第三章 AOP 通过Java API创建增强

3.3.1增强类型

前置增强：org.springframework.aop.MethodBeforeAdvice

后置增强：org.springframework.aop.AfterReturningAdvice

环绕增强：org.aopalliance.intercept.MethodInterceptor

异常抛出增强：org.springframework.aop.ThrowsAdvice

引介增强：org.springframework.aop.support.DelegatingIntroductionInterceptor

3.3.2前置增强

就是在连接点方法执行之前执行的内容。

如：我们在UserDaoImpl的save()方法执行之前执行一些内容。

a、UserDao与UserDaoImpl:

publicinterfaceUserDao{
publicvoidsave();
}

publicclassUserDaoImplimplementsUserDao{
publicvoidsave(){
System.out.println("保存用户...");
}
}

b、创建一个增强类实现MethodBeforeAdvice接口

public class UserDaoBeforeAdvice implements MethodBeforeAdvice {
	public void before(Method method, Object[] args, Object object)
			throws Throwable {
		System.out.println("我是前置增强");
	}
}

c、配置

<!-- 把增强类交由spring管理 -->
	<bean id="userDaoBeforeAdvice" class="cn.framelife.spring.advice.UserDaoBeforeAdvice"></bean>

	<!-- 把目标类交由spring管理 -->
	<bean id="userDao" class="cn.framelife.spring.dao.impl.UserDaoImpl"></bean>

	<!-- 
		设置代理类 
		p:target-ref 目标对象
		p:proxyInterfaces 代理所要实现的接口，也就是目标对象的接口
		p:interceptorNames 织入的增强Bean，可以是多个，用","号分开
	-->
	<bean id="adviceUserDao" 
		class="org.springframework.aop.framework.ProxyFactoryBean"
		p:proxyInterfaces="cn.framelife.spring.dao.UserDao"
		p:interceptorNames="userDaoBeforeAdvice"
		p:target-ref="userDao"
	 />

d、main方法中测试

ApplicationContext context = new ClassPathXmlApplicationContext(new String[]{"applicationContext.xml"});
		//通过代理来获取userDao对象
		UserDao userDao = (UserDao) context.getBean("adviceUserDao");
		userDao.save();

f、结果

我是前置增强
保存用户...

3.3.3后置增强

就是在连接点方法执行之后执行的内容。

a、UserDao与UserDaoImpl:

publicinterfaceUserDao{
publicvoidsave();
}

publicclassUserDaoImplimplementsUserDao{
publicvoidsave(){
System.out.println("保存用户...");
}
}

b、创建一个增强类实现AfterReturningAdvice接口

public class UserDaoAfterAdvice implements AfterReturningAdvice {
	@Override
	public void afterReturning(Object object, Method method, Object[] args,
			Object arg3) throws Throwable {
		System.out.println("我是后置增强");
	}
}

c、配置

<bean id="userDaoBeforeAdvice" class="cn.framelife.spring.advice.UserDaoBeforeAdvice"></bean>
	<bean id="userDaoAfterAdvice" class="cn.framelife.spring.advice.UserDaoAfterAdvice"></bean>

	<bean id="userDao" class="cn.framelife.spring.dao.impl.UserDaoImpl"></bean>

	
	<bean id="adviceUserDao" 
		class="org.springframework.aop.framework.ProxyFactoryBean"
		p:proxyInterfaces="cn.framelife.spring.dao.UserDao"
		p:interceptorNames="userDaoBeforeAdvice,userDaoAfterAdvice"
		p:target-ref="userDao"
	 />

d、main方法中测试

ApplicationContext context = new ClassPathXmlApplicationContext(new String[]{"applicationContext.xml"});
		//通过代理来获取userDao对象
		UserDao userDao = (UserDao) context.getBean("adviceUserDao");
		userDao.save();

f、结果

保存用户...
我是后置增强

3.3.4环绕增强

环绕增强与struts2的AOP类似。

a、UserDao与UserDaoImpl:

publicinterfaceUserDao{
publicvoidsave();
}

publicclassUserDaoImplimplementsUserDao{
publicvoidsave(){
System.out.println("保存用户...");
}
}

b、创建一个增强类实现MethodInterceptor接口

public class UserDaoSurroundAdvice implements MethodInterceptor {

	@Override
	public Object invoke(MethodInvocation invocation) throws Throwable {
		System.out.println("环绕增强在方法前执行...");
		Object object = invocation.proceed();
		System.out.println("环绕增强在方法后执行...");
		return object;
	}

}

c、配置

<bean id="userDaoSurroundAdvice" class="cn.framelife.spring.advice.UserDaoSurroundAdvice"></bean>
	
	<bean id="userDao" class="cn.framelife.spring.dao.impl.UserDaoImpl"></bean>

	<bean id="adviceUserDao" 
		class="org.springframework.aop.framework.ProxyFactoryBean"
		p:proxyInterfaces="cn.framelife.spring.dao.UserDao"
		p:interceptorNames=" userDaoSurroundAdvice"
		p:target-ref="userDao"
	 />

d、main方法中测试

ApplicationContext context = new ClassPathXmlApplicationContext(new String[]{"applicationContext.xml"});
		//通过代理来获取userDao对象
		UserDao userDao = (UserDao) context.getBean("adviceUserDao");
		userDao.save();

f、结果

环绕增强在方法前执行...
保存用户...
环绕增强在方法后执行...

3.3.5异常抛出增强

就是在方法出现异常之后执行的代码。

a、UserDao与UserDaoImpl:

publicinterfaceUserDao{
publicvoidsave();
}

publicclassUserDaoImplimplementsUserDao{
 publicvoidsave(){
 System.out.println("保存用户...");
 //使方法在运行的时候抛出一个异常
  throw new RuntimeException("运行时异常...");

}
}

b、创建一个增强类实现ThrowsAdvice接口

public class UserDaoThrowsAdvice implements ThrowsAdvice {
	public void afterThrowing(Method method,Object[] args,Object taglet,Exception ex)throws Throwable{
		System.out.println("我是异常抛出接口");
		System.out.println(method.getName());
		System.out.println(ex.getMessage());
	}
}

c、配置

<bean id="userDaoThrowAdvice" class="cn.framelife.spring.advice.UserDaoThrowsAdvice"></bean>

<!--
	 p:proxyTargetClass="false"
	如果目标对象是一个类，而不是一个接口，我们设置为true
-->
	<bean id="userDao" class="cn.framelife.spring.dao.impl.UserDaoImpl"></bean>

	<bean id="adviceUserDao" 
		class="org.springframework.aop.framework.ProxyFactoryBean"
		p:proxyInterfaces="cn.framelife.spring.dao.UserDao"
		p:interceptorNames="userDaoThrowAdvice"
		p:target-ref="userDao"
		p:proxyTargetClass="false"
	 />

d、main方法中测试

ApplicationContext context = new ClassPathXmlApplicationContext(new String[]{"applicationContext.xml"});
		//通过代理来获取userDao对象
		UserDao userDao = (UserDao) context.getBean("adviceUserDao");
		userDao.save();

f、结果

保存用户...
Exception in thread "main" java.lang.RuntimeException: 运行时异常...
	at cn.framelife.spring.dao.impl.UserDaoImpl.save(UserDaoImpl.java:12)
	at cn.framelife.spring.dao.impl.UserDaoImpl$$FastClassByCGLIB$$18bd6dee.invoke(<generated>)
	at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:191)
	at org.springframework.aop.framework.Cglib2AopProxy$CglibMethodInvocation.invokeJoinpoint(Cglib2AopProxy.java:688)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
	at org.springframework.aop.framework.adapter.ThrowsAdviceInterceptor.invoke(ThrowsAdviceInterceptor.java:124)我是异常抛出接口
save
运行时异常...

	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
	at org.springframework.aop.framework.Cglib2AopProxy$DynamicAdvisedInterceptor.intercept(Cglib2AopProxy.java:621)
	at cn.framelife.spring.dao.impl.UserDaoImpl$$EnhancerByCGLIB$$5bbe38b0.save(<generated>)
	at cn.framelife.spring.test.Test.main(Test.java:17)

3.3.6引介增强

引介增强是为目标类创建新的方法和属性，引介增强的连接点是类级别的，不是方法级别的。通过引介增强，我们可以为目标类添加一个接口的实现，即原来目标类未实现某个接口，通过引介增强可以为目标类创建实现某个接口的代理。

a、UserDao与UserDaoImpl:

publicinterfaceUserDao{
publicvoidsave();
}

publicclassUserDaoImplimplementsUserDao{
publicvoidsave(){
System.out.println("保存用户...");
}
}

b、新建一个接口AInterface

public interface AInterface {
	public void say();
}

c、增强类继承DelegatingIntroductionInterceptor实现AInterface

public class IntroductionAdvice extends DelegatingIntroductionInterceptor implements AInterface {
	/*
	 * 实现AInterface中的方法
	 */
	public void say() {
		System.out.println("UserDao要说话");
	}

	/*
	 * 重写DelegatingIntroductionInterceptor的invoke方法
	 */
	public Object invoke(MethodInvocation mi) throws Throwable {
		System.out.println("方法执行前执行");
		System.out.println(mi.getClass().getName());
		System.out.println(mi.getMethod().getName());
		Object object = super.invoke(mi);
		System.out.println("方法执行后执行");
		return object;
	}	
}

d、配置

<bean id="userDao" class="cn.framelife.spring.dao.impl.UserDaoImpl"></bean>

	<bean id="introductionAdvice" class="cn.framelife.spring.advice.IntroductionAdvice"></bean>
	<!-- 
		代理类设置
		p:proxyTargetClass="true" 引介增强一定要通过创建子类来生成代理，所以要设置为true。
			也不需要配置p:proxyInterfaces目标类的接口
		p:interfaces 引介增强所实现的接口
	 -->
	<bean id="aProxy" 
		class="org.springframework.aop.framework.ProxyFactoryBean"
		p:interfaces="cn.framelife.spring.dao.AInterface" 
		p:interceptorNames="introductionAdvice"
		p:target-ref="userDao" 
		p:proxyTargetClass="true" />

e、main方法中测试

ApplicationContext context = new ClassPathXmlApplicationContext(new String[]{"applicationContext.xml"});
		UserDao userDao = (UserDao) context.getBean("aProxy");
		userDao.save();
		
		System.out.println("-------------");
		
		AInterface a = (AInterface)userDao;
		a.say();
		
		System.out.println("-------------");
		userDao.save();

f、结果

方法执行前执行
org.springframework.aop.framework.Cglib2AopProxy$CglibMethodInvocation
save
保存用户...
方法执行后执行
-------------
方法执行前执行
org.springframework.aop.framework.Cglib2AopProxy$CglibMethodInvocation
say
UserDao要说话
方法执行后执行
-------------
方法执行前执行
org.springframework.aop.framework.Cglib2AopProxy$CglibMethodInvocation
save
保存用户...
方法执行后执行