Java设计模式：访问者模式，同一数据对象，不同访问者索取目的不同

绝地灬酷狼 2023-11-23 07:09 161阅读 0赞

/**
     * 员工接受不同部门的数据访问。 
     * 但是不同部门访问该名员工获取的数据不相同。
     * 
     * @author zhangfly
     *
     * @param <T>
     */
    public abstract class Employee<T> {
    
    	public abstract void accept(Department department);
    
    	public String getName() {
    		return null;
    	}
    
    	public int getYear() {
    		return 0;
    	}
    
    	public T getInfo() {
    		return null;
    	}
    }

/**
     * 不同部门访问同一员工，访问的目的不同，获取的员工数据不同。
     * 
     * @author zhangfly
     *
     */
    public abstract class Department {
    	public abstract void visit(Employee employee);
    }

public class EmployeeImpl extends Employee {
    	private String name = "zhang";
    	private int year = 2019;
    
    	@Override
    	public void accept(Department department) {
    		department.visit(this);
    	}
    
    	@Override
    	public String getName() {
    		return name;
    	}
    
    	@Override
    	public int getYear() {
    		return year;
    	}
    }

/**
     * A，不同部门之一。
     * 
     * @author zhangfly
     *
     */
    public class DepartmentA extends Department {
    	@Override
    	public void visit(Employee employee) {
    		System.out.println("Department A 访问-> " + employee.getName());
    	}
    }

/**
     * B，不同部门之一。
     * 
     * @author zhangfly
     *
     */
    public class DepartmentB extends Department {
    	@Override
    	public void visit(Employee employee) {
    		System.out.println("Department B 访问-> " + employee.getYear());
    	}
    }

public class Test {
    	public Test() {
    		Employee employee = new EmployeeImpl();
    		Department departmentA = new DepartmentA();
    		Department departmentB = new DepartmentB();
    
    		departmentA.visit(employee);
    		departmentB.visit(employee);
    		System.out.println("###分割线###");
    		employee.accept(departmentB);
    		employee.accept(departmentA);
    	}
    
    	public static void main(String[] args) {
    		new Test();
    	}
    }

输出：

Department A 访问-> zhang
    Department B 访问-> 2019
    ###分割线###
    Department B 访问-> 2019
    Department A 访问-> zhang

附另外一篇访问者模式文：[https://blog.csdn.net/zhangphil/article/details/88742963][https_blog.csdn.net_zhangphil_article_details_88742963]

[https_blog.csdn.net_zhangphil_article_details_88742963]: https://blog.csdn.net/zhangphil/article/details/88742963