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Environment variables

The Chat Server API uses environment variables for sensitive configuration. These should be set before starting the server.

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JWT_SECRET

The JWT secret is used to sign authentication tokens. In production, always set a secure, random value.
The JWT_SECRET environment variable configures the secret key used for JWT token signing and verification (from Configuration.java:14). Default value: Base64-encoded string (insecure default for development only) Setting the variable: 
export JWT_SECRET="your-base64-encoded-secret-here"
Generate a secure Base64-encoded secret using:
openssl rand -base64 64

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JWT configuration constants

The following JWT-related constants are defined in Configuration.java:
  • JWT_EXPIRATION_MS: 1000 * 60 * 60 * 30 (30 days)
  • Token expiration time in milliseconds
  • Tokens issued will be valid for 30 days from creation

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Application properties

The server configuration is defined in application.properties. These settings control the Spring Boot application behavior.

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Database configuration

The server uses SQLite as the primary database (from application.properties:1-12): 
spring.application.name=server
spring.jpa.database-platform=org.hibernate.community.dialect.SQLiteDialect
spring.datasource.url=jdbc:sqlite:./main.db
spring.datasource.driver-class-name=org.sqlite.JDBC
spring.sql.init.mode=always
spring.jpa.hibernate.ddl-auto=update
spring.batch.jdbc.initialize-schema=always

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Database settings explained

  • spring.datasource.url: jdbc:sqlite:./main.db
    • Database file location (created in the current directory)
    • Change the path to customize the database location
  • spring.jpa.hibernate.ddl-auto: update
    • Automatically updates database schema based on entity changes
    • Use validate in production to prevent accidental schema changes
  • spring.sql.init.mode: always
    • Runs initialization scripts on startup

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SQLite performance optimizations

The application configures SQLite with performance optimizations via HikariCP connection pool: 
spring.datasource.hikari.connection-init-sql=\
  PRAGMA journal_mode=WAL;\
  PRAGMA synchronous=NORMAL;\
  PRAGMA cache_size=-10000;\
  PRAGMA temp_store=MEMORY;
  • journal_mode=WAL: Write-Ahead Logging for better concurrency
  • synchronous=NORMAL: Balanced durability and performance
  • cache_size=-10000: 10MB cache size (negative value = kilobytes)
  • temp_store=MEMORY: Use memory for temporary tables

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Database setup

The server supports two embedded databases:

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SQLite (default)

SQLite is configured as the default database and requires no additional setup.
1

Automatic database creation

When you start the server for the first time, SQLite will automatically create the main.db file in the server directory.
2

Schema initialization

Hibernate will automatically create tables based on JPA entity classes due to the ddl-auto=update setting.
3

Verify database

After starting the server, verify the database file exists:
ls -la main.db
The database file path is relative to where you start the server. If you run the server from different directories, multiple database files may be created.

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H2 Database (alternative)

H2 is included as a runtime dependency (build.gradle.kts:44) and can be used as an alternative in-memory database. To switch to H2, update application.properties: 
spring.datasource.url=jdbc:h2:mem:chatdb
spring.datasource.driver-class-name=org.h2.Driver
spring.jpa.database-platform=org.hibernate.dialect.H2Dialect
H2 in-memory databases lose all data when the server stops. Use file-based H2 (jdbc:h2:file:./chatdb) for persistence.

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Validation constraints

The server enforces validation rules defined in Configuration.java:8-10:
  • MIN_PASSWORD_LENGTH: 6 characters
  • MIN_USERNAME_LENGTH: 2 characters
  • MAX_USERNAME_LENGTH: 8 characters
These constants are used throughout the application for request validation.

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Security configuration

The server uses Spring Security with the following features:
  • Password encoding: BCrypt (configured in APIServerApplication.java:17-19)
  • JWT authentication: Token-based authentication with configurable expiration
  • Endpoint security: Protected endpoints require valid JWT tokens

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Server metadata

From Configuration.java:7:
  • SERVER_VERSION: 0.0.1
  • Used in API responses and OpenAPI documentation

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Custom configuration

To override default settings, create an application-local.properties file: 
# Custom database location
spring.datasource.url=jdbc:sqlite:/var/lib/chatserver/data.db

# Change server port
server.port=8080

# Enable debug logging
logging.level.org.uwgb.compsci330=DEBUG
Run the server with the local profile: 
./gradlew bootRun --args='--spring.profiles.active=local'

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