1.策略模式

The Strategy Pattern defines a family of algorithms,encapsulates each one,and makes them interchangeable. Strategy lets the algorithm vary independently from clients that use it

　　　　　　　　　　策略模式UML圖

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2.策略模式組成

—抽象策略角色： 策略類，通常由一個接口或者抽象類實現(xiàn)。 —具體策略角色：包裝了相關(guān)的算法和行為。 —環(huán)境角色：持有一個策略類的引用，最終給客戶端調(diào)用。 3.spring AOP策略模式使用 分析角色 —抽象策略角色--AopProxy —具體策略角色--Cglib2AopProx和JdkDynamicAopProxy —環(huán)境角色--ProxyCreatorSupport 調(diào)用方式：ProxyFactoryBean.java 1 /** 2 * Return the singleton instance of this class's proxy object, 3 * lazily creating it if it hasn't been created already. 4 * @return the shared singleton proxy 5 */ 6 private synchronized Object getSingletonInstance() { 7 if (this.singletonInstance == null) { 8 this.targetSource = freshTargetSource(); 9 if (this.autodetectInterfaces && getProxiedInterfaces().length == 0 && !isProxyTargetClass()) { 10 // Rely on AOP infrastructure to tell us what interfaces to proxy. 11 Class targetClass = getTargetClass(); 12 if (targetClass == null) { 13 throw new FactoryBeanNotInitializedException("Cannot determine target class for proxy"); 14 } 15 setInterfaces(ClassUtils.getAllInterfacesForClass(targetClass, this.proxyClassLoader)); 16 } 17 // Initialize the shared singleton instance. 18 super.setFrozen(this.freezeProxy); 19 this.singletonInstance = getProxy(createAopProxy()); 20 } 21 return this.singletonInstance; 22 }

真實代碼實現(xiàn)在DefaultAopProxyFactory.java

1 public AopProxy createAopProxy(AdvisedSupport config) throws AopConfigException { 2 if (config.isOptimize() || config.isProxyTargetClass() || hasNoUserSuppliedProxyInterfaces(config)) { 3 Class targetClass = config.getTargetClass(); 4 if (targetClass == null) { 5 throw new AopConfigException("TargetSource cannot determine target class: " + 6 "Either an interface or a target is required for proxy creation."); 7 } 8 if (targetClass.isInterface()) { 9 return new JdkDynamicAopProxy(config); 10 } 11 if (!cglibAvailable) { 12 throw new AopConfigException( 13 "Cannot proxy target class because CGLIB2 is not available. " + 14 "Add CGLIB to the class path or specify proxy interfaces."); 15 } 16 return CglibProxyFactory.createCglibProxy(config); 17 } 18 else { 19 return new JdkDynamicAopProxy(config); 20 } 21 }

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轉(zhuǎn)載于:https://www.cnblogs.com/davidwang456/archive/2013/03/21/2973853.html

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