Spring笔记二

Spring的装载和启动

Spring是通过上下文（Application Context）装载Bean的定义并组装。
XML配置的Bean用ClassPathXmlApplicationContext比较合适。该类加载位于应用程序类路径下的一个或多个xml配置文件：

    public class KnightMain    {        public static void main(String[] args) throw Exception        {            ClassPathXmlApplicationContext context=new             ClassPathXmlApplicationContext("META-INF/spring/knight.xml");            <!-如果是java配置的bean则用AnnotationConfigApplicationContext-->            Knight knight=context.getClass(Knight.class);            knight.embarkonQuest();            context.close();        }    }

应用切面

DI能够让相互协作的软件组件保持松散耦合，而面向切面变成（AOP）允许你把遍布应用各处的功能分离的功能分离出来形成可重用的组件。

例子（1）：

public class Minstrel{    private PrintStream stream;    public Minstrel(PrintStream stream){        this.stream=stream;    }    public void singBeforeQuest()    {        stream.println("探险之前调用");    }    public void singAfterQuest()    {        stream.println("探险之后调用");    }}

（2）：

    public class BraveKnigth implements Knight{        private Quest quest;        private Minstrel minstrel;        public BraveKnight(Quest quest,Minstrel minstrel){            this.quest=quest;            this.minstrel=minstrel;        }        public void embarkOnQuest() throws QuestException{            minstrel.singBeforeQuest();            quest.embark();            minstrel.singAfterQuest();        }    }

在spring中配置：

    <?xml version="1.0" encoding="UTF-8"?>    <beans xmlns="http://www.soringframeword.org/schema/beans"              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"            xmlms:aop="http://www.springframework.org/schema/aop             http://www.springframework.org/schema/aop/spring-aop-3.2.xsd             http://www.springframework.org/schema/beans             http://www.springframework.org/schema/beans/spring-beans.xsd">    <bean id="knight" class="com.springinaction.knights.BraveKnight">    <constructor-arg ref="quest" />    </bean>    <bean id="quest" class="com.springinaction.knights.SlayDragonQuest">    <constructor-arg value="#{T(System).out}" />    </bean>    <!--申明Minstrel Bean-->    <bean id="minstrel" class="com.springinction.knights.Minstrel">    <constructor-arg value="#{T(System).out}">    </bean>    <aop:config>        <aop:aspect ref="minstrel">           <!--定义切点-->            <aop:pointcut id="embark" expression="execution(* *.embarkInQuest(...))" />            <!--申明前置通知-->            <aop:before pointcut-ref="embark" method="singBeforeQuest"/>            <!--申明后置通知-->            <aop:after pointcut-ref="embark" method="singAfterQuest" />        </aop:aspect>    </aop:config>    </beans>