Ioc的推荐实现方式

Ioc（Inversion of Control）中文翻译为“控制反转”，Ioc的抽象概念是依赖关系转移，即“程序与实现必须依赖于抽象”。 控制反转最常见的实现方式就是依赖注入（Depedency Injection），依赖注入的含义是：保留抽象接口，让组件依赖抽象接口，当组件要与其他对象发生依赖关系时，通过抽象接口来注入依赖的实际对象。 在解说Ioc之前，先看一个设计的例子：
设计一个保存数据到软盘、USB设备的程序。   一、反面例子，没有使用Ioc   /** * Created by IntelliJ IDEA. * User: leizhimin * Date: 2007-9-25 * Time: 11:13:32 * * */ public class FloppyWriter {     public void saveToDevice() {         System.out.println("FloppyWriter.saveToDevice(): Floppy!");     } }   /** * Created by IntelliJ IDEA. * User: leizhimin * Date: 2007-9-25 * Time: 11:14:25 * * */ public class BusinessObject {     private FloppyWriter floppyWriter;       public FloppyWriter getFloppyWriter() {         return floppyWriter;     }       public void setFloppyWriter(FloppyWriter floppyWriter) {         this.floppyWriter = floppyWriter;     }       public void save() {         System.out.println("----BusinessObjectsave()....");         floppyWriter.saveToDevice();         System.out.println("----BusinessObjectsave()....");     } }   /** * Created by IntelliJ IDEA. * User: leizhimin * Date: 2007-9-25 * Time: 1:15:17 * * */ public class Client {     public static void main(String args[]){         //         BusinessObject businessObject=new BusinessObject();         FloppyWriter floppyWriter=new FloppyWriter();         businessObject.setFloppyWriter(floppyWriter);           //         businessObject.save();     } }   二、Ioc的实现推荐实现方式：setter方式   /** * Created by IntelliJ IDEA. * User: leizhimin * Date: 2007-9-25 * Time: 11:38:32 * */ public interface IDeviceWriter {     public void saveToDevice(); }   /** * Created by IntelliJ IDEA. * User: leizhimin * Date: 2007-9-25 * Time: 11:44:46 * , */ public class FloppyWriter implements IDeviceWriter{     public void saveToDevice() {         System.out.println("FloppyWriter.saveToDevice(): Floppy!");     } }   /** * Created by IntelliJ IDEA. * User: leizhimin * Date: 2007-9-25 * Time: 11:44:57 * ,USB */ public class USBWriter implements IDeviceWriter{     public void saveToDevice() {         System.out.println("USBWriter.saveToDevice(): USB!");     } }     /** * Created by IntelliJ IDEA. * User: leizhimin * Date: 2007-9-25 * Time: 11:40:24 * */ public class BusinessObject {     private IDeviceWriter writer;       public IDeviceWriter getWriter() {         return writer;     }       public void setWriter(IDeviceWriter writer) {         this.writer = writer;     }       /**      *      */     public void save(){         System.out.println("----BusinessObjectsave()....");         writer.saveToDevice();         System.out.println("----BusinessObjectsave()....");     } }   /** * Created by IntelliJ IDEA. * User: leizhimin * Date: 2007-9-25 * Time: 11:51:09 * */ public class Client {     public static void main(String args[]){         //         IDeviceWriter floppyWriter=new FloppyWriter();         IDeviceWriter usbWriter=new USBWriter();           //         BusinessObject businessObject1=new BusinessObject();         BusinessObject businessObject2=new BusinessObject();           //         businessObject1.setWriter(floppyWriter);         businessObject1.save();           System.out.println();           //         businessObject2.setWriter(usbWriter);         businessObject2.save();     } }   三、Ioc的实现推荐实现方式：constructor方式 在setter方式基础上修改，IDeviceWriter、FloppyWriter、USBWriter不变，BusinessObject和 Client类修改为：   /** * Created by IntelliJ IDEA. * User: leizhimin * Date: 2007-9-25 * Time: 11:32:03 * */ public class BusinessObject {     private IDeviceWriter writer;       public BusinessObject() {     }       public BusinessObject(IDeviceWriter writer) {         this.writer = writer;     }       public IDeviceWriter getWriter() {         return writer;     }       public void setWriter(IDeviceWriter writer) {         this.writer = writer;     }       /**      *      */     public void save() {         System.out.println("----BusinessObjectsave()....");         writer.saveToDevice();         System.out.println("----BusinessObjectsave()....");    } }   /** * Created by IntelliJ IDEA. * User: leizhimin * Date: 2007-9-25 * Time: 11:35:52 * */ public class Client {     public static void main(String args[]){         //         IDeviceWriter floppyWriter=new FloppyWriter();         IDeviceWriter usbWriter=new USBWriter();           //         BusinessObject businessObject1=new BusinessObject(floppyWriter);         BusinessObject businessObject2=new BusinessObject(usbWriter);           //         businessObject1.save();         System.out.println();         businessObject2.save();     } }   两种实现方式执行的结果相同： ----开始调用业务组件BusinessObject的save()方法....
调用FloppyWriter.saveToDevice()方法: 保存到了Floppy设备上!
----结束调用业务组件BusinessObject的save()方法.... ----开始调用业务组件BusinessObject的save()方法....
调用USBWriter.saveToDevice()方法: 保存到了USB设备上!
----结束调用业务组件BusinessObject的save()方法.... Process finished with exit code 0

本文转自 leizhimin 51CTO博客，原文链接：http://blog.51cto.com/lavasoft/43900，如需转载请自行联系原作者
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