写一个java的工作流使用案例

假设有一个请假申请的工作流，流程如下：

- 申请人提交请假申请单。
- 直属上级审批申请单，如果通过则流程结束；如果拒绝则返回给申请人修改。
- 部门经理审批申请单，如果通过则流程结束；如果拒绝则返回给申请人修改。
- 人事部门审批申请单，如果通过则流程结束；如果拒绝则返回给申请人修改。

下面是一个简单的Java工作流使用案例：

1. 定义请假申请单类

public class LeaveApplication {
    private String applicant; // 申请人
    private int days; // 请假天数
    private String reason; // 请假原因
    private String comment; // 审批意见
    private int status; // 审批状态

    // 省略 getter 和 setter 方法
}

2. 定义审批人角色枚举类

public enum Role {
    APPLICANT, // 申请人
    DIRECT_SUPERIOR, // 直属上级
    DEPARTMENT_MANAGER, // 部门经理
    HR_DEPARTMENT // 人事部门
}

3. 定义工作流类

public class Workflow {
    private Map<Role, User> users; // 角色与用户的映射
    private Map<Role, Role> approvalMap; // 审批流转图

    public Workflow(User applicant, User directSuperior, User departmentManager, User hrDepartment) {
        users = new HashMap<>();
        users.put(Role.APPLICANT, applicant);
        users.put(Role.DIRECT_SUPERIOR, directSuperior);
        users.put(Role.DEPARTMENT_MANAGER, departmentManager);
        users.put(Role.HR_DEPARTMENT, hrDepartment);

        approvalMap = new HashMap<>();
        approvalMap.put(Role.APPLICANT, Role.DIRECT_SUPERIOR);
        approvalMap.put(Role.DIRECT_SUPERIOR, Role.DEPARTMENT_MANAGER);
        approvalMap.put(Role.DEPARTMENT_MANAGER, Role.HR_DEPARTMENT);
    }

    public LeaveApplication startWorkflow(LeaveApplication application) {
        application.setStatus(0); // 设置审批状态为0，即待审批
        application.setComment(""); // 设置审批意见为空

        // 设置当前审批人为申请人
        Role currentRole = Role.APPLICANT;
        User currentUser = users.get(currentRole);

        while (currentRole != null && currentUser != null) {
            // 获取下一个审批人角色
            Role nextRole = approvalMap.get(currentRole);

            if (nextRole != null) {
                // 获取下一个审批人
                User nextUser = users.get(nextRole);

                // 向下一个审批人发送审批申请
                LeaveApplication approvalResult = nextUser.approve(application);

                // 更新申请单审批状态
                application.setStatus(approvalResult.getStatus());
                application.setComment(approvalResult.getComment());
            }

            // 设置当前审批人为下一个审批人
            currentRole = nextRole;
            currentUser = users.get(currentRole);
        }

        return application;
    }
}

4. 定义用户类

public class User {
    private String name;
    private Role role;

    public User(String name, Role role) {
        this.name = name;
        this.role = role;
    }

    public LeaveApplication approve(LeaveApplication application) {
        // 根据角色进行审批
        switch (role) {
            case DIRECT_SUPERIOR:
                // TODO: 审批逻辑
                break;
            case DEPARTMENT_MANAGER:
                // TODO: 审批逻辑
                break;
            case HR_DEPARTMENT:
                // TODO: 审批逻辑
                break;
        }

        return application;
    }
}

5. 使用工作流处理请假申请

public class Main {
    public static void main(String[] args) {
        // 创建用户
        User applicant = new User("申请人", Role.APPLICANT);
        User directSuperior = new User("直属上级", Role.DIRECT_SUPERIOR);
        User departmentManager = new User("部门经理", Role.DEPARTMENT_MANAGER);
        User hrDepartment = new User("人事部门", Role.HR_DEPARTMENT);

        // 创建工作流
        Workflow workflow = new Workflow(applicant, directSuperior, departmentManager, hrDepartment);

        // 创建请假申请单
        LeaveApplication application = new LeaveApplication();
        application.setApplicant("申请人");
        application.setDays(3);
        application.setReason("家中有事");

        // 开始工作流
        LeaveApplication result = workflow.startWorkflow(application);

        // 输出结果
        System.out.println("申请状态：" + result.getStatus());
        System.out.println("审批意见：" + result.getComment());
    }
}

以上是一个简单的Java工作流使用案例，实际的工作流可能会更加复杂，需要根据实际情况进行设计。