOnMissingBean
    public Animal dog() {
        return new Dog();
    }
    @Bean
    @ConditionalOnMissingBean
    public Animal cat() {
        return new Cat();
    }
}

java
@SpringBootTest
public class AnimalConfigTest {
    @Autowired
    private ApplicationContext applicationContext;
    @Test
    public void testBeanCreation() {
        Animal animal = applicationContext.getBean(Animal.class);
        animal.eat();
    }
}

Dog is eating.