IOC

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1 Inversion of Control (IoC) 控制反轉問題 IoC 概念 1 程式中業務邏輯至少需兩個或以上物件合作完成每個物件在使用合作物件時, 要使用 new object() 耦合度提高 IoC 解決 Spring 容器實現這些相互依賴物件的創建的生命周期關係協調工作說明找女朋友常見情況, 到處看哪裡有漂亮女孩, 打聽興趣愛好 line, 想辦法認識, 投其所好要, 必須自己設計和面對每個環節傳統程式設計, 在物件中, 若要使用其他物件, 須自己 new 一個, 或從 JNDI 中查詢, 使用完後要將物件銷毀, 物件會和其他的介面或類別耦合 2 1

2 IoC 概念 2 IoC 像透過婚姻介紹所找女朋友, 在兩物件之間引入媒介婚介管理很多男女資料需求者向婚介提出要求條件, 婚介按照要求提供, 需求者只需和她談戀愛結婚如果婚介給的人選不符合要求, 需求者就會拋出異常整個過程不由需求者控制, 而是婚介類似容器的機構控制所有類別都跟 spring 容器登記, 告訴 spring 需求者資料, 需要什麼東西,spring 在系統運行到適當時候, 把要的東西主動給需求者, 同時也把需求者交給其他物件需要的資料所有類別創建銷毀都由 spring 控制, 控制物件生存週期不再是引用它的物件, 而是 spring 對某具體物件, 以前是它控制其他物件, 現在是所有物件都被 spring 控制, 因此稱為控制反轉 3 IoC 概念 3 IoC 重點在系統運行中, 透過 DI 動態向某物件提供它所需要的其他物件例如物件 A 需操作資料庫, 之前要在 A 中撰寫程式獲得 Connection 物件 Spring 架構 : 告訴 spring,a 中需一個 Connection, 至於這個 Connection 如何建構, 何時建構,A 不需知道系統運行時,spring 會在適當時候製造一個 Connection, 像打針一樣, 注射到 A 中, 完成對各物件之間關係的控制 A 需依賴 Connection 才能運行, 這個 Connection 是由 spring 注入到 A 中 DI 的實現為利用 Java 反射機制 (reflection) 允許程式在運行時動態生成物件執行物件方法改變物件屬性, Spring 透過反射來實現注入 4 2

3 Dependency Injection 1 DI 分三種注入方式 : 建構子注入 (Constructor Injection) 屬性注入 (Setter Injection) 介面參數注入 (Interface Injection) 建構子注入 (Constructor Injection), 最常用的方式 public class ObjA{ private IObj obj; public void ObjA(IObj obj) { this.obj = obj; public void SomeAction() { obj.dowork(); 5 Dependency Injection 2 屬性注入 (Setter Injection), 適合相依物件需要和外部環境互動 public class ObjA{ private IObj obj; public IObj Obj { get { return this.obj; set { this.obj = value; public void SomeAction() { if (this.obj == null) { throw new ArgumentNullException("obj", "obj is null"); obj.dowork(); 6 3

$dowork(); 7 套用 IoC 之前 Dependence Inversion 4 public class Robot { private Car _car = null; public Robot(Car car) { _car = car; public void Work() { _car.$

4 Dependency Injection 3 介面參數注入 public class ObjA{ public void SomeAction(IObj obj) { if (obj == null) { throw new ArgumentNullException("obj", "obj is null"); obj.dowork(); 7 套用 IoC 之前 Dependence Inversion 4 public class Robot { private Car _car = null; public Robot(Car car) { _car = car; public void Work() { _car.run(); public class Car { public void Run() { 8 4

$Dependence Inversion 5 套用 IoC 之後 public class Robot { private ICar _car = null; public Robot(ICar car) { _car = car; public void Work() { _car.$

5 Dependence Inversion 5 套用 IoC 之後 public class Robot { private ICar _car = null; public Robot(ICar car) { _car = car; public void Work() { _car.run(); public interface Icar { void Run(); public class Car : Icar { public void Run() { 狹義論, 切割物件相依性時, 可套用 DI 廣義論, 架構子系統或應用程式層時, 也可套用 DI,DI 實做切割相依性重用上層, 抽換下層設計模式 9 Inversion of Control for Java 1 注入字串,HelloWorld 類別 beans-config.xml 檔 <?xml version="1.0" encoding="utf-8"?> <beans xmlns=" xmlns:xsi=" xmlns:aop=" xmlns:context=" xmlns:flow=" xmlns:jms=" xmlns:jee=" xmlns:lang=" xmlns:osgi=" xmlns:tx=" xmlns:util=" xmlns:p=" xsi:schemalocation=" "> 10 package com; public class HelloWorld { private String mymsg; private String mymsg2; public void setmsg(string m) { this.mymsg = m; public String getmsg() { return this.mymsg; public void setmsg2(string m2) { this.mymsg2 = m2; public String getmsg2() { return this.mymsg2; 5

6 Inversion of Control for Java 2 beans-config.xml 檔  <bean id="mybean" class="com.helloworld">  <property name="msg" value="hi!shadow" /> <! 若 setxxx 方法的 XXX 名稱剛好都大寫, 則要全給大寫, 後面的 value 為要注入的字串 --> <property name="msg2" value="hi!shadow Two" /> </bean> </beans> 11 寫 JSP, 把該物件值取出來 Inversion of Control for Java 3 <%@page import="org.springframework.context.support.classpathxmlapplicationcontext"%> <%@page import="org.springframework.context.applicationcontext"%> <%@page contenttype="text/html" pageencoding="utf-8"%> <!DOCTYPE html> <html> <head> <meta http-equiv="content-type" content="text/html; charset=utf-8"> </head> <body> <% // 取得.xml 檔 ApplicationContext context = new ClassPathXmlApplicationContext("beans-config.xml"); // 取得 Bean com.helloworld obj = (com.helloworld)context.getbean("mybean"); // 顯示訊息 out.print(" 訊息 1:" + obj.getmsg() + "<br/>"); out.print(" 訊息 2:" + obj.getmsg2() + "<br/>"); %> </body> </html> 12 6

7 Inversion of Control for Java 4 注入集合, 修改 HelloWorld 類別 package com; import java.util.arraylist; public class HelloWorld { private String mymsg; private ArrayList list; public void setmsg(string m) { this.mymsg = m; public String getmsg() { return this.mymsg; public ArrayList getlist() { return list; public void setlist(arraylist list) { this.list = list; 13 設定 beans-config.xml Inversion of Control for Java 5  <util:list id="mylist" list-class="java.util.arraylist"> <value>apple</value> <value>banana</value> </util:list>  <bean id="mybean" class="com.helloworld">  <property name="msg" value="hi!shadow" />  <property name="list" ref="mylist" /> </bean> 14 7

Inversion of Control for Java 6 JSP 程式 <%@page import="org.springframework.context.support.classpathxmlapplicationcontext"%> <%@page import="org.springframework.context.applicationcontext"%> <%@page contenttype="text/html" pageencoding="utf-8"%> <!

8 Inversion of Control for Java 6 JSP 程式 <%@page import="org.springframework.context.support.classpathxmlapplicationcontext"%> <%@page import="org.springframework.context.applicationcontext"%> <%@page contenttype="text/html" pageencoding="utf-8"%> <!DOCTYPE html> <html> <head> <meta http-equiv="content-type" content="text/html; charset=utf-8"> </head> <body> <% // 取得.xml 檔 ApplicationContext context = new ClassPathXmlApplicationContext("beans-config.xml"); // 取得 Bean com.helloworld obj = (com.helloworld)context.getbean("mybean"); // 從集合撈資料 for(object o:obj.getlist()) { String list_str = (String)o; out.print(list_str + "<br/>"); %> </body> </html> 15 Inversion of Control for Java 7 注入物件, 定義 Blog 類別, 修改 HelloWorld 類別 package com; public class Blog { private String blogowner; public String getblogowner() { return this.blogowner; public void setblogowner(string blogowner) { this.blogowner = blogowner; package com; public class HelloWorld { private String mymsg; private Blog myblog; public void setmsg(string m) { this.mymsg = m; public String getmsg() { return this.mymsg; public Blog getmyblog() { return this.myblog; public void setmyblog(blog myblog) { this.myblog = myblog; 16 8

9 Inversion of Control for Java 8 設定 beans-config.xml  <bean id="myblogobj" class="com.blog"> <property name="blogowner" value="shadow"/> </bean>  <bean id="mybean" class="com.helloworld">  <property name="msg" ><null /></property>  <property name="myblog" ref="myblogobj" /> </bean> 17 JSP 程式 Inversion of Control for Java 9 <%@page import="com.blog"%> <%@page import="org.springframework.context.support.classpathxmlapplicationcontext"%> <%@page import="org.springframework.context.applicationcontext"%> <%@page contenttype="text/html" pageencoding="utf-8"%> <!DOCTYPE html> <html> <head> <meta http-equiv="content-type" content="text/html; charset=utf-8"> </head> <body> <% // 取得.xml 檔 ApplicationContext context = new ClassPathXmlApplicationContext("beans-config.xml"); // 取得 Bean com.helloworld obj = (com.helloworld)context.getbean("mybean"); out.print(obj.getmsg());// 這裡其實是 NULL 值 Blog blog = (Blog)obj.getMyBlog(); out.print("<br/ >" + blog.getblogowner()); %> </body> </html> 18 9

10 Inversion of Control for Java 10 Constructor 注入, 修改 HelloWorld 類別 package com; public class HelloWorld { private String mymsg1; private String mymsg2; // 最好有無參數的建構子 public HelloWorld() { public HelloWorld(String msg1,string msg2) { this.mymsg1 = msg1; this.mymsg2 = msg2; public String getmsg() { return this.mymsg1 + this.mymsg2; 19 設定 beans-config.xml Inversion of Control for Java 11  <bean id="mybean" class="com.helloworld">  <constructor-arg index="0" value="hello!!" /> <constructor-arg index="1" value="shadow at 2011/06/20" />  </bean> 20 10

Inversion of Control for Java 12 JSP 程式 <%@page import="com.blog"%> <%@page import="org.springframework.context.support.classpathxmlapplicationcontext"%> <%@page import="org.springframework.context.applicationcontext"%> <%@page contenttype="text/html" pageencoding="utf-8"%> <!

11 Inversion of Control for Java 12 JSP 程式 import="com.blog"%> import="org.springframework.context.support.classpathxmlapplicationcontext"%> import="org.springframework.context.applicationcontext"%> contenttype="text/html" pageencoding="utf-8"%> <!DOCTYPE html> <html> <head> <meta http-equiv="content-type" content="text/html; charset=utf-8"> </head> <body> <% // 取得.xml 檔 ApplicationContext context = new ClassPathXmlApplicationContext("beans-config.xml"); // 取得 Bean com.helloworld obj = (com.helloworld)context.getbean("mybean"); out.print(obj.getmsg()); %> </body> </html> 21 11

IoC容器和Dependency Injection模式.doc

IoC容器和Dependency Injection模式.doc IoC Dependency Injection /Martin Fowler / Java Inversion of Control IoC Dependency Injection Service Locator Java J2EE open source J2EE J2EE web PicoContainer Spring Java Java OO.NET service component