初學spring 關於IOC與AOP 使用的設計模式
Rod Johnson提出
interface21
改名為spring
IOC(Inverse of Control) 控制反轉
以前程式中需要使用物件時,需要自己new一個,造成程式與物件的強耦合。
IOC 物件的生成交給spring容器完成
DI(Dependency Injection),依賴注入
IOC與DI一個意思,等價
AOP(Aspect-oriented Programming)面向切面程式設計
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Spring IOC使用了工廠模式
抽象產品:
Product.java
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- <span style="font-size:18px;">package com.test.simplefactory;
- public abstract class Product
- {
- }
- </span>
具體產品:
ConcreteProductA.java
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- <span style="font-size:18px;">package com.test.simplefactory;
- public class ConcreteProductA extends Product
- {
- }
- </span>
ConcreteProductB.java
[java] view plain copy
- <span style="font-size:18px;">package com.test.simplefactory;
- public class ConcreteProductB extends Product
- {
- }
- </span>
工廠類
Creator.java
[java] view plain copy
- <span style="font-size:18px;">package com.test.simplefactory;
- public class Creator
- {
- public static Product createProduct(String str)
- {
- if("A".equals(str))
- {
- return new ConcreteProductA();
- }
- else if("B".equals(str))
- {
- return new ConcreteProductB();
- }
- else
- {
- return null;
- }
- }
- }
- </span>
具體應用
Client.java
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- <span style="font-size:18px;">package com.test.simplefactory;
- public class Client
- {
- public static void main(String[] args)
- {
- Product productA = Creator.createProduct("A");
- System.out.println(productA.getClass().getName());
- Product productB = Creator.createProduct("B");
- System.out.println(productB.getClass().getName());
- }
- }
- </span>
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Spring AOP使用了代理模式
靜態代理
抽象角色
Subject.java
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- <span style="font-size:18px;">package com.test.proxy;
- // 抽象角色
- public abstract class Subject
- {
- abstract public void request();
- }
- </span>
代理角色 中介
ProxySubject.java
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- <span style="font-size:18px;">package com.test.proxy;
- //代理角色
- public class ProxySubject extends Subject
- {
- private RealSubject realSubject; // 以真實角色作為代理角色的屬性
- public ProxySubject()
- {
- }
- public void request() // 該方法封裝了真實物件的request方法
- {
- preRequest();
- if (realSubject == null)
- {
- realSubject = new RealSubject();
- }
- realSubject.request(); // 此處執行真實物件的request方法
- postRequest();
- }
- private void preRequest()
- {
- // something you want to do before requesting
- }
- private void postRequest()
- {
- // something you want to do after requesting
- }
- }
- </span>
真實角色 房東
RealSubject.java
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- <span style="font-size:18px;">package com.test.proxy;
- //真實角色:實現了Subject的request()方法
- public class RealSubject extends Subject
- {
- public RealSubject()
- {
- }
- public void request()
- {
- System.out.println("From real subject.");
- }
- }
- </span>
客戶端呼叫 租客
Client.java
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- <span style="font-size:18px;">package com.test.proxy;
- //客戶端呼叫
- public class Client
- {
- public static void main(String[] args)
- {
- Subject sub = new ProxySubject();
- sub.request();
- }
- }
- </span>
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動態代理:真實物件很多,不知道代理那個真實物件,動態代理代理的是介面
抽象角色
Subject.java
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- <span style="font-size:18px;">package com.test.dynamicproxy;
- //抽象角色(之前是抽象類,此處應改為介面):
- public interface Subject
- {
- public void request();
- }
- </span>
代理角色 中介
DynamicSubject.java
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- <span style="font-size:18px;">package com.test.dynamicproxy;
- import java.lang.reflect.InvocationHandler;
- import java.lang.reflect.Method;
- //代理處理器
- /**
- * 該代理類的內部屬性為Object類,實際使用時通過該類的建構函式DynamicSubject(Object obj)對其賦值;
- * 此外,在該類還實現了invoke方法,該方法中的 method.invoke(sub,args);
- * 其實就是呼叫被代理物件的將要被執行的方法,方法引數sub是實際的被代理物件, args為執行被代理物件相應操作所需的引數。
- * 通過動態代理類,我們可以在呼叫之前或之後執行一些相關操作
- */
- public class DynamicSubject implements InvocationHandler
- {
- private Object sub;
- public DynamicSubject()
- {
- }
- public DynamicSubject(Object obj)
- {
- sub = obj;
- }
- public Object invoke(Object proxy, Method method, Object[] args)
- throws Throwable
- {
- System.out.println("before calling " + method);
- method.invoke(sub, args);
- System.out.println("after calling " + method);
- return null;
- }
- }
- </span>
真實角色 房東
RealSubject.java
[java] view plain copy
- <span style="font-size:18px;">package com.test.dynamicproxy;
- //具體角色
- public class RealSubject implements Subject
- {
- public RealSubject()
- {
- }
- public void request()
- {
- System.out.println("From real subject.");
- }
- }
- </span>
客戶端呼叫 租客
Client.java
[java] view plain copy
- <span style="font-size:18px;">package com.test.dynamicproxy;
- import java.lang.reflect.InvocationHandler;
- import java.lang.reflect.Proxy;
- //客戶端
- public class Client
- {
- public static void main(String[] args) throws Throwable
- {
- RealSubject rs = new RealSubject(); // 在這裡指定被代理類
- InvocationHandler ds = new DynamicSubject(rs);
- Class<?> cls = rs.getClass();
- // 以下是一次性生成代理
- Subject subject = (Subject) Proxy.newProxyInstance(
- cls.getClassLoader(), cls.getInterfaces(), ds);
- subject.request();
- }
- }
- </span>
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AOP核心本質: