废话不多说，直接切入正题，本篇要讲的是 模板模式 + 责任链模式 实践。
该最佳实践本身就是一种对 责任链模式的增强，模板模式通过 父类 强耦合，预定义好 责任链 next 方法 的前后一些切面行为，优雅简洁。
先上示例，单独责任链模式 简单示例如下：
java
// 请假请求类
class LeaveRequest {
private String employeeName;
private int days;
public LeaveRequest(String employeeName, int days) {
this.employeeName = employeeName;
this.days = days;
}
public String getEmployeeName() {
return employeeName;
}
public int getDays() {
return days;
}
}
// 抽象处理者
abstract class Approver {
protected Approver nextApprover;
public Approver(Approver nextApprover) {
this.nextApprover = nextApprover;
}
public abstract void approve(LeaveRequest request);
}
// 具体处理者：组长，处理1-3天的请假
class TeamLeader extends Approver {
public TeamLeader(Approver nextApprover) {
super(nextApprover);
}
@Override
public void approve(LeaveRequest request) {
if (request.getDays() <= 3) {
System.out.println("组长批准了" + request.getEmployeeName() + "的" + request.getDays() + "天假期");
} else if (nextApprover != null) {
nextApprover.approve(request);
}
}
}
// 具体处理者：部门经理，处理4-7天的请假
class DepartmentManager extends Approver {
public DepartmentManager(Approver nextApprover) {
super(nextApprover);
}
@Override
public void approve(LeaveRequest request) {
if (request.getDays() > 3 && request.getDays() <= 7) {
System.out.println("部门经理批准了" + request.getEmployeeName() + "的" + request.getDays() + "天假期");
} else if (nextApprover != null) {
nextApprover.approve(request);
}
}
}
// 具体处理者：总经理，处理8天及以上的请假
class GeneralManager extends Approver {
public GeneralManager(Approver nextApprover) {
super(nextApprover);
}
@Override
public void approve(LeaveRequest request) {
if (request.getDays() > 7) {
System.out.println("总经理批准了" + request.getEmployeeName() + "的" + request.getDays() + "天假期");
} else if (nextApprover != null) {
nextApprover.approve(request);
}
}
}
// 演示类
public class LeaveApprovalDemo {
public static void main(String[] args) {
// 构建责任链
Approver generalManager = new GeneralManager(null);
Approver departmentManager = new DepartmentManager(generalManager);
Approver teamLeader = new TeamLeader(departmentManager);
// 创建请假请求
LeaveRequest request1 = new LeaveRequest("张三", 2);
LeaveRequest request2 = new LeaveRequest("李四", 5);
LeaveRequest request3 = new LeaveRequest("王五", 10);
// 处理请求
teamLeader.approve(request1);
teamLeader.approve(request2);
teamLeader.approve(request3);
}
}当需求增加，每个子类责任链都需要有额外的功能，比如 处理请假请求前，需要 看一下手表，就可以在父类抽取 出方法，子类只需要实现核心逻辑，前后切面逻辑父类通过模板模式预定义，不仅耦合性低，重用性也极高，如需要更改父类前后逻辑，直接进行重写即可，加上模板模式后，示例如下：
java
// 请假请求类
class LeaveRequest {
private String employeeName;
private int days;
private String reason;
public LeaveRequest(String employeeName, int days, String reason) {
this.employeeName = employeeName;
this.days = days;
this.reason = reason;
}
public String getEmployeeName() {
return employeeName;
}
public int getDays() {
return days;
}
public String getReason() {
return reason;
}
}
// 抽象处理者 - 结合了模板模式
abstract class Approver {
protected Approver nextApprover;
protected String approverTitle; // 审批者头衔
public Approver(String approverTitle, Approver nextApprover) {
this.approverTitle = approverTitle;
this.nextApprover = nextApprover;
}
// 模板方法：定义审批流程的骨架
public final void processRequest(LeaveRequest request) {
// 1. 前置处理
beforeApproval(request);
// 2. 核心审批逻辑（由子类实现）
boolean handled = handleApproval(request);
// 3. 后置处理
afterApproval(request, handled);
// 4. 如果当前处理者不能处理，传递给下一个
if (!handled && nextApprover != null) {
nextApprover.processRequest(request);
}
}
// 前置处理 - 模板中的固定步骤
protected void beforeApproval(LeaveRequest request) {
System.out.println("\n===== 开始处理 " + request.getEmployeeName() + " 的请假申请 =====");
System.out.println("请假天数: " + request.getDays() + "天");
System.out.println("请假原因: " + request.getReason());
System.out.println("当前审批者: " + approverTitle);
}
// 后置处理 - 模板中的固定步骤
protected void afterApproval(LeaveRequest request, boolean handled) {
if (handled) {
System.out.println(approverTitle + "已批准该请假申请");
System.out.println("===== " + request.getEmployeeName() + " 的请假申请处理完毕 =====");
} else {
System.out.println(approverTitle + "无法处理，将提交给上一级审批");
}
}
// 抽象方法：具体审批逻辑由子类实现
protected abstract boolean handleApproval(LeaveRequest request);
}
// 具体处理者：组长，处理1-3天的请假
class TeamLeader extends Approver {
public TeamLeader(Approver nextApprover) {
super("组长", nextApprover);
}
@Override
protected boolean handleApproval(LeaveRequest request) {
if (request.getDays() <= 3) {
// 组长特有的审批逻辑
System.out.println("组长审批：请假天数在权限范围内，直接批准");
return true;
}
return false;
}
}
// 具体处理者：部门经理，处理4-7天的请假
class DepartmentManager extends Approver {
public DepartmentManager(Approver nextApprover) {
super("部门经理", nextApprover);
}
@Override
protected boolean handleApproval(LeaveRequest request) {
if (request.getDays() > 3 && request.getDays() <= 7) {
// 部门经理特有的审批逻辑
System.out.println("部门经理审批：已核实工作安排，可批准请假");
return true;
}
return false;
}
}
// 具体处理者：总经理，处理8天及以上的请假
class GeneralManager extends Approver {
public GeneralManager(Approver nextApprover) {
super("总经理", nextApprover);
}
@Override
protected boolean handleApproval(LeaveRequest request) {
if (request.getDays() > 7) {
// 总经理特有的审批逻辑
System.out.println("总经理审批：已评估项目进度，批准长假申请");
return true;
}
return false;
}
}
// 演示类
public class EnhancedLeaveApprovalDemo {
public static void main(String[] args) {
// 构建责任链
Approver generalManager = new GeneralManager(null);
Approver departmentManager = new DepartmentManager(generalManager);
Approver teamLeader = new TeamLeader(departmentManager);
// 创建请假请求
LeaveRequest request1 = new LeaveRequest("张三", 2, "个人身体不适");
LeaveRequest request2 = new LeaveRequest("李四", 5, "家中有事需要处理");
LeaveRequest request3 = new LeaveRequest("王五", 10, "计划休年假旅游");
// 处理请求
teamLeader.processRequest(request1);
teamLeader.processRequest(request2);
teamLeader.processRequest(request3);
}
}