MockBoard

Local-first HTTP API mocks for development and testing
Java 21, Javalin, MapDB, Svelte

What It Is

MockBoard is a small local app for mocking HTTP APIs.

Run it, create a board, add mock rules, and call the generated /m/{boardId} URL from your app, tests, or scripts. Boards and rules are stored locally in MapDB, so there is no external database and no team account layer.

What It Does

• Creates local mock boards with optional display names.
• Serves mock endpoints from /m/{boardId}.
• Supports GET, POST, PUT, PATCH, DELETE, HEAD, and OPTIONS.
• Matches paths exactly or with single-segment * wildcards.
• Returns custom status codes, headers, JSON bodies, and response delays.
• Generates fake response values with {{template.keys}}.
• Shows incoming requests live in the UI through SSE.
• Keeps request logs per board while the app is running.

Usage

Start the app, open the UI, create a board, and add a mock rule.

Example mock rule:

• Method: GET
• Path: /api/users/*
• Status: 200
• Body:

{
  "id": "{{system.uuid}}",
  "name": "{{user.fullName}}",
  "email": "{{user.email}}"
}

Call it:

curl http://localhost:8000/m/{boardId}/api/users/123

Each call is logged in the board dashboard. If the rule body has templates, they are resolved on every request.

Dynamic Response Templates

Mock response bodies must be valid JSON. Template values can be placed inside JSON strings:

{
  "id": "{{system.uuid}}",
  "city": "{{address.city}}",
  "bio": "{{content.sentence}}"
}

Supported template keys:

Group	Keys
user	fullName, firstName, lastName, email, username, phoneNumber, avatar
address	full, city, street, zipCode, country, countryCode
content	char, word, sentence, paragraph
system	int, long, double, bool, uuid

Full key examples: {{user.email}}, {{address.city}}, {{content.paragraph}}, {{system.uuid}}.

Unknown templates render as [unknown: key]. Generated values are escaped for JSON strings.

Running Locally

Prerequisites:

• Java 21+
• Node 20+ if you are rebuilding the frontend
• Docker if you prefer Docker Compose

Build the frontend:

dev/scripts/build_frontend.sh

Build the Java jar:

dev/scripts/rebuild_java.sh

Build and run the jar:

dev/scripts/run_jar.sh

Manual run after building:

java -jar target/mockboard-0.4-beta.jar

Default URL:

http://localhost:8000

Docker:

docker compose up -d --build

Docker URL:

http://localhost:8888

Useful environment variables:

Variable	Default	Purpose
PORT	8000	HTTP server port
MBD_STORE_PATH	data/mockboard.db	Local MapDB file path
MBD_MAX_MOCK_RULES	1000	Max mock rules per board
MBD_MAX_WEBHOOKS	100	Max stored request log entries per board
MBD_VALIDATION_MOCK_MAX_ALLOWED_DELAY	10000	Max response delay in milliseconds
MBD_VALIDATION_MOCK_MAX_BODY_LENGTH	100000	Max JSON body length
MBD_VALIDATION_MOCK_MAX_PATH_LENGTH	1000	Max mock path length

The frontend source lives in src/frontend. The production build is served by Javalin from src/main/resources/static.

Contributing

No contributions are expected right now.

This is a personal local tool, not a product roadmap. Issues or notes are still useful if something is broken, but pull requests may sit untouched or be closed if they do not match how the tool is used.