UserLookup - GraphQL Spring Boot Architecture

System Overview

flowchart TD subgraph ClientLayer[Clients] Web[Web App] Mobile[Mobile App] Postman[Postman/Testing] end subgraph APILayer[API Layer] GraphQL[GraphQL Endpoint] end subgraph ServiceLayer[Service Layer] Resolver[GraphQL Resolvers] Service[Business Services] end subgraph DataLayer[Data Layer] Repository[Spring Data JPA] H2[(H2 Database)] end ClientLayer -->|HTTP Requests| APILayer APILayer --> ServiceLayer ServiceLayer --> DataLayer

Key Features

Precise data queries with GraphQL
User and post management
Pagination and filtering support
Clean, extensible GraphQL schema
In-memory H2 database
Custom exception handling
Input validation
Relationship management

Technology Stack

Java 17

Language

Spring Boot 3

Framework

Spring GraphQL

API Layer

H2 Database

Storage

Detailed Architecture

classDiagram class User { +String id +String name +String email +List~Post~ posts } class Post { +String id +String title +String content +User author } class UserRepository { +findById(String id) User +findAll() List~User~ +findAll(Pageable pageable) Page~User~ } class PostRepository { +findByAuthorId(String authorId) List~Post~ } class UserService { +getUser(String id) User +getAllUsers() List~User~ +getUsersPaged(Pageable pageable) Page~User~ +createUser(UserInput input) User } class PostService { +getPostsByUser(String userId) List~Post~ +createPost(PostInput input) Post } class UserResolver { +posts(User user) List~Post~ } class Query { +getUser(String id) User +getAllUsers() List~User~ +getUsersPaged(int page, int size) Page~User~ +getPostsByUser(String userId) List~Post~ } class Mutation { +createUser(UserInput input) User +createPost(PostInput input) Post } User "1" -- "*" Post UserRepository ..> User PostRepository ..> Post UserService ..> UserRepository PostService ..> PostRepository UserResolver ..> PostService Query ..> UserService Query ..> PostService Mutation ..> UserService Mutation ..> PostService

Layered Architecture

GraphQL Layer

Schema definition and query/mutation handling

Resolver Layer

Data fetching and relationship resolution

Service Layer

Business logic and transaction management

Repository Layer

Data access and persistence

Model Layer

Entity definitions and relationships

API Examples

Get User by ID

query {
  getUser(id: "1") {
    id
    name
    email
    posts {
      id
      title
    }
  }
}

Get Paginated Users

query {
  getUsersPaged(page: 0, size: 2) {
    id
    name
    email
  }
}

Get Posts by User

query {
  getPostsByUser(userId: "1") {
    id
    title
    content
  }
}

Get All Users

query {
  getAllUsers {
    id
    name
    email
  }
}

Create User

mutation {
  createUser(input: { 
    name: "Alice Johnson", 
    email: "alice@example.com" 
  }) {
    id
    name
    email
  }
}

Create Post

mutation {
  createPost(input: { 
    title: "GraphQL with Spring", 
    content: "Content goes here", 
    authorId: "1" 
  }) {
    id
    title
    author {
      id
      name
    }
  }
}

Postman Testing

Test the API using Postman with either:

Raw JSON requests
Postman's native GraphQL support

JSON Request Example

{
  "query": "query { getUser(id: \"1\") { id name } }"
}

H2 Console

Access the in-memory database console at:

http://localhost:8080/h2-console

JDBC URL: jdbc:h2:mem:testdb

Username: sa (no password)

Setup Instructions

Quick Start

Clone the repository:

git clone https://github.com/PritiAryal/UserLookup.git
cd UserLookup

Build the project:
```
mvn clean install
```
Run the application:
```
mvn spring-boot:run
```
Access GraphQL endpoint at:
```
http://localhost:8080/graphql
```

UserLookup System Architecture