Chain of Responsibility Design Pattern in Java

Beginner-friendly Java example

Focus on the roles in the example first. The pattern becomes easier when you can identify the sender, receiver, context, state, or strategy involved.

// Step 1: Define the request
class LeaveRequest {
    private final String employeeName;
    private final int days;

    public LeaveRequest(String employeeName, int days) {
        this.employeeName = employeeName;
        this.days = days;
    }

    public String getEmployeeName() { return employeeName; }
    public int getDays() { return days; }
}

// Step 2: Define the handler interface
interface LeaveApprover {
    void approveLeave(LeaveRequest leaveRequest);
}

// Step 3: Implement concrete handlers
class TeamLead implements LeaveApprover {
    private static final int MAX_LEAVES_ALLOWED = 2;
    private LeaveApprover nextApprover;

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

    public void approveLeave(LeaveRequest request) {
        if (request.getDays() <= MAX_LEAVES_ALLOWED) {
            System.out.println("Approved by Team Lead for "
                    + request.getEmployeeName());
        } else if (nextApprover != null) {
            nextApprover.approveLeave(request);
        }
    }
}

class Manager implements LeaveApprover {
    private static final int MAX_LEAVES_ALLOWED = 5;
    private LeaveApprover nextApprover;

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

    public void approveLeave(LeaveRequest request) {
        if (request.getDays() <= MAX_LEAVES_ALLOWED) {
            System.out.println("Approved by Manager for "
                    + request.getEmployeeName());
        } else if (nextApprover != null) {
            nextApprover.approveLeave(request);
        }
    }
}

class DepartmentHead implements LeaveApprover {
    private static final int MAX_LEAVES_ALLOWED = 10;

    public void approveLeave(LeaveRequest request) {
        if (request.getDays() <= MAX_LEAVES_ALLOWED) {
            System.out.println("Approved by Department Head for "
                    + request.getEmployeeName());
        } else {
            System.out.println("Leave denied for "
                    + request.getEmployeeName());
        }
    }
}

// Step 4: Construct and use the chain
public class ChainOfResponsibilityExample {
    public static void main(String[] args) {
        TeamLead teamLead = new TeamLead();
        Manager manager = new Manager();
        DepartmentHead departmentHead = new DepartmentHead();

        teamLead.setNextApprover(manager);
        manager.setNextApprover(departmentHead);

        teamLead.approveLeave(new LeaveRequest("John", 3));
        teamLead.approveLeave(new LeaveRequest("Alice", 7));
        teamLead.approveLeave(new LeaveRequest("Bob", 12));
    }
}

// Flow: Team Lead -> Manager -> Department Head

Benefits and trade-offs

Real-time use cases

• Employee leave approval
• Authentication filters
• Spring Security chains
• Servlet interceptor chains
• Support ticket escalation