Bean的加载方式

bean的xml方式声明

<?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"><!--    xml方式声明自己开发的bean--><bean id="cat" class="com.itheima.bean.Cat"/><bean class="com.itheima.bean.Dog"/>
<!--    xml声明第三方开发的Bean--><bean  id="dataSource" class="com.alibaba.druid.pool.DruidDataSource"/><bean  class="com.alibaba.druid.pool.DruidDataSource"/><bean  class="com.alibaba.druid.pool.DruidDataSource"/>
</beans>

bean的加载方式二：XML+注解当时声明bean

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:context="http://www.springframework.org/schema/context"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context.xsd"><!--    指定加载Bean的位置，Component--><context:component-scan base-package="com.itheima.bean,com.itheima.config"/></beans>

//@Component
@Configuration
public class DbConfig {@Beanpublic DruidDataSource dataSource(){DruidDataSource ds = new DruidDataSource();return ds;}
}

bean的加载方式三：注解方式声明配置类

@ComponentScan({"com.itheima.bean","com.itheima.config"})
public class SpringConfig3 {
}

要使用AnnotationConfigApplicationContext加载bean了

public class App3 {public static void main(String[] args) {ApplicationContext ctx = new AnnotationConfigApplicationContext(SpringConfig3.class);String[] names = ctx.getBeanDefinitionNames();for (String name : names) {System.out.println(name);}}
}

bean加载方式扩展——FactoryBean

public class DogFactoryBean implements FactoryBean<Dog> {@Overridepublic Dog getObject() throws Exception {return new Dog();}@Overridepublic Class<?> getObjectType() {return Dog.class;}@Overridepublic boolean isSingleton() {return FactoryBean.super.isSingleton();}
}