Bean 的实例化方式

「爱情、让人受尽委屈。」 2022-10-31 05:25 173阅读 0赞

Bean 的实例化方式

*  构造方法
 *  静态工厂
 *  Bean 工厂
 *  FactoryBean
 *  SPI，org.springframework.beans.factory.serviceloader.ServiceLoaderFactoryBean
 *  AutowireCapableBeanFactory\#createBean
 *  BeanDefinitionRegistry\#registerBeanDefinition

...

xml 方式，演示实例化方式

spring 配置文件

<?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/beans
                               http://www.springframework.org/schema/beans/spring-beans.xsd">
    
    	
        <bean id="user1" class="constxiong.User">
        	<constructor-arg name="id" value="1"></constructor-arg>
        	<constructor-arg name="name" value="constructor"></constructor-arg>
        </bean>
        
        
        <bean id="user3" class="constxiong.User" factory-method="getUser"></bean>
        
        
        <bean id="user2" factory-bean="userFactory" factory-method="getUser"></bean>
        <bean id="userFactory" class="constxiong.UserFactory"></bean>
        
        
        <bean id="user4" class="constxiong.UserFactoryBean"></bean>
        
        
        <bean id="userFactoryServiceLoader" class="org.springframework.beans.factory.serviceloader.ServiceLoaderFactoryBean">
            <property name="serviceType" value="constxiong.UserFactoryInterface" />
        </bean>
    
    </beans>

constxiong.UserFactoryInterface 文件放在 META-INF/services/ 目录下

constxiong.UserFactoryImpl

测试类：

package constxiong;
    
    import java.util.ServiceLoader;
    
    import org.springframework.beans.factory.config.AutowireCapableBeanFactory;
    import org.springframework.beans.factory.support.BeanDefinitionBuilder;
    import org.springframework.beans.factory.support.DefaultListableBeanFactory;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    /**
     * 测试 Bean 的实例化
     * @author ConstXiong
     */
    public class Test {
    	
    	public static void main(String[] args) {
    		ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("META-INF/spring-bean-instantiation.xml");
    		User user1 = context.getBean("user1", User.class);
    		System.out.println(user1);
    		
    		User user2 = context.getBean("user2", User.class);
    		System.out.println(user2);
    		
    		User user3 = context.getBean("user3", User.class);
    		System.out.println(user3);
    		
    		User user4 = context.getBean("user4", User.class);
    		System.out.println(user4);
    		
    		User user5 = (User) context.getBeanFactory().createBean(User.class, AutowireCapableBeanFactory.AUTOWIRE_NO, false);
    		System.out.println(user5);
    		
    		// BeanDefinition
    		((DefaultListableBeanFactory)context.getBeanFactory()).registerBeanDefinition("user6", BeanDefinitionBuilder.rootBeanDefinition(User.class).addPropertyValue("name", "BeanDefinition").getBeanDefinition());
    		System.out.println(context.getBean("user6", User.class));
    		
    		// spi 方式
    		ServiceLoader<UserFactoryInterface> serviceLoader = context.getBean("userFactoryServiceLoader", ServiceLoader.class);
    		System.out.println(serviceLoader.iterator().next().getUser());
    		// spi JDK 原生代码
    		ServiceLoader<UserFactoryInterface> loader = ServiceLoader.load(UserFactoryInterface.class, Thread.currentThread().getContextClassLoader());
    		System.out.println(loader.iterator().next().getUser());
    	}
    
    }

[完整代码：007-spring-bean-intantiation][007-spring-bean-intantiation]

--------------------

### 【Java学习资源】整理推荐 ###

*  [Bean 的作用域][Bean]
 *  [maven 集成 tomcat 以 jar 的方式打包 web 应用][maven _ tomcat _ jar _ web]
 *  [Spring 依赖注入与依赖查找来源的区别][Spring]
 *  [Spring 依赖注入的处理过程与 DependencyDescriptor 的说明][Spring _ DependencyDescriptor]
 *  [Spring 各种 Aware 接口回调注入][Spring _ Aware]
 *  [Spring Bean 生命周期内的 Exception 复现][Spring Bean _ Exception]
 *  [Spring 内建 Bean][Spring _ Bean]
 *  [Spring Bean 的别名][Spring Bean]
 *  [Spring Bean 未指定名称的命名规则][Spring Bean 1]
 *  [Bean 何时被 GC][Bean _ GC]
 *  [Spring Bean 延迟加载][Spring Bean 2]
 *  [ObjectFactory 与 BeanFactory 的区别][ObjectFactory _ BeanFactory]
 *  [Bean 销毁的方式与顺序][Bean 1]
 *  [Bean 初始化的方式与顺序][Bean 2]
 *  [Bean 的实例化方式][Bean 3]
 *  [Bean的注册方式][Bean 4]
 *  [什么是 BeanDefinition？][BeanDefinition]
 *  [Spring IoC 容器启动时做了什么？][Spring IoC]
 *  [BeanFactory 与 FactoryBean 的区别][BeanFactory _ FactoryBean]
 *  [BeanFactory 与 ApplicationContext 的区别][BeanFactory _ ApplicationContext]
 *  [Spring IoC 依赖注入的实现方式][Spring IoC 1]
 *  [Spring IoC 依赖注入(支持哪些数据类型？)][Spring IoC 2]
 *  [Spring bean 依赖查找][Spring bean]
 *  [Spring-IoC][]
 *  [Spring 的核心特性][Spring 1]

--------------------

### 【Java面试题与答案】整理推荐 ###

*  [基础与语法][Link 1]
 *  [集合][Link 2]
 *  [网络编程][Link 3]
 *  [并发编程][Link 4]
 *  [Web][]
 *  [安全][Link 5]
 *  [设计模式][Link 6]
 *  [框架][Link 7]
 *  [算法与数据结构][Link 8]
 *  [异常][Link 9]
 *  [文件解析与生成][Link 10]
 *  [Linux][]
 *  [MySQL][]
 *  [Oracle][]
 *  [Redis][]
 *  [Dubbo][]

[007-spring-bean-intantiation]: https://github.com/ConstXiong/toy/tree/master/spring-study/007-spring-bean-intantiation
[Bean]: https://www.javanav.com/val/59101a7207864f4aa971e5c48b592c77.html
[maven _ tomcat _ jar _ web]: https://www.javanav.com/val/b1f4691bd6ba488a80e3bdfcefdec33c.html
[Spring]: https://www.javanav.com/val/a9569837e1bc4df9aeac0e6cbf96bf06.html
[Spring _ DependencyDescriptor]: https://www.javanav.com/val/152161d266a94fd38efb365a78d8f9a3.html
[Spring _ Aware]: https://www.javanav.com/val/089b3993c8bc4dec891ea677c104c5e4.html
[Spring Bean _ Exception]: https://www.javanav.com/val/2b31b7061b3342c0a67f8d7fc7373ed3.html
[Spring _ Bean]: https://www.javanav.com/val/92f9e0951b19454196b645bb3cb1a0b9.html
[Spring Bean]: https://www.javanav.com/val/4d39ffc772184e10827d741b1b5ba787.html
[Spring Bean 1]: https://www.javanav.com/val/76a8f38c9f5f42ce8487ad490b41223b.html
[Bean _ GC]: https://www.javanav.com/val/ca4a8f696ee5440bb5d87d3397b59004.html
[Spring Bean 2]: https://www.javanav.com/val/b197550be7ba4bd8b4d82f6835d1abb1.html
[ObjectFactory _ BeanFactory]: https://www.javanav.com/val/016d62d99b0148feaf13529a841f4e46.html
[Bean 1]: https://www.javanav.com/val/a5a7f97894f9499b90e27dbd98124a1c.html
[Bean 2]: https://www.javanav.com/val/cd53474ce0ca4b85ad3c9cf4ed35c13a.html
[Bean 3]: https://www.javanav.com/val/2a6dbdb701804b15a216d409abe83b6b.html
[Bean 4]: https://www.javanav.com/val/a5f8bf440848487bb0c0bdaa6c846cc6.html
[BeanDefinition]: https://www.javanav.com/val/e82279480ec24184bcaf723a50ef08b3.html
[Spring IoC]: https://www.javanav.com/val/d382c8380fc2480788a35a7e671b5e9b.html
[BeanFactory _ FactoryBean]: https://www.javanav.com/val/173e873a2c98499a8a08a13b4f88ae10.html
[BeanFactory _ ApplicationContext]: https://www.javanav.com/val/bbc2c9580b7045e583855925d5f1a50b.html
[Spring IoC 1]: https://www.javanav.com/val/a835e6c709ea439ebb21a80f1bf77926.html
[Spring IoC 2]: https://www.javanav.com/val/e377beac22644c2c85308079b239a0fd.html
[Spring bean]: https://www.javanav.com/val/7f8c2e1f24db46e79bc4b9b04f9ad715.html
[Spring-IoC]: https://www.javanav.com/val/a412668efda74412a13f6df9a6d2c714.html
[Spring 1]: https://www.javanav.com/val/6eac12a548ea40c68ff64b1af307563a.html
[Link 1]: https://www.javanav.com/interview/93b0069472fd479393006c0e73043fc4.html
[Link 2]: https://www.javanav.com/interview/4147d95e693945e7a50345fd33ec817e.html
[Link 3]: https://www.javanav.com/interview/68a57ffc78de4133bb890bdd502ac418.html
[Link 4]: https://www.javanav.com/interview/36a24fa3258e45c89873f474ce914912.html
[Web]: https://www.javanav.com/interview/4e27cb63adb440c6825a159d35cf4010.html
[Link 5]: https://www.javanav.com/interview/03affb2ce3f04fda8853f714e5764906.html
[Link 6]: https://www.javanav.com/interview/07a32a9ff17a4006a53550ce658cafed.html
[Link 7]: https://www.javanav.com/interview/5c466456e9b54ab0a749b5948e51f1d3.html
[Link 8]: https://www.javanav.com/interview/943f917041ee4f05add24539f5b861b2.html
[Link 9]: https://www.javanav.com/interview/d3f058cfc05d4c6dadd821b622e84d36.html
[Link 10]: https://www.javanav.com/interview/67a50996c28f418e83b109ea42fc3eff.html
[Linux]: https://www.javanav.com/interview/00cccb81729540d1923bd0a0ef49533a.html
[MySQL]: https://www.javanav.com/interview/d311e78502a845f1a4bb307bd6aec2b3.html
[Oracle]: https://www.javanav.com/interview/5f29e9677edf4a16be3dce30d257c9ab.html
[Redis]: https://www.javanav.com/interview/066c62b3af4d4827b2243a822c3084a9.html
[Dubbo]: https://www.javanav.com/interview/9a3e7a7740324757abaab953f7ebc455.html