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概述
AOP（Aspect Orient Programming），我们一般称为面向方面（切面）编程，作为面向对象的一种补充，用于处理系统中分布于各个模块的横切关注点，比如事务管理、日志、缓存等等。 SpringAOP采用的是动态代理，在运行期间对业务方法进行增强，所以不会生成新类，SpringAOP提供了对JDK动态代理的支持以及CGLib的支持。本章我们不关注aop代理类的实现，我简单实现一个指定次序的链式调用。
实现链式调用的
MethodInterceptor定义拦截器链,MethodInvocation 递归进入下一个拦截器链中。类图如下：
MethodInterceptor
public interface MethodInterceptor { Object invoke(MethodInvocation invocation) throws Throwable; }
MethodInvocation
public interface MethodInvocation { Object proceed() throws Throwable; }
AbstractAspectJAdvice
抽象类,实现MethodInterceptor
public abstract class AbstractAspectJAdvice implements MethodInterceptor{ private Method adviceMethod; private Object adviceObject; public AbstractAspectJAdvice(Method adviceMethod, Object adviceObject) { this.adviceMethod = adviceMethod; this.adviceObject = adviceObject; } public Method getAdviceMethod() { return this.adviceMethod; } public void invokeAdviceMethod() throws Throwable { adviceMethod.invoke(adviceObject); } }
AspectJBeforeAdvice
前置通知
public class AspectJBeforeAdvice extends AbstractAspectJAdvice { public AspectJBeforeAdvice(Method method, Object adviceObject) { super(method, adviceObject); } @Override public Object invoke(MethodInvocation invocation) throws Throwable{ this.invokeAdviceMethod(); Object o = invocation.proceed(); return o; } }
AspectJAfterReturningAdvice
后置通知
public class AspectJAfterReturningAdvice extends AbstractAspectJAdvice { public AspectJAfterReturningAdvice(Method method, Object adviceObject) { super(method, adviceObject); } @Override public Object invoke(MethodInvocation invocation) throws Throwable{ Object o = invocation.proceed(); this.invokeAdviceMethod(); return o; } }
ReflectiveMethodInvocation
实现MethodInvocation，proceed()方法递归实现链式调用。
public class ReflectiveMethodInvocation implements MethodInvocation { private final Object targetObject; private final Method targetMethod; private final List interceptorList; private int currentInterceptorIndex = -1; public ReflectiveMethodInvocation(Object targetObject, Method targetMethod, List interceptorList) { this.targetObject = targetObject; this.targetMethod = targetMethod; this.interceptorList = interceptorList; } @Override public Object proceed() throws Throwable { if (this.currentInterceptorIndex == this.interceptorList.size() - 1) { return invokeJoinPoint(); } this.currentInterceptorIndex++; MethodInterceptor interceptor = this.interceptorList.get(this.currentInterceptorIndex); return interceptor.invoke(this); } private Object invokeJoinPoint() throws Throwable { return this.targetMethod.invoke(this.targetObject); } }
NioCoderService
模拟service类
public class NioCoderService { public void testAop() { System.out.println("http://niocoder.com/"); } }
TransactionManager
模拟通知类
public class TransactionManager { public void start() { System.out.println("start tx"); } public void commit() { System.out.println("commit tx"); } public void rollback() { System.out.println("rollback tx"); } }
ReflectiveMethodInvocationTest
beforeAdvice->afterReturningAdvice
测试类，测试通知
public class ReflectiveMethodInvocationTest { private AspectJBeforeAdvice beforeAdvice = null; private AspectJAfterReturningAdvice afterReturningAdvice = null; private NioCoderService nioCoderService; private Tr<span style="color:transparent">来源gaodai#ma#com搞*代#码网</span>ansactionManager tx; public void setUp() throws Exception { nioCoderService = new NioCoderService(); tx = new TransactionManager(); beforeAdvice = new AspectJBeforeAdvice(TransactionManager.class.getMethod("start"), tx); afterReturningAdvice = new AspectJAfterReturningAdvice(TransactionManager.class.getMethod("commit"), tx); } public void testMethodInvocation() throws Throwable { Method method = NioCoderService.class.getMethod("testAop"); List interceptorList = new ArrayList(); interceptorList.add(beforeAdvice); interceptorList.add(afterReturningAdvice); ReflectiveMethodInvocation mi = new ReflectiveMethodInvocation(nioCoderService, method, interceptorList); mi.proceed(); } public static void main(String[] args) throws Throwable { ReflectiveMethodInvocationTest reflectiveMethodInvocationTest = new ReflectiveMethodInvocationTest(); reflectiveMethodInvocationTest.setUp(); reflectiveMethodInvocationTest.testMethodInvocation(); } }
输出:
start tx
http://niocoder.com/
commit tx
时序图 beforeAdvice->afterReturningAdvice
afterReturningAdvice->beforeAdvice
修改interceptorList的顺序
public void testMethodInvocation() throws Throwable { Method method = NioCoderService.class.getMethod("testAop"); List interceptorList = new ArrayList(); interceptorList.add(afterReturningAdvice); interceptorList.add(beforeAdvice); ReflectiveMethodInvocation mi = new ReflectiveMethodInvocation(nioCoderService, method, interceptorList); mi.proceed(); }
输出:
start tx
http://niocoder.com/
commit tx
时序图 afterReturningAdvice->beforeAdvice
代码下载
github:https://github.com/longfeizheng/data-structure-java/blob/master/src/main/java/cn/merryyou/aop
代码下载
github:https://github.com/longfeizheng/data-structure-java
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