beanDefinition加载bean的三种方式

最新推荐文章于 2023-08-06 13:38:22 发布

原创最新推荐文章于 2023-08-06 13:38:22 发布 · 309 阅读

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#java #spring #开发语言

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该博客详细介绍了如何在 Spring 中从 XML、配置类及通过包扫描获取 BeanDefinition。内容包括使用 DefaultListableBeanFactory、XmlBeanDefinitionReader、ConfigurationClassPostProcessor 和 ClassPathBeanDefinitionScanner 实例化和注册 Bean。

package oilprice;

import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.beans.factory.xml.XmlBeanDefinitionReader;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ClassPathBeanDefinitionScanner;
import org.springframework.context.annotation.ConfigurationClassPostProcessor;
import org.springframework.core.io.ClassPathResource;

import java.util.Arrays;

/**
 * @author micro.cloud.fly
 * @date 2022/7/15 3:39 下午
 * @desc
 */
//演示各种BeanDefinition的来源
public class TestBeanDefinition {
    public static void main(String[] args) {
        System.out.println("========================>一开始");
        DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();
        System.out.println(Arrays.toString(beanFactory.getBeanDefinitionNames()));

        System.out.println("========================>1)从xml 获取");
        XmlBeanDefinitionReader reader1 = new XmlBeanDefinitionReader(beanFactory);
        reader1.loadBeanDefinitions(new ClassPathResource("bd.xml"));
        System.out.println(Arrays.toString(beanFactory.getBeanDefinitionNames()));

        System.out.println("========================> 2)从配置类获取");
        beanFactory.registerBeanDefinition("config1", BeanDefinitionBuilder.genericBeanDefinition(Config1.class).getBeanDefinition());
        ConfigurationClassPostProcessor postProcessor = new ConfigurationClassPostProcessor();
        postProcessor.postProcessBeanDefinitionRegistry(beanFactory);
        System.out.println(Arrays.toString(beanFactory.getBeanDefinitionNames()));

        System.out.println("========================>)扫描获取");
        ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(beanFactory);
        scanner.scan("oilprice.sub");
        //会多出来一些spring内置的一些类，是因为包扫描的过程中，spring内部注册的bean
        System.out.println(Arrays.toString(beanFactory.getBeanDefinitionNames()));


    }

    class Bean1 {

    }

    class Bean2 {

    }

    class Config1 {
        @Bean
        public Bean2 bean2() {
            return new Bean2();
        }
    }
}

bd.xml

<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">


    <bean id="bean1" class="oilprice.TestBeanDefinition$Bean1"/>

</beans>

Bean3.java

package oilprice.sub;

import org.springframework.stereotype.Component;

/**
 * @author micro.cloud.fly
 * @date 2022/7/15 3:49 下午
 * @desc
 */

@Component
public class Bean3 {
}