目录

• • • • 一、说明
      • 二、四种方式
      • 三、代码示例
      • • 3.1 @Bean方式
        • 3.2 @Bean方式
        • 3.3 @Import导入ImportBeanDefinitionRegistrar实现类
        • 3.4 BeanDefinitionRegistryPostProcessor

一、说明

• 1.第三方的bean不能改写源码，在类上加@Component注解
• 2.只能引入该类进行反射创建，再更改其BeanDefinition信息

二、四种方式

• 1.@Bean方式，实例化过程可以更改
• 2.@Import导入类，实例化过程不能干预
• 3.@Import导入ImportBeanDefinitionRegistrar实现类，可以给BeanDefinition设置属性等信息
• 4.beanDefinition注册后置处理器(BeanDefinitionRegistryPostProcessor)，不需要@Import引入，但顺序在后面

三、代码示例

3.1 @Bean方式

package com.learning.bean;import com.alibaba.druid.pool.DruidDataSource;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;/*** @Author wangyouhui* @Description 配置类**/
@Configuration
public class BeanConfig {@Beanpublic DruidDataSource dataSource(){DruidDataSource dataSource = new DruidDataSource();dataSource.setUsername("root");return dataSource;}
}

3.2 @Bean方式

package com.learning.bean;import com.alibaba.druid.pool.DruidDataSource;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;/*** @Author wangyouhui* @Description 配置类**/
@Configuration
@Import(DruidDataSource.class)
public class BeanConfig2 {
}

3.3 @Import导入ImportBeanDefinitionRegistrar实现类

package com.learning.bean;import com.alibaba.druid.pool.DruidDataSource;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.RootBeanDefinition;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.core.type.AnnotationMetadata;/*** @Author wangyouhui* @Description 配置类**/
@Configuration
@Import(ImportBeanDefinitionRegistrar.class)
public class BeanConfig3 {
}class ImportBeanDefinitionRegistrar implements org.springframework.context.annotation.ImportBeanDefinitionRegistrar{@Overridepublic void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {// BeanDefinition存储Bean的描述信息，决定Bean生产方式RootBeanDefinition rootBeanDefinition = new RootBeanDefinition(DruidDataSource.class);rootBeanDefinition.getPropertyValues().add("password", "root");registry.registerBeanDefinition("dataSource", rootBeanDefinition);}
}

3.4 BeanDefinitionRegistryPostProcessor

package com.learning.bean;import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.RootBeanDefinition;
import org.springframework.stereotype.Component;/*** @Author wangyouhui* @Description beanDefinition注册后置处理器**/
@Component
public class BeanDefinitionRegistryPostProcessor implements org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor {@Overridepublic void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry beanDefinitionRegistry) throws BeansException {RootBeanDefinition beanDefinition = new RootBeanDefinition();beanDefinition.getPropertyValues().add("password", "root");beanDefinitionRegistry.registerBeanDefinition("dataSource", beanDefinition);}@Overridepublic void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {}
}