spring aop之鏈式呼叫
摘要：
關關雎鳩，在河之洲。窈窕淑女，君子好逑。
概述
AOP （ Aspect Orient Programming ），我們一般稱為面向方面（切面）程式設計，作為面向物件的一種補充，用於處理系統中分佈於各個模組的橫切關注點，比如事務管理、日誌、快取等等。 Spring AOP ...
關關雎鳩，在河之洲。窈窕淑女，君子好逑。
概述
AOP （ Aspect Orient Programming ），我們一般稱為面向方面（切面）程式設計，作為面向物件的一種補充，用於處理系統中分佈於各個模組的橫切關注點，比如事務管理、日誌、快取等等。 Spring AOP 採用的是動態代理，在執行期間對業務方法進行增強，所以不會生成新類， Spring AOP 提供了對 JDK 動態代理的支援以及CGLib的支援。本章我們不關注 aop 代理類的實現，我簡單實現一個指定次序的鏈式呼叫。
實現鏈式呼叫的
MethodInterceptor 定義攔截器鏈, MethodInvocation 遞迴進入下一個攔截器鏈中。類圖如下：
MethodInterceptor
public interface MethodInterceptor {
Object invoke(MethodInvocation invocation) throws Throwable;
}
MethodInvocation
public interface MethodInvocation {
Object proceed() throws Throwable;
}
AbstractAspectJAdvice
抽象類,實現 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
後置通知
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
實現 MethodInvocation ， proceed() 方法遞迴實現鏈式呼叫。
public class ReflectiveMethodInvocation implements MethodInvocation {
private final Object targetObject;
private final Method targetMethod;
private final List<MethodInterceptor> interceptorList;
private int currentInterceptorIndex = -1;
public ReflectiveMethodInvocation(Object targetObject, Method targetMethod, List<MethodInterceptor> 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
模擬 service 類
public class NioCoderService {
public void testAop() {
System.out.println("http://niocoder.com/");
}
}
TransactionManager
模擬通知類
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
測試類，測試通知
public class ReflectiveMethodInvocationTest {
private AspectJBeforeAdvice beforeAdvice = null;
private AspectJAfterReturningAdvice afterReturningAdvice = null;
private NioCoderService nioCoderService;
private TransactionManager 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<MethodInterceptor> 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();
}
}
輸出:
start tx http://niocoder.com/ commit tx
時序圖 beforeAdvice->afterReturningAdvice
afterReturningAdvice->beforeAdvice
修改 interceptorList 的順序
public void testMethodInvocation() throws Throwable {
Method method = NioCoderService.class.getMethod("testAop");
List<MethodInterceptor> interceptorList = new ArrayList<>();
interceptorList.add(afterReturningAdvice);
interceptorList.add(beforeAdvice);
ReflectiveMethodInvocation mi = new ReflectiveMethodInvocation(nioCoderService, method, interceptorList);
mi.proceed();
}
輸出:
start tx http://niocoder.com/ commit tx
時序圖 afterReturningAdvice->beforeAdvice
程式碼下載
- github: https://github.com/longfeizheng/data-structure-java/blob/master/src/main/java/cn/merryyou/aop