Likes & Reactions System

Relevant source files

The following files were used as context for generating this wiki page:

• src/main/java/org/example/coding_convention/likes/controller/LikeController.java
• src/main/java/org/example/coding_convention/likes/service/LikeService.java
• src/main/java/org/example/coding_convention/likes/model/Like.java
• src/main/java/org/example/coding_convention/likes/repository/LikeRepository.java
• src/main/java/org/example/coding_convention/project/model/Project.java
• src/main/java/org/example/coding_convention/project/model/ProjectDto.java
• src/main/resources/data.sql

The Likes & Reactions System in PhanesEditor-BE provides a mechanism for users to express interest in specific coding projects. It functions as a "toggle" system where a user can either add or remove a like from a project with a single action. This system is integrated with the project search and discovery features, allowing users to see the popularity of projects through a de-normalized like count.

The system is built using Spring Boot, Spring Data JPA, and MariaDB. It ensures data integrity through transactional operations that synchronize the individual Like records with the aggregate like_count stored on the Project entity.

Sources: src/main/java/org/example/coding_convention/likes/service/LikeService.java, src/main/java/org/example/coding_convention/project/model/Project.java:58-72

System Architecture and Logic

The system follows a standard Controller-Service-Repository pattern. The core logic resides in the LikeService, which determines whether to create or delete a Like record based on the current state of the database.

Logic Flow: Toggle Mechanism

When a user requests to "like" a project, the system performs the following steps:

1. Identifies the User from the authentication principal.
2. Retrieves the target Project by its index.
3. Checks if a Like record already exists for that specific User-Project pair.
4. If exists: Deletes the Like record and decrements the Project.like_count.
5. If not exists: Creates a new Like record and increments the Project.like_count.

The diagram shows the decision logic for the toggle mechanism within a single transactional unit.
Sources: src/main/java/org/example/coding_convention/likes/service/LikeService.java:18-34

Data Model and Schema

The system utilizes a dedicated likes table to manage many-to-many relationships between users and projects, while maintaining a de-normalized count in the project table for performance during searches.

Entity Relationships

The Like entity serves as a join table linking User and Project. Each Like record is unique to a specific user and project.

The ER diagram illustrates the relationship between users, projects, and the likes that connect them.
Sources: src/main/java/org/example/coding_convention/likes/model/Like.java, src/main/resources/data.sql:72-78

Database Schema Details

Table	Column	Type	Constraints	Description
likes	idx	INT	PRIMARY KEY, AUTO_INCREMENT	Unique identifier for the like record.
likes	user_idx	INT	FOREIGN KEY (users.idx)	Reference to the user who liked the project.
likes	project_idx	INT	FOREIGN KEY (project.idx)	Reference to the project being liked.
project	like_count	INT	DEFAULT 0, NOT NULL	De-normalized counter for total likes.

Sources: src/main/resources/data.sql:57-78, src/main/java/org/example/coding_convention/project/model/Project.java:58-60

API Implementation

The system exposes a single endpoint to handle the toggling of likes.

Endpoint Specification

• URL: /like/{idx}
• Method: GET
• Authentication: Requires a JWT (Bearer Auth).
• Path Variable: idx (Integer) - The unique identifier of the project.

@GetMapping("/{idx}")
public BaseResponse likes(@AuthenticationPrincipal UserDto.AuthUser authUser, @PathVariable Integer idx) {
    likeService.likes(authUser, idx);
    return BaseResponse.success("완료");
}

Sources: src/main/java/org/example/coding_convention/likes/controller/LikeController.java:18-23

Response Structure

The system uses a BaseResponse wrapper for all operations.

Field	Type	Description
success	Boolean	Indicates if the toggle operation was successful.
message	String	Returns "완료" (Completed) upon success.
results	Object	Null for this operation.

Sources: src/main/java/org/example/coding_convention/common/model/BaseResponse.java, src/main/java/org/example/coding_convention/likes/controller/LikeController.java:21

Integration with Project Search

The like_count is a critical field in the ProjectSearchRes DTO, which is used when users search for or list projects.

Search Result DTO

The ProjectDto.ProjectSearchRes includes the likeCount to provide immediate feedback on project popularity without requiring additional joins or count queries during list rendering.

public static ProjectDto.ProjectSearchRes from(Project entity) {
    return ProjectSearchRes.builder()
            .idx(entity.getIdx())
            .name(entity.getProjectName())
            .creator(entity.getUser().getNickname())
            .language(entity.getLanguage().toString())
            .description(entity.getDescription())
            .likeCount(entity.getLikeCount()) // Integrated like count
            .build();
}

Sources: src/main/java/org/example/coding_convention/project/model/ProjectDto.java:125-136

Summary

The Likes & Reactions System provides a streamlined, transactional way for users to interact with projects. By combining a relational Like record for tracking specific user actions with a de-normalized like_count on the Project entity, the system achieves both data integrity and high-performance read access for project discovery.