Spring框架中的ApplicationContext

读了外国的本书上才知道,"ApplicationContext"对象,才是构建了Spring框架的灵魂。包括全部的"依赖注入"都是在ApplicationContext内部完成的,如果说"依赖注入"是Spring框架的核心概念,那么"ApplicationContext"就是它的核心对象.

ApplicationContext对象是BeanFactory的特化,这里的特化大概意思是说:ApplicationContext对象可以看作是个功能齐全的BeanFactory。"BeanFactory"是充当Spring框架中所有Bean对象的注册表.通常BeanFactory是负责创建Bean对象,并且将各个Bean之间的依赖关系进行关联。一般的应用程序都是与ApplicationContext互交,而不是和BeanFactory互交.ApplicationContext能通过运行BeanFacotoryPostProcessors自动的处理BeanFactory.

ApplicationContext通常使用XML文件进行配置,该文件使用是简单的DTD.

如下:

<?xml version="1.0">
<!DOCTYOE beans PUBLIC"-//SPRING//DTD BEAN//EN" http://www.springframework.org/dtd/spring-beans/dtd>
<beans>
    <bean  id="cashRegister" class="org.example.CashRegisterImpl">  

         <property  name="priceMatrix" ref="priceMatrixBean"/>

    </bean>

    <bean id="priceMatrixBean" class="org.example.PriceMatrixImpl"/>

</beans>

BeanFactory对象可以有多种实例化的方式,虽然大多数情况下不用我们进行创建,但是还是可以有几种实例化的方式。

它可以InputStream作为参数实例化,也可以将org.springframework.core.io.Resource它实例化.有多种:ClassPathResource、 FileSystemResource、InputStreamResource、ServletContextResource、 UrlResource。可根据不同情况下使用.

Resource resource = new ClassPathResource("applicationContext.xml");
BeanFactory factory = new XmlBeanFactory(resource);
HelloBean hello = (HelloBean) factory.getBean("helloBean");

and

ClassPathResource res = new ClassPathResource("applicationConxtext.xml");

XmlBeanFactory factory = new XmlBeanFactory(res);

or

InputStream is = new FileInputStream("application.xml");
XmlBeanFactory factory = new XmlBeanFactory(is);
 or

ClassPathXmlApplicationContext appContext = new ClassPathXmlApplicationContext(
new String[] {"applicationContext.xml", "applicationContext-two.xml"});

BeanFactory factory = (BeanFactory) appContext; 

 

Beans element can be defined in multiple bean, if you want to take out once all of the bean can be used org.springframework.beans.factory.ListableBeanFactory

for example：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING/DTD BEAN/EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
    <bean id="helloBeanOfJustin" class="onlyfun.caterpillar.HelloBean">
        <property name="helloWord"><value>Hello!Justin!</value></property>
    </bean>
    <bean id="helloBeanOfcaterpillar" class="onlyfun.caterpillar.HelloBean">
        <property name="helloWord"><value>Hello!caterpillar!</value></property>
    </bean>
</beans>

Resource resource = new ClassPathResource("bean.xml");
        ListableBeanFactory factory = new XmlBeanFactory(resource);
       
        Map helloBeans = factory.getBeansOfType(HelloBean.class, false, false);

 If all of the "bean" is defined in an applicationContext the application is for a small can, but if the big applications, the required bean object is very large, and this time you can use: org.springframework.beans.factory. xml.XmlBeanDefinitionReader to carry out multiple bean.xml the load, it needs to org.springframework.beans.factory.support.BeanDefinitionRegistry object as a build-time parameter。

for example：

BeanDefinitionRegistry reg = new DefaultListableBeanFactory();
XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(reg);
   
// 载入bean   
reader.loadBeanDefinitions(new ClassPathResource("bean1.xml"));
reader.loadBeanDefinitions(new ClassPathResource("bean2.xml"));
....

// 获取Bean
BeanFactory bf = (BeanFactory) reg;
Object o = bf.getBean("helloBean");
....

 ApplicationContext继承了org.springframework.context.MessageResource对象。

可以使用getMessage()的各种方法来取得资源,可以实现国际化。MessageResource的一个子类,org.springframework.context.support.ResourceBundleMeaageSource,可以用它来获取资源文件。

<?xml version="1.0" encoding="UTF-8"?> 
<!DOCTYPE beans PUBLIC "-//SPRING/DTD BEAN/EN" "http://www.springframework.org/dtd/spring-beans.dtd"> 
<beans> 
    <bean id="messageSource" class="org.springframework.context.support.ResourceBundleMessageSource"> 
        <property name="basename"> //资源文件的名字
            <value>messages</value
        </property> 
    </bean> 
</beans>
>//设定了文件前缀,可以是messages_en_US.properties,messages_zh_TW.properties、messages_*.properties等等。
messages_en_US.properties内容：
userlogin=User {0} login at {1}
message_zh_TW.properties內容：
userlogin=使用者 {0} 於 {1} 登入
native2ascii message_zh_TW.properties message_zh_TW.txt
import java.util.*; 
import org.springframework.context.*; 
import org.springframework.context.support.*; 

public class Test { 
    public static void main(String[] args) throws Exception { 
        ApplicationContext context = new ClassPathXmlApplicationContext("bean.xml"); 

        Object[] arguments = new Object[] {"adminsun", Calendar.getInstance().getTime()}; 

        System.out.println(context.getMessage("userlogin", arguments, Locale.US)); 
        System.out.println(context.getMessage("userlogin", arguments, Locale.TAIWAN)); 
    } 
}
ClassPathXmlApplicationContext继承了ApplicationContext。读取xml获取bean对象。给getMessage()方法传递参数。
log4j:WARN No appenders could be found for logger (org.springframework.beans.factory.xml.XmlBeanDefinitionReader). 
log4j:WARN Please initialize the log4j system properly. 
User 良葛格 login at 10/28/04 12:52 PM 
使用者 adminsun 于 2004/10/28 下午 12:52 登入