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BeanFactory 和 ApplicationContext

2016-03-18 20:06 483 查看
Spring通过一个配置文件描述Bean及Bean直接的依赖关系,利用Java语言的反射功能实例化Bean并建立Bean之间的依赖关系。Sprig的IoC容器在完成这些底层工作的基础上,还提供了Bean实例缓存、生命周期管理、Bean实例代理、事件发布、资源装载等高级服务。

Bean工厂(com.springframework.beans.factory.BeanFactory)是Spring框架最核心的接口,它提供了高级IoC的配置机制。BeanFactory使管理不同类型的Java对象成为可能,应用上下文(com.springframework.context.ApplicationContext)建立在BeanFactory基础之上,提供了更多面向应用的功能,它提供了国际化支持和框架事件体系,更易于创建实际应用。我们一般称BeanFactory为IoC容器,而称 ApplicationContext为应用上下文。但有时为了行文方便,我们也将ApplicationContext称为Spring容器。
BeanFactory是Spring框架的基础设施,面向Spring本身;ApplicationContext面向使用Spring框架的开发者,几乎所有的应用场合都直接使用ApplicationContext而非底层的BeanFactory。

1、初始化BeanFactory
beans.xml

<?xml version="1.0" encoding="UTF-8" ?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:p="http://www.springframework.org/schema/p"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd"> <bean id="car" class="com.reflect.Car"
p:brand="迈锐宝"
p:color="黑色"
p:maxSpeed="300"/>
</beans>


BeanFactoryTest:

package com.beanfactory;
import com.reflect.Car;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.core.io.Resource;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.core.io.support.ResourcePatternResolver;
import java.io.IOException;
/**
* Created by gao on 16-3-18.
*/
public class BeanFactoryTest {
public static void main(String[] args) throws IOException {
ResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
Resource res = resolver.getResource("classpath:beans.xml");
BeanFactory bf = new XmlBeanFactory(res);
System.out.println("init BeanFactory.");
Car car = bf.getBean("car", Car.class);
System.out.println("car bean is ready for use!");
}
}


在初始化BeanFactory时,必须为其提供一种日志框架,我们使用Log4J,即在类路径下提供Log4J配置文件,这样启动Spring容器才不会报错。
log4j.properties

log4j.rootLogger=INFO,A1
log4j.appender.A1=org.apache.log4j.ConsoleAppender
log4j.appender.A1.layout=org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=%d %5p [%t] (%F:%L) - %m%n


测试输出:

2016-03-18 17:19:27,045 INFO [main] (XmlBeanDefinitionReader.java:315) - Loading XML bean definitions from class path resource [beans.xml]
init BeanFactory.
car bean is ready for use!

2、ApplicationContext
ApplicationContext使用ClassPathXmlApplicationContext和FileSystemXMLApplicationContext,前者默认从类路径下加载配置文件,后者默认从文件系统中装载配置文件。在获取ApplicationContext实例后,就可以像BeanFactory一样调用getBean(beanName)返回Bean了。BeanFactory在初始化容器时,并未实例化Bean,直到第一次访问某个Bean时才实例目标Bean;而ApplicationContext则在初始化应用上下文时就实例化所以单实例的Bean。
[b]Beans:[/b]

package com.context;
import com.reflect.Car;
import org.springframework.beans.factory.annotation.Configurable;
import org.springframework.context.annotation.Bean;
/**
* Created by gao on 16-3-18.
*/
@Configurable
public class Beans {
@Bean(name = "car")
public Car buildCar() {
Car car = new Car();
car.setBrand("英菲迪尼");
car.setMaxSpeed(300);
return car;
}
}


AnnotationApplicationContext:

package com.context;
import com.reflect.Car;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
/**
* Created by gao on 16-3-18.
*/
public class AnnotationApplicationContext {
public static void main(String[] args) {
ApplicationContext ctx = new AnnotationConfigApplicationContext(Beans.class);
Car car = ctx.getBean("car", Car.class);
System.out.println(car.getBrand());
System.out.println(car.getMaxSpeed());
}
}


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