Spring Data REST Example

ja

Dependencies

This project uses the following libraries:

• Spring Boot Starter Data JPA: A starter to make accessing databases and integrating JPA easier.
• Spring Boot Starter Data REST: A starter to facilitate building RESTful APIs using Spring Data REST.
• Lombok: A library to automatically generate and omit boilerplate code in Java.
• H2 Database: A Java DBMS used as an in-memory database.
• Spring Boot Starter Test: A starter for testing Spring Boot applications.
• JUnit Platform Launcher: A library providing the launcher for JUnit5.
• Springdoc OpenAPI Starter Web MVC UI: A library to display OpenAPI specifications in HTML format.

About Spring Data REST Auto Endpoint Generation

Spring Data REST automatically exposes RESTful endpoints for your Spring Data repositories. This greatly simplifies the development of RESTful services by eliminating the need to manually create controllers for basic CRUD operations. Here’s how it works:

1. Repository Creation: Define a repository interface for your entity by extending CrudRepository, JpaRepository, or any other Spring Data repository interface.

   import org.springframework.data.jpa.repository.JpaRepository;
   import org.springframework.data.rest.core.annotation.RepositoryRestResource;
   
   @RepositoryRestResource
   public interface UserRepository extends JpaRepository<User, Long> {
   }

2. Entity Definition: Ensure you have an entity class that maps to a table in your database.

   import javax.persistence.Entity;
   import javax.persistence.GeneratedValue;
   import javax.persistence.GenerationType;
   import javax.persistence.Id;
   
   @Entity
   public class User {
       @Id
       @GeneratedValue(strategy = GenerationType.IDENTITY)
       private Long id;
       private String name;
   
       // getters and setters
   }

3. Running the Application: With minimal configuration, Spring Data REST will expose endpoints for the User entity, allowing you to interact with the data using HTTP methods. You can use GET, POST, PUT, DELETE requests against http://localhost:8080/users.

This automation reduces boilerplate code, enabling rapid development of data-driven applications. For instance, accessing http://localhost:8080/users will provide a list of users, and posting to the same endpoint will allow you to add new users.

spring.data.rest.base-path=/api

In this example, the base path for all Spring Data REST repositories would be changed to /api. So, the User entity endpoints would be accessible at http://localhost:8080/api/users.

For further customization and more advanced configurations, consult the official Spring Data REST documentation.

Entity Overview

The application is structured around two primary entities: Users and Posts. These entities are central to the data model and directly influence the RESTful API endpoints generated by Spring Data REST.

Users Entity

The Users entity encapsulates user information and establishes a relationship with the Posts entity. It includes:

• Fields:
  • id: Unique identifier for each user.
  • firstName: The first name of the user.
  • lastName: The last name of the user.
• Relationships:
  • posts: A collection of posts associated with the user, representing a one-to-many relationship.

Projections

Projections are used to customize the view of the data returned by the API. For example, the UserProjection provides a way to retrieve the full name of a user without exposing the password field.

package com.example.demo.projection;

import java.util.List;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.rest.core.config.Projection;

import com.example.demo.entity.Posts;
import com.example.demo.entity.Users;

@Projection(name = "without-password", types = { Users.class })
public interface UserProjection {
    @Value("#{target.firstName} #{target.lastName}")
    public String getFullName();

    public List<Posts> getPosts();
}

This projection can be accessed by appending ?projection=without-password to the API endpoint, e.g., http://localhost:8080/api/users?projection=without-password.

Posts Entity

The Posts entity represents individual posts made by users. It comprises:

• Fields:
  • id: Unique identifier for each post.
  • title: The title of the post.
  • content: The content of the post.
  • published: A boolean indicating whether the post is published.
• Relationships:
  • user: A reference to the user who created the post, establishing a many-to-one relationship back to the Users entity.

These entities form the backbone of the application's data model, enabling the creation of intuitive and functional RESTful APIs for managing user profiles and their associated posts.

Repository Overview

The application employs two primary repositories, UsersRepository and PostsRepository, to manage data persistence for the Users and Posts entities. These repositories inherit basic CRUD operations from Spring Data JPA, facilitating seamless data access and manipulation.

UsersRepository

Manages the persistence of Users entities, supporting standard CRUD operations.

PostsRepository

Handles the persistence of Posts entities, offering CRUD operations along with a method to filter posts by their published status.

These repositories serve as the foundation for the RESTful APIs generated by Spring Data REST, streamlining data access and manipulation processes.

boot

./gradlew bootRun
# or windows
gradlew.bat bootRun

see database

http://localhost:8080/h2-console

Driver Class	org.h2.Driver
JDBC URL	jdbc:h2:mem:testdb
User Name	sa
Password

call api

example

request

curl --location 'http://localhost:8080/users' \
--header 'Accept: application/hal+json'

response

{
    "_embedded": {
        "users": [
            {
                "name": "James Smith",
                "_links": {
                    "self": {
                        "href": "http://localhost:8080/users/1"
                    },
                    "users": {
                        "href": "http://localhost:8080/users/1"
                    },
                    "posts": {
                        "href": "http://localhost:8080/users/1/posts"
                    }
                }
            },
            {
                "name": "Christopher Anderson",
                "_links": {
                    "self": {
                        "href": "http://localhost:8080/users/2"
                    },
                    "users": {
                        "href": "http://localhost:8080/users/2"
                    },
                    "posts": {
                        "href": "http://localhost:8080/users/2/posts"
                    }
                }
            }
        ]
    },
    "_links": {
        "self": {
            "href": "http://localhost:8080/users?page=0&size=20"
        },
        "profile": {
            "href": "http://localhost:8080/profile/users"
        }
    },
    "page": {
        "size": 20,
        "totalElements": 2,
        "totalPages": 1,
        "number": 0
    }
}

For more details, see http://localhost:8080/swagger-ui/index.html

use postman

1. copy url

http://localhost:8080/v3/api-docs

2. click import & paste url

3. click import