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出门在外也不愁spring之AOP
Spring之AOP篇：
AOP框架是Spring的一个重要组成部分.但是Spring IOC
并不依赖于AOP,这就意味着你有权力选择是否使用AOP,AOP作为Spring
IOC容器的一个补充,使它成为一个强大的中间件解决方案。
一、AOP(Aspect-Oriented Programming)
AOP的目标:横切关注点& 这种问题用面向对象很难解决
& AOP是用来解决什么问题的呢？
横越多个模块的业务关注点，比如记录日志,事务管理
&1、AOP的解决方案——拦截
&& 1)由谁来拦截？－－代理类Proxy
和本类实现同一个接口
就像是这样:action发出命令－－代理类(处理一些操作)－－本类
&& 2)拦截的过程:
I.将Proxy(如UserServiceProxy)交给调用者(如UserAction),调用者调用需要的方法
II.Proxy先拦截该方法,执行拦截逻辑
III.然后执行调用者真正的实现类(如UserServiceImp)
&& 3)核心概念：
a、代理对象Proxy:是核心,负责拦截,由工具自动创建
b、拦截器(Interceptor):实现拦截逻辑的对象
c、目标对象(Target):是Proxy所代理的对象,是已有的类
& 以上三个类实现了一个“金三角”
Proxy--拦截--&Interceptor--实现拦截逻辑--处理目标对象--&Target
&2、代理如何实现？
有两种方式:
1)JDK动态代理(使用这个比较多)
&&&&&&&&&&&
由JDK自带的动态代码生成技术,可以对实现了接口的类进行处理
对没有实现任何接口的类进行处理
&这两种方式的共同点：(都是在后台自动生成的)
&&在程序运行期间,动态的生成代码并进行动态编译和加载
问题：Spring的AOP是如何实现代理的？是自己实现的吗？
注：Spring借用了JDK动态代理和CGLib来实现代理对象。
Spring进行如下判断来实现代理：
&&i、如果目标类实现了接口，Spring则调用JDK动态代理；
&&ii、反之，调用CGLib
Proxy是核心：
创建Proxy的方法：ProxyFactoryBean
&&bean id="arithProxy"
class="org.springframework.aop.framework.ProxyFactoryBean"&
&property name="target"
ref="arith"/&
name="interceptorNames"&
&!--&value&logBefore&/value&
&&&&&&&&&&
&value&logAfter&/value&
&&&&&&&&&&
&value&logThrows&/value&
&value&logAround&/value&
&/property&
JDK动态代理的实现方式:(工厂模式)
&&UserDao userDao = new
UserDaoImp();
&&UserDao proxy = (UserDao)
&&Proxy.newProxyInstance(userDao.getClass().getClassLoader(),
&&&&userDao.getClass().getInterfaces(),
LogHandler(userDao));
二、Spring中的AOP方式(在Spring中将拦截称为通知)
拦截逻辑放在Advice之中,Advice按时间将拦截器分为四类：
1)Before Advice：方法执行之前进行拦截
&&& public class
LogBeforeAdvice implements MethodBeforeAdvice{
&//Method method拦截的方法
&//Object[] args 方法中的参数
&//target 目标对象
&@Override
&public void before
&(Method method, Object[] args, Object
Throwable {
&&MyLogger logger = new
MyLogger();
&&System.out.println("Methods:"+method.getName()+
begins, args:"+Arrays.toString(args));
&&& 2)After
Advice:方法执行之后进行拦截
& public class LogAfterAdvice implements
AfterReturningAdvice{
&@Override
&public void afterReturning(Object resultValue,
Method method, Object[] args,
target) throws Throwable {
&&MyLogger logger = new
MyLogger();
&&System.out.println("Methods:"+method.getName()+
ends, result:"+resultValue);
&& 3)AfterThrowing
Advice：方法异常结束之后进行拦截
& public class LogThrowingAdvice implements
ThrowsAdvice {
&//ThrowsAdvice 没有方法,但方法名必须是afterThrowing
&public void
afterThrowing(IllegalArgumentException e)
&throws Throwable{
&&MyLogger logger = new
MyLogger();
&&logger.log("IllegalArgumentException！");
&& 4)Around Advice：环绕通知
& public class LogAroundAdvice implements
MethodInterceptor {
&//MethodInvocation相当于Method的包装
&@Override
&public Object invoke(MethodInvocation
methodInvocation)
&throws Throwable {
&&MyLogger logger = new
MyLogger();
&&&//methodInvocation.getMethod()获得方法
&&&//methodInvocation.getArguments()获得方法的参数
&&&logger.log("before:"+
&&&&&methodInvocation.getMethod().getName()+
args:"+methodInvocation.getArguments());
&&&//在环绕通知里面,必须执行目标方法!!!!!!!!!!!!!!
&&&Object result
= methodInvocation.proceed();
&&&logger.log("ends:"+
&&&&&methodInvocation.getMethod().getName());
&&} catch (Exception e) {
&&&logger.log("Exception:"+e.getMessage());
注意:虽然环绕通知包含了另外三种,但还是要依据业务逻辑来选择,这样有利于代码的编程量
并且环绕通知最好不要和另外三种混用,并且并许执行目标方法proceed().
&也可以大致分成两组——
&i、BeforeAdvice, AfterReturning, Throwing
&ii、AroundAdvice：需要在内部负责调用目标类的方法。
注意：AroundAdvice应单独使用
&!-- Target Object --&
&bean id="arith"
class="myspring.calculator.ArithmeticCalculatorImp"&&/bean&
&!-- Advice --&
&bean id="logBefore"
class="myspring.aop.LogBeforeAdvice"/&
&bean id="logAfter"
class="myspring.aop.LogAfterAdvice"/&
&bean id="logThrows"
class="myspring.aop.LogThrowingAdvice"/&
&bean id="logAround"
class="myspring.aop.LogAroundAdvice"/&
&!-- Proxy --&
&bean id="arithProxy"
class="org.springframework.aop.framework.ProxyFactoryBean"&
&property name="target"
ref="arith"/&
name="interceptorNames"&
&value&logBefore&/value&
&value&logAfter&/value&
&value&logThrows&/value&
&value&logAround&/value&
&/property&
在test类中这样用:ApplicationContext ac =
ClassPathXmlApplicationContext("aop-base.xml");
&&IArithmeticCalculator proxy
&&&(IArithmeticCalculator)ac.getBean("arithProxy");
&面试中可能会问到：
proxyTargetClass属性
&&将其加入到代理bean中去，则Spring将调用CGLib来实现创建Proxy对象。
&&&&&&&&&&&&&&&&&&
(无论Target有无实现接口)
&bean id=""
class="....ProxyFactoryBean"&
&property name="proxyTargetClass" value="true"
&三、Spring AOP基本方式& AspectJ
Spring2.5之后用的
Spring对AspectJ的支持
应用于有多个target,不想一个一个的配置时,用AspectJ&&&&&
1)POJO类(Aspect类)，使用@Aspect&
&&基本信息：Advice和Pointcut&&
2)定义Bean：在Bean定义文件中定义这个Aspect类&
3)启用Spring的自动代理
&&&aop:aspectj-autoproxy
&1、JoinPoint（连接点）：被拦截的方法
&&&&&&&&&&&&&&&
程序执行过程中的点,就好像方法中的一个调用,
&&或者一个特别的被抛出的异常
&&&&&&&&&&&&&&
在Spring AOP中,一个连接点通常是方法调用.
&&&Spring并不明显地使用"连接点"作为术语，
&&连接点信息可以通过MathodInvocation的参数穿过拦截器访问,
&&相当于实现org.springframework.aop.Pointcut接口.
&2、JoinPoint对象
&&获取连接点信息（获取目标方法以及目标对象的信息）&
&1）目标方法：
&&i、getSignature()：方法签名
&&&&joinPoint.getSignature().getName()
&&ii、getArgs()：方法的实参（方法的实际参数）
&&&&&&&&&&&&&&&&&
joinPoint.getArgs()
&&打印输出时:Arrays.toString(joinPoint.getArgs())
&2）目标对象：& getTarget()
&&&&目标对象实际类型：getTarget().getClass()
&3、PointCut（切入点）：一组连接点。
&&&&&&&&&&&&&&&
作用：定义了一组被拦截的方法&
&&PointCut(切入点):当一个通知被激活的时候,
&&会指定一些连接点.一个AOP框架必须允许开发者指定切入点。
&&一个AOP框架必须允许开发者指定切入点:例如使用正则表达式.
&&只有引入了切入点,才能很好的进行拦截
&&PointCut的意义：可以一次性定义多个类的
&&&&多个方法作为拦截目标（即JoinPoint）
&&PointCut代表了Target
一组Target组成了PointCut
&&一组Target可以理解为一个类的多个方法,或者多个类的多个方法
&&代理、拦截器、目标
&&PointCut
&&&在AspectJ中，切入点是用PointCut
Expression来
&&&定义的。（切入点表达式可以理解为过滤条件）
&&&PointCut表达式
execution(表达式)
&&&&表达式&
一个表达式就是一个匹配规则
myspring.calculator.IArithmeticCalculator.add(..)
&&*理解为public void
myspring.calculator.IArithmeticCalculator.add(int a,int b)
&&* 取代public void
通配一切字符&&&
&&&Spring自动代理（即Spring自动生成Proxy对象）
&&&&用&aop:aspectj-autoproxy
&Pointcut表达式语法
&1)方法级别& —— execution
&&execution(* *.*(..))
：所有类的方法
&&execution(public *
somepackage.SomeClass.someMethod(..))
&&总结：execution是对方法签名进行匹配
&2)对象级别（类级别）—— within
&within(somepackage.*)：somepackage包下所有的类
&within(com.dang.service.*Service)
&即 com.dang.service包下所有以Service结尾的类
&within(somepackage..*)：somepackage以及所有子包中的类
&within(somepackage.SomeInterface+)：SomeInterface接口的所有实现类
&总结：within是对类名(带包名)进行匹配。&拦截这个类的所有方法&
4、Aspect类的组成& 一般都用注解 重点
&&1）Advice（AspectJ中的通知类型）
&&&i、Before
//@Before("LogPointcuts.logAdd()") 方法1
&&&&&&&&&&&
@Before("execution(* *.*(..))") 方法2
public void logBefore(JoinPoint joinPoint){
logger.log("{before} the method: "
&&+joinPoint.getSignature().getName()+
args:"+Arrays.toString(joinPoint.getArgs()));&
&&&&&&&&&&&&
注:方法1和方法2都是可以的,方法1的话需要在定义一个方法.
&&在同一个类或不同的类都是可以的 直接调用这个方法
&&&&&&&&&&&&&&&&&
@Pointcut("execution(* *.*(..))")
public void logOperation(){}
&&&ii、AfterReturning
&&@AfterReturning(pointcut="execution(*
*.*(..))",
&&&returning="result")
&&& public void
afterReturning(JoinPoint joinPoint,Object result){
&& logger.log("{AfterReturning}
the method: "
&&+joinPoint.getSignature().getName()
result:"+result);&
&&注意:方法有两个参数,在注解中的returning的值必须和Object的值完全一样
&&&iii、AfterThrowing
&&@AfterThrowing(pointcut="execution(*
*.*(..))",
&&&throwing="e")
&&& public void
afterThrowing(JoinPoint joinPoint,IllegalArgumentException
&&logger.log("{AfterThrowing} the
&&+joinPoint.getSignature().getName()
&&+" e:"+e.getMessage());
&&&iv、After：相当于finally，它在AfterReturning
&&&&&和AfterThrowing之后执行。
&&&&&它的作用——一般为释放资源（如关闭Connection）
&&@After("execution(*
*.*(..))")
&public void after(JoinPoint joinPoint){
&&logger.log("{After}
method:"+joinPoint.getSignature().getName());
&&注意:After是肯定是要在最后执行的,
&&&v、Around
&&@Around("execution(*
*.*(..))")
&public Object logAround(ProceedingJoinPoint
joinPoint) throws Throwable{
&&logger.log("{Arount}Before
&&&&+joinPoint.getSignature().getName());
&&&&&&&&&&&&&&&&&&&&&&
//一定不要忘记调用目标方法
&&&Object result
= joinPoint.proceed();
&&&logger.log("{Arount}After
&&&&&+joinPoint.getSignature().getName()
result:"+result);
//返回目标方法的返回值
&&catch(IllegalArgumentException
&&&logger.log("{Around}Exception:Illegal
&&&&&+Arrays.toString(joinPoint.getArgs()));
&&注意:Around最好不要和其他四种同时使用
&&把处理日志的代码放到一起就是切面,模块化(Aspect)
& 5.Introduction(引入)
&& 1)Introduction的定义
&&给正在运行的程序中的对象添加方法。
&&&其实是一种动态技术
2)问题：如何给ArithmeticCalculatorImp类加入
&&&求最大值和最小值的方法
假设：最大值和最小值的方法已经存在，且分别属于不同的类。
&extends MaxCalculatorImp, MinCalculatorImp
不行,java不允许多继承
&& 3)要点：
&a、实现一个POJO类
&&定义@DeclareParents来"继承"的父类
@DeclareParents(
&&value="myspring.calculator.ArithmeticCalculatorImp",
&&defaultImpl=MaxCalculatorImp.class
&private MaxCalculator maxC
&@DeclareParents(
&&&value="myspring.calculator.ArithmeticCalculatorImp",
&&&defaultImpl=MinCalculatorImp.class
&&private MinCalculator
&b、定义这个Bean：在Bean定义文件中声明一下。
class="myspring.calculator.CalculatorIntroduction"&&/bean&
在test类中测试时:ApplicationContext ac =
ClassPathXmlApplicationContext("aop.xml");
&&IArithmeticCalculator cal =
(IArithmeticCalculator)
&&ac.getBean("arith");
&&cal.add(2, 3);
&&cal.div(4, 3);
&&MaxCalculator max =
(MaxCalculator)
&&max.max(3, 6);
&&MinCalculator min =
(MinCalculator)
&&min.min(3, 6);
已投稿到：
以上网友发言只代表其个人观点，不代表新浪网的观点或立场。POINTS GURU: Here's How Frequent Fliers Are Screwing Up Their Miles
Call them miles, call the points, call them whatever you like, but when it comes to travel, the long
is among the hottest topics on the Web.
What can be one of the simplest ways to save on travel is also one of the most confusing tricks of the trade for consumers to master.
by which travel rewards cards to invest in, we tapped one of the best experts in the game,
to walk them through the process.
"I never give people guidelines on what you should and shouldn't do because everyone's needs are different," Kelly says.
What's a bit easier is picking out exactly where some travelers are going wrong when it comes to cashing in on their points. Here's where Kelly says we're tripping up:
At the grocery store: One of the best places to ea it's at the store. "These days with miles the best way to earn them is by shopping with credit cards," Kelly says. "I would say just take out travel rewards cards for everyday spending and when you travel." Just be sure you nab a card that waives foreign transaction fees, which can be a real killer.
Forgetting the class system: The thing about upgrading tickets is that's it's not as simple as most consumers seem to think. "People just assume they can upgrade, but they don't pay attention to fare classes," Kelly says. "Most of what you find online are cheaply discounted coach prices and most airlines, like Delta, require full-fare coach (tickets) to upgrade on international flights." And even then, some upgrades can cost as much as $3,000.
Tunnel vision: Some fliers will do whatever it takes to book flights to earn more points, even if it means
on another carrier. That's not always the smartest move, especially when you consider each mile is worth about two cents. "Cash is king and yes, it's good to have a good mileage strategy, but I wouldn't pay a ton extra just to earn miles," Kelly says.
Putting all your points in one basket: Spread the love and look for cards that let you transfer your points across hotel stays, car rentals and airlines.
Letting points expire: Some frequent flier points disappear if you leave your account inactive for a certain period of time, usually after 18 months, Kelly says. "No one should let their points expire. All you need to do is buy an
song and that clock is reset." Try signing up for a miles tracking site l that will ping you with an alert when you're about to lose them.
Using miles too quickly: If you want to stretch your dollar furthest, give your miles time to really accrue before you start applying them to travel. "I buy almost all my domestic tickets and I redeem my miles for international trips in business or first class."
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