A Java implementation of the State design pattern for approval workflows. The project models a document approval pipeline where behavior changes based on the document's current state: DRAFT, REVIEW, REJECTED, or APPROVED.

The goal is to keep workflow rules encapsulated inside state classes instead of scattering conditional logic throughout the application.

Approval workflows often need to enforce rules such as:

• Draft documents can be edited and submitted for review.
• Documents under review cannot be edited.
• Rejected documents can be revised and resubmitted.
• Approved documents are final and cannot be changed.

This project demonstrates how those rules can be implemented cleanly with object-oriented design. The Document class delegates each action to the active state object, and each state decides whether the action is allowed, blocked, or should trigger a transition.

• State-driven workflow behavior using the State pattern
• Clear separation between workflow context and state-specific rules
• Prevention of invalid transitions
• Audit logging with timestamps in workflow.log
• Console-based demonstration scenario
• Lightweight transition regression test

DRAFT -> REVIEW -> APPROVED
           |
           v
        REJECTED -> REVIEW

state-driven-workflow-engine/
├── Main.java
├── README.md
├── scenario.txt
├── state/
│   ├── ApprovedState.java
│   ├── DraftState.java
│   ├── RejectedState.java
│   ├── ReviewState.java
│   └── State.java
├── tests/
│   └── WorkflowTest.java
├── util/
│   └── LoggerUtil.java
└── workflow/
    └── Document.java

The implementation uses four main concepts:

The Document starts in DraftState. Public actions such as edit(), submit(), approve(), and reject() are delegated to the current state.

When an action causes a valid transition, the state returns the next state. The Document applies the transition internally, keeping direct state changes hidden from external callers.

Compile the source files:

javac Main.java workflow/*.java state/*.java util/*.java

Run the demo workflow:

java Main

Compile the application and test classes into an output directory:

javac -d out Main.java workflow/*.java state/*.java util/*.java tests/*.java

Run the transition test:

java -cp out tests.WorkflowTest

The included demo models a company policy approval flow:

1. An employee creates a policy document.
2. The employee edits the draft.
3. The employee submits it for review.
4. The manager rejects it.
5. The employee revises and resubmits it.
6. The manager approves it.
7. Further edits are blocked after approval.

Workflow activity is written to workflow.log with timestamps. Logged events include document creation, successful state transitions, approvals, rejections, edits, resubmissions, and blocked actions.

Example:

[2026-06-28 23:32:33] Document approved from REVIEW state.

• Add a formal build tool such as Maven or Gradle
• Add JUnit-based automated tests
• Support role-based access control
• Persist workflow history in a database
• Add a web or desktop interface

Archita Thakur
Computer Science & AI Student