行为型模式 - 职责链模式 (Chain of Responsibility Pattern)
职责链模式是一种行为设计模式，它允许你将请求沿着处理者链进行传递，直到有一个处理者能够处理该请求为止。以下是几个职责链模式的经典案例。
在企业中，员工请假需要不同级别的领导进行审批，根据请假天数的不同，审批流程也有所不同。例如，请假天数小于 3 天，只需部门经理审批；请假天数在 3 - 7 天之间，需要部门经理和总监审批；请假天数大于 7 天，需要部门经理、总监和总经理审批。
// 抽象处理者类
abstract class Approver {protected Approver successor;public void setSuccessor(Approver successor) {this.successor = successor;}public abstract void processRequest(int days);
}// 部门经理类
class DepartmentManager extends Approver {@Overridepublic void processRequest(int days) {if (days < 3) {System.out.println("部门经理批准了 " + days + " 天的请假申请");} else if (successor != null) {successor.processRequest(days);}}
}// 总监类
class Director extends Approver {@Overridepublic void processRequest(int days) {if (days >= 3 && days < 7) {System.out.println("总监批准了 " + days + " 天的请假申请");} else if (successor != null) {successor.processRequest(days);}}
}// 总经理类
class GeneralManager extends Approver {@Overridepublic void processRequest(int days) {if (days >= 7) {System.out.println("总经理批准了 " + days + " 天的请假申请");}}
}// 客户端代码
public class LeaveApprovalSystem {public static void main(String[] args) {Approver departmentManager = new DepartmentManager();Approver director = new Director();Approver generalManager = new GeneralManager();departmentManager.setSuccessor(director);director.setSuccessor(generalManager);departmentManager.processRequest(2);departmentManager.processRequest(5);departmentManager.processRequest(10);}
}
再举个例子, 游戏中判断伤害, 分为物理伤害魔法伤害, 可以链式处理
// 抽象处理者类
abstract class AttackHandler {protected AttackHandler nextHandler;public void setNextHandler(AttackHandler nextHandler) {this.nextHandler = nextHandler;}public abstract void handleAttack(Attack attack);
}// 攻击类
class Attack {private String type;public Attack(String type) {this.type = type;}public String getType() {return type;}
}// 普通攻击处理者类
class NormalAttackHandler extends AttackHandler {@Overridepublic void handleAttack(Attack attack) {if ("normal".equals(attack.getType())) {System.out.println("处理普通攻击");} else if (nextHandler != null) {nextHandler.handleAttack(attack);}}
}// 魔法攻击处理者类
class MagicAttackHandler extends AttackHandler {@Overridepublic void handleAttack(Attack attack) {if ("magic".equals(attack.getType())) {System.out.println("处理魔法攻击");} else if (nextHandler != null) {nextHandler.handleAttack(attack);}}
}// 客户端代码
public class GameAttackHandling {public static void main(String[] args) {AttackHandler normalAttackHandler = new NormalAttackHandler();AttackHandler magicAttackHandler = new MagicAttackHandler();normalAttackHandler.setNextHandler(magicAttackHandler);Attack normalAttack = new Attack("normal");Attack magicAttack = new Attack("magic");normalAttackHandler.handleAttack(normalAttack);normalAttackHandler.handleAttack(magicAttack);}
}
