用代码学习Spring：IoC、AOP

1 从http://www.springframework.org下载Spring

2 用eclipse新建Java项目

3 建立我们的业务方法接口

public interface BusinessObject {

public void doSomething();

public void doAnotherThing();

}

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;public interface BusinessObject {

public void doSomething();

public void doAnotherThing();

}

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

4
实现业务方法，注意这是的setWords使用了依赖注入，所谓依赖注入就是把配置文件中的字符串什么的在程序运行时“自动”放到我们的程序中来。如果不
是这样，我们就只能在代码中固化这些东西，从而违背了面向对象的依赖倒置原则，还有一种满足依赖倒置的方法，即依赖查询，这就是所谓的factory模
式，即在代码中请求某种抽象的东西，然后根据配置得到它，但这种办法向对于依赖注入多了对环境的依赖，且代码冗余，EJB的JNDI查询就属于这种。另外
我们的Spring配置文件是以bean为核心的，就是我们写的一个类，在XML中描述它的名称、位置和涵盖的内容、关系。

public class BusinessObjectImpl implements BusinessObject {

private String words;

public void setWords(String words){

this.words = words;

}

public void doSomething() {

Log log = LogFactory.getLog(this.getClass());

log.info(words);

}

public void doAnotherThing() {

Log log = LogFactory.getLog(this.getClass());

log.info("Another thing");

}

}public class BusinessObjectImpl implements BusinessObject {

private String words;

public void setWords(String words){

this.words = words;

}

public void doSomething() {

Log log = LogFactory.getLog(this.getClass());

log.info(words);

}

public void doAnotherThing() {

Log log = LogFactory.getLog(this.getClass());

log.info("Another thing");

}

}

5 建立一个运行方法类，从配置文件spring-beans.xml中读入bo这个类的定义，然后实例化一个对象

import org.springframework.beans.factory.xml.XmlBeanFactory;

import org.springframework.core.io.ClassPathResource;

public class Main {

public static void main(String[] args){

XmlBeanFactory xbf = new XmlBeanFactory(new ClassPathResource("spring-beans.xml"));

BusinessObject bo = (BusinessObject)xbf.getBean("bo");

bo.doSomething();

bo.doAnotherThing();

}

}import org.springframework.beans.factory.xml.XmlBeanFactory;

import org.springframework.core.io.ClassPathResource;

public class Main {

public static void main(String[] args){

XmlBeanFactory xbf = new XmlBeanFactory(new ClassPathResource("spring-beans.xml"));

BusinessObject bo = (BusinessObject)xbf.getBean("bo");

bo.doSomething();

bo.doAnotherThing();

}

}

6 建立一个拦截器类invoke是MethodInterceptor必须实现的方法，表示拦截时的动作，大家仔细体会代码中的含义

import org.aopalliance.intercept.MethodInterceptor;

import org.aopalliance.intercept.MethodInvocation;

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

public class MyInterceptor implements MethodInterceptor {

private String before, after;

public void setAfter(String after) {

this.after = after;

}

public void setBefore(String before) {

this.before = before;

}

public Object invoke(MethodInvocation invocation) throws Throwable {

Log log = LogFactory.getLog(this.getClass());

log.info(before);

Object rval = invocation.proceed();

log.info(after);

return rval;

}

}import org.aopalliance.intercept.MethodInterceptor;

import org.aopalliance.intercept.MethodInvocation;

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

public class MyInterceptor implements MethodInterceptor {

private String before, after;

public void setAfter(String after) {

this.after = after;

}

public void setBefore(String before) {

this.before = before;

}

public Object invoke(MethodInvocation invocation) throws Throwable {

Log log = LogFactory.getLog(this.getClass());

log.info(before);

Object rval = invocation.proceed();

log.info(after);

return rval;

}

}

7
建立配置文件组织上面的类之间的关系，AOP有切入点和增强这两个重要的概念，把两个概念结合到一起，就是一个在某个方法执行的时候附加执行，切入点表示
在哪里附加，增强表示附加什么，配置文件中的myPointcut表示切入点，myInterceptor表示增强的内容，myAdvisor表示增强
器，即两者的结合，在bo这个bean中，我们把这个增强器附加到了bo这个bean上。

<?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="businessObjectImpl" class="BusinessObjectImpl">

<property name="words">

<value>正在执行业务方法</value>

</property>

</bean>

<bean id="myInterceptor" class="MyInterceptor">

<property name="before">

<value>执行业务方法前</value>

</property>

<property name="after">

<value>执行业务方法后</value>

</property>

</bean>

<bean id="myPointcut" class="org.springframework.aop.support.JdkRegexpMethodPointcut">

<property name="patterns">

<list>

<value>BusinessObject.doSomething</value>

</list>

</property>

</bean>

<bean id="myAdvisor" class="org.springframework.aop.support.DefaultPointcutAdvisor">

<property name="pointcut" ref="myPointcut"/>

<property name="advice" ref="myInterceptor"/>

</bean>

<bean id="bo" class="org.springframework.aop.framework.ProxyFactoryBean">

<property name="target">

<ref local="businessObjectImpl"/>

</property>

<property name="proxyInterfaces">

<value>BusinessObject</value>

</property>

<property name="interceptorNames">

<list>

<value>myInterceptor</value>

<value>myAdvisor</value>

</list>

</property>

</bean>

</beans><?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="businessObjectImpl" class="BusinessObjectImpl">

<property name="words">

<value>正在执行业务方法</value>

</property>

</bean>

<bean id="myInterceptor" class="MyInterceptor">

<property name="before">

<value>执行业务方法前</value>

</property>

<property name="after">

<value>执行业务方法后</value>

</property>

</bean>

<bean id="myPointcut" class="org.springframework.aop.support.JdkRegexpMethodPointcut">

<property name="patterns">

<list>

<value>BusinessObject.doSomething</value>

</list>

</property>

</bean>

<bean id="myAdvisor" class="org.springframework.aop.support.DefaultPointcutAdvisor">

<property name="pointcut" ref="myPointcut"/>

<property name="advice" ref="myInterceptor"/>

</bean>

<bean id="bo" class="org.springframework.aop.framework.ProxyFactoryBean">

<property name="target">

<ref local="businessObjectImpl"/>

</property>

<property name="proxyInterfaces">

<value>BusinessObject</value>

</property>

<property name="interceptorNames">

<list>

<value>myInterceptor</value>

<value>myAdvisor</value>

</list>

</property>

</bean>

</beans>

8 运行Main类，观察控制台输出结果，重新审查代码，反思为什么会出现这种结果。