info

REST API server for a peer-review tracking system (school project data: peers, tasks, checks, friendships). Built on raw Jakarta Servlet API with manual JDBC - no ORM, no Spring.

Tech Stack

• Java 17, Jakarta Servlet API 5.0, embedded Tomcat 10.1
• PostgreSQL + HikariCP connection pool
• Jackson (jackson-datatype-jsr310 for LocalDate support)
• Lombok, JUnit 5, Mockito
• Maven, packaged as WAR (com.fersko.info.Main)

Notable Implementation Details

• No framework, no ORM. All HTTP routing is done via @WebServlet annotations; SQL is written by hand with PreparedStatement. The 4-layer stack (entity - repository - service - servlet) is wired manually via constructors, which makes Mockito injection straightforward.
• Generic service/repository interfaces. BaseRepository<T> and BaseService<T extends BaseDto> define the full CRUD contract once; all 4 entities implement it with zero code duplication in the interface layer.
• ResponseHandler utility class centralizes all servlet response logic: handleGetRequest, handleDeleteRequest, and sendJsonResponse are static helpers shared across all 4 servlets, keeping each servlet's HTTP methods to 3-5 lines.
• Recursive self-join mapping for Task. Task has a nullable parentTask of the same type. TaskMapper.toDto() recurses into itself for the parent, and TaskRepositoryImpl resolves the join via a LEFT JOIN tasks t1 ON t.parent_task = t1.pk_title query with aliased columns (parent_task_title, p_task_xp).
• Prefix-based column mapping in FriendRepositoryImpl. Both peers in a friends row are loaded from the same ResultSet using a getPeer(resultSet, "peer1")/getPeer(resultSet, "peer2") helper that builds column names dynamically from a prefix string.
• HikariCP configured statically via ConnectionManager - pool config is shared across all repository instances via a single static HikariConfig, with a secondary constructor accepting a HikariDataSource for test injection.

Quick Start

# requires PostgreSQL running on localhost:5433, database: postgres
# credentials in src/main/resources/application.properties

psql -U postgres -d postgres -f scriptsSql/tables.sql

./mvnw exec:java -Dexec.mainClass=com.fersko.info.Main

# API available at http://localhost:8080/data/{peers,tasks,checks,friends}
# GET /data/peers?id=1
# POST/PUT /data/checks  (JSON body - see DataforTestPostman/)
# DELETE /data/friends?id=3

./mvnw test