访问者模式

<!--StartFragment-->

<!--StartFragment-->

<!--StartFragment-->

 

抽象访问者（Visitor）： 抽象类或者接口， 声明访问者可以访问哪些元素， 具体到程序中就是 visit方法的参数定义哪些对象是可以被访问的；

package VisitorPattern.visitor;

import VisitorPattern.element.CommonEmployee;
import VisitorPattern.element.ManagerEmployee;

//申明可以访问那些元素
public interface Visitor {

	public void visit(CommonEmployee employee);
	
	public void visit(ManagerEmployee employee);
	
}

package VisitorPattern.visitor;

public interface ShowVisitor extends Visitor{

	public String show();
}

 

package VisitorPattern.visitor;

public interface TongjiVisitor extends Visitor{

	public int getTotalSalary();
}

  

 

<!--StartFragment-->

具体访问者（ConcreteVisitor）: 访问者访问到一个类后该怎么干(哎， 这个别读歪了)， 要做什么事情；

package VisitorPattern.visitor;

import VisitorPattern.element.CommonEmployee;
import VisitorPattern.element.ManagerEmployee;

public class ShowVisitorImpl implements ShowVisitor{
	
	private String info = "";

	@Override
	public void visit(CommonEmployee employee) {
		
		info = info + "只关心普通员工的工作："+employee.getJob()+";";
	}

	@Override
	public void visit(ManagerEmployee employee) {
		
		info = info + "只关心经理的姓名:"+employee.getName()+";";
		
	}

	@Override
	public String show() {
		
		return info;
	}

}

 

package VisitorPattern.visitor;

import VisitorPattern.element.CommonEmployee;
import VisitorPattern.element.ManagerEmployee;

//用作统计
public class TongjiVisitorImpl implements TongjiVisitor{
	
	private int commonEmTotalSalary;
	
	private int managerEmTotalSalary;

	@Override
	public void visit(CommonEmployee employee) {
		commonEmTotalSalary = commonEmTotalSalary+employee.getSalary();
	}

	@Override
	public void visit(ManagerEmployee employee) {
		managerEmTotalSalary = managerEmTotalSalary + employee.getSalary();
	}
	
	public int getTotalSalary(){
		return commonEmTotalSalary + managerEmTotalSalary;
	}
	
	
}

 

<!--StartFragment-->

抽象元素（Element）： 接口或者抽象类， 声明接受那一类型的访问者访问， 程序上是通过 accept 方法

中的参数来定义；

<!--EndFragment-->

package VisitorPattern.element;

import VisitorPattern.visitor.Visitor;

public abstract class Employee {
	
	private String name;
	
	private String job; 
	
	private int salary;
	
	public Employee(String name,String job,int salary){
		this.name = name;
		this.job = job;
		this.salary = salary;
	}

	public abstract void accept(Visitor visitor);
	
	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}


	public String getJob() {
		return job;
	}


	public void setJob(String job) {
		this.job = job;
	}

	public int getSalary() {
		return salary;
	}

	public void setSalary(int salary) {
		this.salary = salary;
	}
	
}

 

<!--StartFragment-->

具体元素：（ConcreteElement）: 实现 accept 方法， 通常是 visitor.visit(this)， 基本上都形成了一

个套路了；

<!--EndFragment-->

package VisitorPattern.element;

import VisitorPattern.visitor.Visitor;

public class CommonEmployee extends Employee{


	public CommonEmployee(String name, String job,int salary) {
		super(name, job,salary);
	}

	@Override
	public void accept(Visitor visitor) {
		
		visitor.visit(this);
	}

}

 

package VisitorPattern.element;

import VisitorPattern.visitor.Visitor;

public class ManagerEmployee extends Employee{


	public ManagerEmployee(String name, String job,int salary) {
		super(name, job,salary);
	}

	@Override
	public void accept(Visitor visitor) {
		visitor.visit(this);
	}

}

 

<!--StartFragment-->

结构对象(ObjectStruture): 容纳多个不同类、 不同接口的容器， 比如 List、 Set、 Map 等， 在项目中，

一般很少抽象出来这个角色；

<!--EndFragment-->

客户端调用

package VisitorPattern;

import java.util.ArrayList;
import java.util.List;

import VisitorPattern.element.CommonEmployee;
import VisitorPattern.element.Employee;
import VisitorPattern.element.ManagerEmployee;
import VisitorPattern.visitor.ShowVisitor;
import VisitorPattern.visitor.TongjiVisitor;
import VisitorPattern.visitor.TongjiVisitorImpl;
import VisitorPattern.visitor.ShowVisitorImpl;

public class Client {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		
		ShowVisitor showVisitor = new ShowVisitorImpl();
		TongjiVisitor tongjiVisitor = new TongjiVisitorImpl();
		
		List<Employee> emList = new ArrayList<Employee>();
		
		emList.add(new CommonEmployee("张三","美工",2500));
		emList.add(new ManagerEmployee("王五","财务经理",7000));
		emList.add(new CommonEmployee("李四","架构师",6000));
		emList.add(new ManagerEmployee("赵六","IT经理",8000));
		
		for (Employee employee : emList) {
			employee.accept(showVisitor);
			employee.accept(tongjiVisitor);
		}
		
		System.out.println(tongjiVisitor.getTotalSalary());
		
		System.out.println(showVisitor.show());

	}

}

  

 

<!--EndFragment--><!--EndFragment-->