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在使用 Spring 框架后，对象以 Bean 的形式统一交给 IOC 容器去创建和管理。现阶段主流的方式是基于 SpringBoot 框架，基于注解的方式实现 Bean 的创建，但在原生 Spring 框架中其实存在三种创建 Bean 的方式。

一、基础类

1. BeanProcess 实体类，虽然加了 @Component 等三个注解，但只在注解方式创建 Bean 时用到了。

package com.nineya.spring.entity;import lombok.Getter;
import lombok.Setter;
import org.springframework.stereotype.Component;import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;@Getter
@Setter
@Component("test")
public class BeanProcess {private String name;@PostConstructpublic void init() {System.out.println("Bean InitMethodName");}@PreDestroypublic void destroy() {System.out.println("Bean DestroyMethodName");}}

2. 后置处理器类

BeanPostProcessor 后置处理器。

package com.nineya.spring.processor;import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.stereotype.Component;@Component
public class NineyaBeanPostProcessor implements BeanPostProcessor {@Overridepublic Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {System.out.println("BeanPostProcessor.postProcessAfterInitialization(" + beanName + ") 后置处理器");return bean;}@Overridepublic Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {System.out.println("BeanPostProcessor.postProcessBeforeInitialization(" + beanName + ") 后置处理器");return bean;}
}

BeanFactoryPostProcessor 后置处理器。

package com.nineya.spring.processor;import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.stereotype.Component;@Component
public class NineyaBeanFactoryPostProcessor implements BeanFactoryPostProcessor {@Overridepublic void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {System.out.println("BeanFactoryPostProcessor.postProcessBeanFactory 后置处理器");}
}

二、三种创建方式

2.1 JavaApi 方式

JavaApi 方式没有注册 BeanFactoryPostProcessor 后置处理器的接口，应该在注册添加完所有 BeanDefinition 后，手动调用执行 BeanFactoryPostProcessor 后置处理器方法。

private static void javaApi() {// 创建bean工厂DefaultListableBeanFactory context = new DefaultListableBeanFactory();//构造bean定义GenericBeanDefinition gbd = new GenericBeanDefinition();gbd.setBeanClass(BeanProcess.class);// 设置属性List<PropertyValue> propertyValues = new ArrayList<>();propertyValues.add(new PropertyValue("name", "test"));gbd.setPropertyValues(new MutablePropertyValues(propertyValues));// 设置生命周期方法gbd.setInitMethodName("init");gbd.setDestroyMethodName("destroy");//注册到环境上下文context.registerBeanDefinition("test", gbd);context.addBeanPostProcessor(new NineyaBeanPostProcessor());new NineyaBeanFactoryPostProcessor().postProcessBeanFactory(context);// 通过class取得beanBeanProcess beanProcess = context.getBean(BeanProcess.class);System.out.println(beanProcess + " : " + beanProcess.hashCode());
}

2.2 xml方式

创建 bean 的 xml 文件。

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsd"><bean class="com.nineya.spring.entity.BeanProcess" name="test" init-method="init" destroy-method="destroy"><property name="name" value="test" /></bean><!-- 注册处理器 --><bean class="com.nineya.spring.processor.NineyaBeanPostProcessor"/><bean class="com.nineya.spring.processor.NineyaBeanFactoryPostProcessor"/>
</beans>

读取 xml 文件创建 bean 工厂。

private static void xmlFile() {ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");// 通过class取得beanBeanProcess beanProcess = context.getBean(BeanProcess.class);System.out.println(beanProcess + " : " + beanProcess.hashCode());
}

2.3 注解方式

private static void annotation() {AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();// 配置注解扫描路径context.scan(BeanLifecycleMain.class.getPackage().getName());context.refresh();// 通过class取得beanBeanProcess beanProcess = context.getBean(BeanProcess.class);System.out.println(beanProcess + " : " + beanProcess.hashCode());
}