初学spring 关于IOC与AOP 使用的设计模式
Rod Johnson提出
interface21
改名为spring
IOC(Inverse of Control) 控制反转
以前程序中需要使用对象时,需要自己new一个,造成程序与对象的强耦合。
IOC 对象的生成交给spring容器完成
DI(Dependency Injection),依赖注入
IOC与DI一个意思,等价
AOP(Aspect-oriented Programming)面向切面编程
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Spring IOC使用了工厂模式
抽象产品:
Product.java
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- <span style="font-size:18px;">package com.test.simplefactory;
- public abstract class Product
- {
- }
- </span>
具体产品:
ConcreteProductA.java
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- <span style="font-size:18px;">package com.test.simplefactory;
- public class ConcreteProductA extends Product
- {
- }
- </span>
ConcreteProductB.java
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- <span style="font-size:18px;">package com.test.simplefactory;
- public class ConcreteProductB extends Product
- {
- }
- </span>
工厂类
Creator.java
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- <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>
具体应用
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
静态代理
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; // 以真实角色作为代理角色的属性
- public ProxySubject()
- {
- }
- public void request() // 该方法封装了真实对象的request方法
- {
- preRequest();
- if (realSubject == null)
- {
- realSubject = new RealSubject();
- }
- realSubject.request(); // 此处执行真实对象的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>
真实角色 房东
RealSubject.java
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- <span style="font-size:18px;">package com.test.proxy;
- //真实角色:实现了Subject的request()方法
- public class RealSubject extends Subject
- {
- public RealSubject()
- {
- }
- public void request()
- {
- System.out.println("From real subject.");
- }
- }
- </span>
客户端调用 租客
Client.java
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- <span style="font-size:18px;">package com.test.proxy;
- //客户端调用
- public class Client
- {
- public static void main(String[] args)
- {
- Subject sub = new ProxySubject();
- sub.request();
- }
- }
- </span>
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动态代理:真实对象很多,不知道代理那个真实对象,动态代理代理的是接口
抽象角色
Subject.java
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- <span style="font-size:18px;">package com.test.dynamicproxy;
- //抽象角色(之前是抽象类,此处应改为接口):
- 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;
- //代理处理器
- /**
- * 该代理类的内部属性为Object类,实际使用时通过该类的构造函数DynamicSubject(Object obj)对其赋值;
- * 此外,在该类还实现了invoke方法,该方法中的 method.invoke(sub,args);
- * 其实就是调用被代理对象的将要被执行的方法,方法参数sub是实际的被代理对象, args为执行被代理对象相应操作所需的参数。
- * 通过动态代理类,我们可以在调用之前或之后执行一些相关操作
- */
- 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>
真实角色 房东
RealSubject.java
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- <span style="font-size:18px;">package com.test.dynamicproxy;
- //具体角色
- public class RealSubject implements Subject
- {
- public RealSubject()
- {
- }
- public void request()
- {
- System.out.println("From real subject.");
- }
- }
- </span>
客户端调用 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;
- //客户端
- public class Client
- {
- public static void main(String[] args) throws Throwable
- {
- RealSubject rs = new RealSubject(); // 在这里指定被代理类
- 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核心本质: