三万字盘点Spring/Boot的那些常用扩展点（上篇）

// 火灾事件
public class FireEvent extends ApplicationEvent {

    public FireEvent(String source){
        super(source);
    }

}

public class Call119FireEventListener implements ApplicationListener<FireEvent> {

    @Override
    public void onApplicationEvent(FireEvent event){
        System.out.println("打119");
    }

}

public class SavePersonFireEventListener implements ApplicationListener<FireEvent> {

    @Override
    public void onApplicationEvent(FireEvent event){
        System.out.println("救人");
    }

}

public class Application {

    public static void main(String[] args){
        AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext();
        //将 事件监听器 注册到容器中
        applicationContext.register(Call119FireEventListener.class);
        applicationContext.register(SavePersonFireEventListener.class);
        applicationContext.refresh();

        // 发布着火的事件，触发监听
        applicationContext.publishEvent(new FireEvent("着火了"));
    }

}

打119
救人

public class EventPropagateApplication {

    public static void main(String[] args){

        // 创建一个父容器
        AnnotationConfigApplicationContext parentApplicationContext = new AnnotationConfigApplicationContext();
        //将 打119监听器 注册到父容器中
        parentApplicationContext.register(Call119FireEventListener.class);
        parentApplicationContext.refresh();

        // 创建一个子容器
        AnnotationConfigApplicationContext childApplicationContext = new AnnotationConfigApplicationContext();
        //将 救人监听器 注册到子容器中
        childApplicationContext.register(SavePersonFireEventListener.class);
        childApplicationContext.refresh();

        // 设置一下父容器
        childApplicationContext.setParent(parentApplicationContext);

        // 通过子容器发布着火的事件，触发监听
        childApplicationContext.publishEvent(new FireEvent("着火了"));

    }

}

救人
打119

public class SqlSessionFactoryBean
    implements FactoryBean<SqlSessionFactory>, InitializingBean, ApplicationListener<ApplicationEvent> {
    
    @Override
    public void onApplicationEvent(ApplicationEvent event){
        if (failFast && event instanceof ContextRefreshedEvent) {
        // fail-fast -> check all statements are completed
        this.sqlSessionFactory.getConfiguration().getMappedStatementNames();
        }
    }
    
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns="http://www.springframework.org/schema/beans"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="
       http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context 
       http://www.springframework.org/schema/beans/spring-context.xsd
       ">

    <context:component-scan base-package="com.sanyou.spring.extension"/>

</beans>

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!-- xmlns 和 targetNamespace 需要定义，结尾为sanyou，前面都一样的-->
<xsd:schema xmlns="http://sanyou.com/schema/sanyou"
            xmlns:xsd="http://www.w3.org/2001/XMLSchema"
            targetNamespace="http://sanyou.com/schema/sanyou">

    <xsd:import namespace="http://www.w3.org/XML/1998/namespace"/>

    <xsd:complexType name="Bean">
        <xsd:attribute name="class" type="xsd:string" use="required"/>
    </xsd:complexType>

    <!--  sanyou 便签的子标签，类型是Bean ，就会找到上面的complexType=Bean类型，然后处理属性  -->
    <xsd:element name="mybean" type="Bean"/>
</xsd:schema>

public class SanYouNameSpaceHandler extends NamespaceHandlerSupport {

    @Override
    public void init(){
        //注册解析 mybean 标签的解析器
        registerBeanDefinitionParser("mybean", new SanYouBeanDefinitionParser());
    }

    private static class SanYouBeanDefinitionParser extends AbstractSingleBeanDefinitionParser {
        @Override
        protected boolean shouldGenerateId(){
            return true;
        }

        @Override
        protected String getBeanClassName(Element element){
            return element.getAttribute("class");
        }

    }
}

http\://sanyou.com/schema/sanyou=com.sanyou.spring.extension.namespace.SanYouNameSpaceHandler

http\://sanyou.com/schema/sanyou.xsd=META-INF/sanyou.xsd

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns="http://www.springframework.org/schema/beans"
       xmlns:sanyou="http://sanyou.com/schema/sanyou"
       xsi:schemaLocation="
       http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://sanyou.com/schema/sanyou
       http://sanyou.com/schema/sanyou.xsd
       ">

    <!--使用 sanyou 标签，配置一个 User Bean-->
    <sanyou:mybean class="com.sanyou.spring.extension.User"/>

</beans>

public class Application {

    public static void main(String[] args){

        ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
        applicationContext.refresh();

        User user = applicationContext.getBean(User.class);

        System.out.println(user);
    }

}

com.sanyou.spring.extension.User@27fe3806

<dubbo:registry address="zookeeper://192.168.10.119:2181" />