AOP (Aspect Oriented Programming) 是 OOP 的延續，旨在將橫切關注點（日誌、事務、安全等）與業務邏輯分離，實現解耦。本質上是動態代理機制的應用。
| 術語 | 定義 | 對應配置 |
|---|---|---|
| 切面 | 橫切關注點的模組化 | <aop:aspect> / @Aspect |
| 連接點 | 程式執行過程中的特定點（方法調用、異常拋出） | 隱含 |
| 通知 | 切面在連接點執行的動作 | <aop:before> 等 / @Before 等 |
| 切入點 | 匹配連接點的斷言表達式 | <aop:pointcut> / @Pointcut |
| 目標對象 | 被代理的業務對象 | <bean> 定義 |
| AOP 代理 | Spring 生成的代理物件（JDK 動態代理 / CGLIB） | proxy-target-class 屬性控制 |
@Before)：方法執行前，不可阻止執行@After)：方法退出時（正常/異常）@AfterReturning)：正常返回後@Around)：包圍方法執行，可控制是否執行目標方法，最強大@AfterThrowing)：拋出異常時<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="https://www.springframework.org/schema/beans"
xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
xmlns:context="https://www.springframework.org/schema/context"
xmlns:aop="https://www.springframework.org/schema/aop"
xsi:schemaLocation="
https://www.springframework.org/schema/aop https://www.springframework.org/schema/aop/spring-aop-3.1.xsd
https://www.springframework.org/schema/beans https://www.springframework.org/schema/beans/spring-beans.xsd
https://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context-3.0.xsd">
<context:component-scan base-package="cn.ysh.studio.spring.aop"/>
<aop:aspectj-autoproxy proxy-target-class="true"/> <!-- 強制 CGLIB -->
<bean id="userService" class="cn.ysh.studio.spring.aop.service.UserService"/>
</beans>
@Component
@Aspect
public class ServiceAspect {
private static final Log log = LogFactory.getLog(ServiceAspect.class);
@Pointcut("execution(* cn.ysh.studio.spring.aop.service..*(..))")
public void aspect() {} // 空方法體，供其他通知引用
@Before("aspect()")
public void before(JoinPoint jp) {
log.info("before " + jp);
}
@After("aspect()")
public void after(JoinPoint jp) {
log.info("after " + jp);
}
@Around("aspect()")
public Object around(ProceedingJoinPoint pjp) throws Throwable {
long start = System.currentTimeMillis();
try {
Object result = pjp.proceed(); // 執行目標方法
log.info("around " + pjp + " 耗時：" + (System.currentTimeMillis() - start) + "ms");
return result;
} catch (Throwable e) {
log.info("around " + pjp + " 異常：" + e.getMessage());
throw e;
}
}
@AfterReturning("aspect()")
public void afterReturn(JoinPoint jp) {
log.info("afterReturn " + jp);
}
@AfterThrowing(pointcut = "aspect()", throwing = "ex")
public void afterThrow(JoinPoint jp, Exception ex) {
log.info("afterThrow " + jp + " " + ex.getMessage());
}
}
public class Tester {
public static void main(String[] args) {
ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
UserService service = (UserService) ctx.getBean("userService");
service.get(1L);
service.save(new User());
try { service.delete(1L); } catch (Exception e) { /* 記錄日誌 */ }
}
}
before execution(User get(long)) getUser method ... around execution(User get(long)) 耗時：42ms after execution(User get(long)) afterReturn execution(User get(long)) before execution(void save(User)) saveUser method ... around execution(void save(User)) 耗時：2ms after execution(void save(User)) afterReturn execution(void save(User)) before execution(boolean delete(long)) delete method ... around execution(boolean delete(long)) 耗時：5ms with exception ... after execution(boolean delete(long)) afterReturn execution(boolean delete(long)) // 注意：異常時 afterReturn 仍執行 WARN - Delete user : Null return value from advice...
<beans ... xmlns:aop="https://www.springframework.org/schema/aop" ...>
<bean id="serviceAspect" class="cn.ysh.studio.spring.aop.aspect.ServiceAspect"/>
<aop:config>
<aop:aspect id="simpleAspect" ref="serviceAspect">
<aop:pointcut expression="execution(* cn.ysh.studio.spring.aop.service..*(..))" id="simplePointcut"/>
<aop:before pointcut-ref="simplePointcut" method="before"/>
<aop:after pointcut-ref="simplePointcut" method="after"/>
<aop:after-returning pointcut-ref="simplePointcut" method="afterReturn"/>
<aop:after-throwing pointcut-ref="simplePointcut" method="afterThrow" throwing="ex"/>
<!-- 環繞通知需方法簽名為 Object method(ProceedingJoinPoint) -->
<aop:around pointcut-ref="simplePointcut" method="around"/>
</aop:aspect>
</aop:config>
</beans>
execution(modifiers-pattern? ret-type-pattern declaring-type-pattern? name-pattern(param-pattern) throws-pattern?)
modifiers-pattern：權限修飾符（可選）ret-type-pattern：返回類型（**必填**），* 表任意declaring-type-pattern：類全路徑（可選），支援 .. 遞歸匹配子包name-pattern：方法名（**必填**），* 表任意param-pattern：參數列表，**必填**，(..) 表任意參數throws-pattern：異常（可選）| 表達式 | 含義 |
|---|---|
execution(* *(..)) | 匹配所有方法 |
execution(public * com.svc.UserService.*(..)) | 匹配 UserService 所有 public 方法 |
execution(* com.svc..*.*(..)) | 匹配 com.svc 及子包所有類的所有方法 |
&& (and)：execution(* foo()) && execution(* bar())|| (or)：within(com.pkg1) || within(com.pkg2)! (not)：!execution(* setter())within：限定類範圍this：代理物件類型target：目標物件類型args：參數類型@annotation：標註特定註解的方法<aop:config proxy-target-class="true"> 或 @EnableAspectJAutoProxy(proxyTargetClass = true)掌握 AOP 核心在於理解「切入點精準匹配」與「通知類型正確選擇」，環繞通知雖強大但需謹慎使用 ProceedingJoinPoint.proceed()，否則目標方法不會執行。
