设计者模式(22) -- 访问者模式

迷南。 2023-06-21 08:59 2阅读 0赞

### 文章目录 ###

*  需求
 *   *  传统方式的问题分析
 *  访问者模式
 *   *  基本介绍
     *  访问者模式的原理类图
     *  使用访问者模式实现歌手测评需求
     *   *  类图:
         *  代码:
         *  总结
 *  访问者模式的注意事项和细节

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70]

# 需求 #

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 1]

## 传统方式的问题分析 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 2]

# 访问者模式 #

## 基本介绍 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 3]

## 访问者模式的原理类图 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 4]

## 使用访问者模式实现歌手测评需求 ##

### 类图: ###

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 5]

### 代码: ###

Person

public abstract class Person { 
    	
    	//提供一个方法，让访问者可以访问
    	public abstract void accept(Action action);
    }

Woman

//说明
    //1. 这里我们使用到了双分派, 即首先在客户端程序中，将具体状态作为参数传递Woman中(第一次分派)
    //2. 然后Woman 类调用作为参数的 "具体方法" 中方法getWomanResult, 同时将自己(this)作为参数
    // 传入，完成第二次的分派
    public class Woman extends Person{ 
    
    	@Override
    	public void accept(Action action) { 
    		// TODO Auto-generated method stub
    		action.getWomanResult(this);
    	}
    }

Man

public class Man extends Person { 
    
    	@Override
    	public void accept(Action action) { 
    		// TODO Auto-generated method stub
    		action.getManResult(this);
    	}
    
    }

Action

public abstract class Action { 
    	
    	//得到男性 的测评
    	public abstract void getManResult(Man man);
    	
    	//得到女的 测评
    	public abstract void getWomanResult(Woman woman);
    }

Success

public class Success extends Action { 
    
    	@Override
    	public void getManResult(Man man) { 
    		// TODO Auto-generated method stub
    		System.out.println(" 男人给的评价该歌手很成功 !");
    	}
    
    	@Override
    	public void getWomanResult(Woman woman) { 
    		// TODO Auto-generated method stub
    		System.out.println(" 女人给的评价该歌手很成功 !");
    	}
    }

Fail

public class Fail extends Action { 
    
    	@Override
    	public void getManResult(Man man) { 
    		// TODO Auto-generated method stub
    		System.out.println(" 男人给的评价该歌手失败 !");
    	}
    
    	@Override
    	public void getWomanResult(Woman woman) { 
    		// TODO Auto-generated method stub
    		System.out.println(" 女人给的评价该歌手失败 !");
    	}
    
    }

Wait

public class Wait extends Action { 
    
    	@Override
    	public void getManResult(Man man) { 
    		// TODO Auto-generated method stub
    		System.out.println(" 男人给的评价是该歌手待定 ..");
    	}
    
    	@Override
    	public void getWomanResult(Woman woman) { 
    		// TODO Auto-generated method stub
    		System.out.println(" 女人给的评价是该歌手待定 ..");
    	}
    }

ObjectStructure

//数据结构，管理很多人（Man , Woman）
    public class ObjectStructure { 
    
    	//维护了一个集合
    	private List<Person> persons = new LinkedList<>();
    	
    	//增加到list
    	public void attach(Person p) { 
    		persons.add(p);
    	}
    	//移除
    	public void detach(Person p) { 
    		persons.remove(p);
    	}
    	
    	//显示测评情况
    	public void display(Action action) { 
    		for(Person p: persons) { 
    			p.accept(action);
    		}
    	}
    }

Client

public class Client { 
    
    	public static void main(String[] args) { 
    		// TODO Auto-generated method stub
    		//创建ObjectStructure
    		ObjectStructure objectStructure = new ObjectStructure();
    		
    		objectStructure.attach(new Man());
    		objectStructure.attach(new Woman());
    		
    		
    		//成功
    		Success success = new Success();
    		objectStructure.display(success);
    		
    		System.out.println("===============");
    		Fail fail = new Fail();
    		objectStructure.display(fail);
    		
    		System.out.println("=======给的是待定的测评========");
    		
    		Wait wait = new Wait();
    		objectStructure.display(wait);
    	}
    }

运行结果:  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 6]

### 总结 ###

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 7]

# 访问者模式的注意事项和细节 #

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 8]

--------------------

完

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