设计模式-工厂模式

2020-08-29 阅读量

工厂模式指程序中甲组件需乙组件进行协助的时候,并不是直接创建乙组件的实例对象性,而是通过乙组件的工厂获得–该工厂可以生成某类型组件的对象. 在这种模式下,甲组件无须与乙组件以硬编码方式耦合在一起,而只需要与乙组件工厂耦合 .

反转依赖

public class UsbDiskWriter{
  pulic void save(){.......}
}

public class Business{
  UsbDiskWriter writer;
  public Business(){
    writer = new UsbDiskWriter();
  }
  public void save(){
    writer.save();
  }
}
//由于Bussines类的方法save()依赖于类UserDiskWriter,如果某天想换掉底层类为FloppyWriter , 则这个Business类没有办法重用 , 必须修改

  public class FloppyWriter{
    pulic void save(){.......}
 
 public class Business{
      FloppyWriter writer;
  public Business(){
    writer = new FloppyWriter();
  }
  public void save(){
    writer.save();
  }
}
  }
  
  //这种改变使得高层Bussiness类依赖于底层类 , 可以将两者抽象出一个接口 , 让Bussiness依赖于这个接口 :
  public interface IWriter{
    void save();
  }
  public class UsbDiskWriter implements IWriter{
    public void save(){........}
  }
  public class Bussniess{
    private IWriter writer;
    public Business(){
      writer = new UsbDiskWriter();
    }
     public void save(){
    writer.save();
  }
  }
//但是上述代码还是耦合性很强 , 源于Bbussiness类使用底层类时是直接创建底层类的实现对象;

工厂模式

public interface IWriter{
  void save();
}
  public class UsbDiskWriter implements IWriter{
    public void save(){........}
  }
public class FloppyWriter implements IWriter{
    public void save(){........}
  }
  
  //创建工厂
  public class WriterFactory{
    public IWriter getWriter(String name){
      if("UsbDiskWriter".equals(name){
        return new UsbDiskWriter();
      }
      else if("FloppyWriter".equals(name)){
        return new FloppyWriter();
        else{
          throw new IllegalArgumentException("参数不正确");
        }
      }
    }
  }
  
  public class business{
    public IWriter writer;
    public Business(String name ){
     writer = new WriterFactory().getWriter(name); 
    }
    public void save(){
      writer.save();
    }
  }

依赖注入

spring 内部实现工厂模式的IOC机制 , 实际上就是IOC容器 , 使用spring开发程序可以完全无理会被调用java类的实现 , 也无须主动创建和定位工厂;

  public interface IWriter{
    void save();
  }
  public class UsbDiskWriter implements IWriter{
    public void save(){........}
  }
  
public class FlobbyWriter implements IWriter{
    public void save(){........}
  }
  public class Bussniess{
    private IWriter writer;
    //设置值注入
  public void setWriter(IWriter writer){
    this.writer = writer;
  }
  //构造方法注入
  public Bussniess(IWriter writer){
    this.writer = writer;
  }
     public void save(){
    writer.save();
  }
  }