什么是职责链模式？职责链的实现

// 抽象处理者
abstract class Approver {
    protected Approver nextApprover;

    public void setNextApprover(Approver nextApprover) {
        this.nextApprover = nextApprover;
    }

    public abstract void processRequest(PurchaseRequest request);
}

// 具体处理者：部门经理
class DepartmentManager extends Approver {
    @Override
    public void processRequest(PurchaseRequest request) {
        if (request.getAmount() <= 5000) {
            System.out.println("部门经理审批了采购请求，金额：" + request.getAmount());
        } else if (nextApprover != null) {
            nextApprover.processRequest(request);
        } else {
            System.out.println("采购请求无法处理，金额：" + request.getAmount());
        }
    }
}

// 具体处理者：总监
class Director extends Approver {
    @Override
    public void processRequest(PurchaseRequest request) {
        if (request.getAmount() <= 10000) {
            System.out.println("总监审批了采购请求，金额：" + request.getAmount());
        } else if (nextApprover != null) {
            nextApprover.processRequest(request);
        } else {
            System.out.println("采购请求无法处理，金额：" + request.getAmount());
        }
    }
}

// 具体处理者：总经理
class CEO extends Approver {
    @Override
    public void processRequest(PurchaseRequest request) {
        System.out.println("总经理审批了采购请求，金额：" + request.getAmount());
    }
}

// 请求类
class PurchaseRequest {
    private int amount;
    private String purpose;

    public PurchaseRequest(int amount, String purpose) {
        this.amount = amount;
        this.purpose = purpose;
    }

    public int getAmount() {
        return amount;
    }

    public String getPurpose() {
        return purpose;
    }
}

// 客户端代码
public class ChainOfResponsibilityDemo {
    public static void main(String[] args) {
        DepartmentManager departmentManager = new DepartmentManager();
        Director director = new Director();
        CEO ceo = new CEO();

        departmentManager.setNextApprover(director);
        director.setNextApprover(ceo);

        PurchaseRequest request1 = new PurchaseRequest(4000, "购买办公用品");
        departmentManager.processRequest(request1); // 部门经理审批

        PurchaseRequest request2 = new PurchaseRequest(8000, "购买服务器");
        departmentManager.processRequest(request2); // 总监审批

        PurchaseRequest request3 = new PurchaseRequest(15000, "购买大型设备");
        departmentManager.processRequest(request3); // 总经理审批
    }
}