一、aspect的定义
运行完HelloWorld以后，我们来看下aspect的基础语法：
１、定义一个切面： 关键字aspect。 这定义Java类的语法类似。
２、定义pointcut： ［修饰符(public,protected.....)］ pointcut poincut名字() : 表达式;
3、定义advice： 通知类型() ： pointcut名字(){ .......逻辑}
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一个最基本的aspect，就是这样组成的。值得一提的是：aspectj支持很多类型的pointcut，最基本的就是method call pointcut（方法级别），而Spring的aop 仅支持method call pointcut。所以，在后面陆续的使用中，你将会发现aspectj的强大， 简直强大到有点过分。而至于advice，aspectj也一样，就是５种类型。
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二、pointcut的主要类型
| Methods and Constructors | |
| call(Signature) | every call to any method or constructor matching Signature at the call site（方法和构造函数的调用点） |
| execution(Signature) | every execution of any method or constructor matching Signature （方法和构造函数的执行点） |
| Fields | |
| get(Signature) | every reference to any field matching Signature （属性的读操作） |
| set(Signature) | every assignment to any field matching Signature. The assigned value can be exposed with anargs pointcut （属性的写操作） |
| Exception Handlers | |
| handler(TypePattern) | every exception handler for any Throwable type in TypePattern. The exception value can be exposed with anargs pointcut（异常处理执行） |
| Advice | |
| adviceexecution() | every execution of any piece of advice（Advice执行） |
| Initialization | |
| staticinitialization(TypePattern) | every execution of a static initializer for any type in TypePattern (类初始化) |
| initialization(Signature) | every initialization of an object when the first constructor called in the type matchesSignature, encompassing the return from the super constructor call to the return of the first-called constructor (对象初始化) |
| preinitialization(Signature) | every pre-initialization of an object when the first constructor called in the type matchesSignature, encompassing the entry of the first-called constructor to the call to the super constructor (对象预先初始化) |
| Lexical | |
| within(TypePattern) | every join point from code defined in a type in TypePattern (捕获在指定类或者方面中的程序体中的所有连接点，包括内部类) |
| withincode(Signature) | every join point from code defined in a method or constructor matching Signature (用于捕获在构造器或者方法中的所有连接点，包括在其中的本地类) |
| Instanceof checks and context exposure | |
| this(Type or Id) | every join point when the currently executing object is an instance of Type orId's type(所有Type or id 的实例的执行点，匹配所有的连接点，如方法调用，属性设置，当前的执行对象为Account，或者其子类。) |
| target(Type or Id) | every join point when the target executing object is an instance of Type orId's type (配所有的连接点，目标对象为Type或Id) |
| args(Type or Id, ...) | every join point when the arguments are instances of Types or the types of theIds (参数类型为Type) |
| Control Flow | |
| cflow(Pointcut) | every join point in the control flow of each join point P picked out byPointcut, including P itself (捕获所有的连接点在指定的方法执行中，包括执行方法本身) |
| cflowbelow(Pointcut) | every join point below the control flow of each join point P picked out byPointcut; does not include P itself （捕获所有的连接点在指定的方法执行中，除了执行方法本身） |
| Conditional | |
| if(Expression) | every join point when the boolean Expression is true |
| Combination （逻辑／结合操作） | |
| ! Pointcut | every join point not picked out by Pointcut |
| Pointcut0 && Pointcut1 | each join point picked out by both Pointcut0 and Pointcut1 |
| Pointcut0 || Pointcut1 | each join point picked out by either Pointcut0 or Pointcut1 |
| ( Pointcut ) | each join point picked out by Pointcut |
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前面说过pointcut基于正则的语法，那么肯定也支持通配符，含义如下：
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* 表示任何数量的字符，除了(.)
.. 表示任何数量的字符包括任何数量的(.)
+ 描述指定类型的任何子类或者子接口
同java一样，提供了一元和二元的条件表达操作符。
一元操作符：!
二元操作符：||和&&
优先权同java