Spring实践手动注册Bean的几种方式

Z时代
2024-01-10
分类：综合

第一种(ClassPathXmlApplicationContext)

1.此种方式使用传统xml方式启动spring容器(xml里面没有任何配置)

public static void main(String[] args) {
       ClassPathXmlApplicationContext context = new     
      ClassPathXmlApplicationContext("spring/spring.xml");
       // 获取spring bean 工厂 手动注册bean
       context.getBeanFactory().registerSingleton("helloWord", new HelloWord());
       // 启动spring容器
       context.start();
       // 从上下文获取bean
       HelloWord helloWord = context.getBean("helloWord", HelloWord.class);
       System.out.println(helloWord.say());
   }

xml内容

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd">
</beans>

第二种(AnnotationConfigApplicationContext)

/** 方法二：AnnotationConfigApplicationContext(Bootstrap.class) **/
AnnotationConfigApplicationContext applicationContext1 = new AnnotationConfigApplicationContext(Bootstrap.class);
DefaultListableBeanFactory beanFactory = (DefaultListableBeanFactory) applicationContext1.getBeanFactory();

第三种：继承BeanDefinitionRegistryPostProcessor

1.创建一个DefinitionRegistryPostProcessor

/**
@Configuration
或
@Component
或
@Bean定义
**/
@Configuration
public class DefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {
    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory arg0) 
throws BeansException {
    }
    /**
     * 先执行postProcessBeanDefinitionRegistry方法
     * 在执行postProcessBeanFactory方法
     */
    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) 
        throws BeansException {
        // 第一种 ： 手动注入
        // 注册bean
        registerBean(registry, "hello", HelloWord.class);
        registerBean(registry, "helloWord", HelloWord.class);
    }
/**
注册bean
**/
 private void registerBean(BeanDefinitionRegistry registry, String name, Class<?> beanClass) {
        RootBeanDefinition bean = new RootBeanDefinition(beanClass);
        registry.registerBeanDefinition(name, bean);
    }
}

2.测试能否在spring上下文获取该bean

@SpringBoot" title="SpringBoot">SpringBootApplication
public class ApplicationBoot {
    public static void main(String[] args) {
        ApplicationContext applicationContext = SpringApplication.run(ApplicationBoot.class);
        HelloWord helloWord = applicationContext.getBean("hello", HelloWord.class);
        System.out.println(helloWord.say());
    }

第四种：继承ApplicationContextAware

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.ConfigurableApplicationContext;
public class SpringContextUtils implements ApplicationContextAware {
    @Override
    public void setApplicationContext(ApplicationContext applicationContext)
            throws BeansException {
    	/** 方法一：继承ApplicationContextAware：获得applicationContext **/
		// 将applicationContext转换为ConfigurableApplicationContext
		ConfigurableApplicationContext configurableApplicationContext = (ConfigurableApplicationContext) applicationContext;
		// 获取bean工厂并转换为DefaultListableBeanFactory
		DefaultListableBeanFactory defaultListableBeanFactory = (DefaultListableBeanFactory) configurableApplicationContext.getBeanFactory();
		//defaultListableBeanFactory.registerBeanDefinition(beanName, beanDefinition);
    }}