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| 1 | +### 通过Java配置Bean的几种方式 |
| 2 | + |
| 3 | +#### 1.通过@Configuration注解注入Bean的方式 |
| 4 | + |
| 5 | +```java |
| 6 | +@Configuration |
| 7 | +public class MyBeanConfiguration { |
| 8 | + |
| 9 | + /** |
| 10 | + * 通过 @Configuration注解 注入一个Bean |
| 11 | + */ |
| 12 | + @Bean("dog") |
| 13 | + public Animal getDog() { |
| 14 | + return new Dog(); |
| 15 | + } |
| 16 | + |
| 17 | +} |
| 18 | +``` |
| 19 | + |
| 20 | + |
| 21 | + |
| 22 | +#### 2.通过实现FactoryBean<?>接口的方式注入Bean |
| 23 | + |
| 24 | +```java |
| 25 | +@Component |
| 26 | +public class MyFactoryBean implements FactoryBean<Animal> { |
| 27 | + |
| 28 | + /** |
| 29 | + * 返回要注入的类 |
| 30 | + */ |
| 31 | + @Override |
| 32 | + public Animal getObject() throws Exception { |
| 33 | + return new Cat(); |
| 34 | + } |
| 35 | + |
| 36 | + /** |
| 37 | + * 获取要注入类的类型 |
| 38 | + */ |
| 39 | + @Override |
| 40 | + public Class<?> getObjectType() { |
| 41 | + return Animal.class; |
| 42 | + } |
| 43 | + |
| 44 | + @Override |
| 45 | + public boolean isSingleton() { |
| 46 | + return FactoryBean.super.isSingleton(); |
| 47 | + } |
| 48 | + |
| 49 | +} |
| 50 | +``` |
| 51 | + |
| 52 | + |
| 53 | + |
| 54 | +#### 3.通过实现BeanDefinitionRegistryPostProcessor接口的方式注入Bean |
| 55 | + |
| 56 | +```java |
| 57 | +@Component |
| 58 | +public class MyBeanDefinitionRegistry implements BeanDefinitionRegistryPostProcessor { |
| 59 | + |
| 60 | + /** |
| 61 | + * 通过BeanDefinitionRegistryPostProcessor |
| 62 | + */ |
| 63 | + @Override |
| 64 | + public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry beanDefinitionRegistry) throws BeansException { |
| 65 | + RootBeanDefinition rootBeanDefinition = new RootBeanDefinition(); |
| 66 | + rootBeanDefinition.setBeanClass(Monkey.class); |
| 67 | + beanDefinitionRegistry.registerBeanDefinition("monkey", rootBeanDefinition); |
| 68 | + } |
| 69 | + |
| 70 | + @Override |
| 71 | + public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException { |
| 72 | + |
| 73 | + } |
| 74 | +} |
| 75 | +``` |
| 76 | + |
| 77 | + |
| 78 | + |
| 79 | +#### 4.通过实现ImportBeanDefinitionRegistrar接口的方式注入Bean |
| 80 | + |
| 81 | +```java |
| 82 | +public class MyImportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar { |
| 83 | + |
| 84 | + /** |
| 85 | + * 通过ImportBeanDefinitionRegistrar注入Bean |
| 86 | + */ |
| 87 | + @Override |
| 88 | + public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) { |
| 89 | + RootBeanDefinition rootBeanDefinition = new RootBeanDefinition(); |
| 90 | + rootBeanDefinition.setBeanClass(Bird.class); |
| 91 | + registry.registerBeanDefinition("bird", rootBeanDefinition); |
| 92 | + } |
| 93 | +} |
| 94 | + |
| 95 | +``` |
| 96 | + |
| 97 | +> 使用时:用 @Import(MyImportBeanDefinitionRegistrar.class) 进行注入 |
| 98 | +
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