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Overview

The Library Management API uses PostgreSQL as its database and Hibernate/JPA for object-relational mapping. This guide covers all database-related configuration properties and connection setup.

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Database Connection

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Connection Properties

The following properties configure the PostgreSQL database connection:
PropertyTypeDescriptionExample
spring.datasource.urlStringPostgreSQL JDBC connection URLjdbc:postgresql://localhost:5432/library_db
spring.datasource.usernameStringDatabase usernamepostgres
spring.datasource.passwordStringDatabase passwordyourpassword
spring.datasource.driver-class-nameStringJDBC driver classorg.postgresql.Driver
Database credentials should never be hardcoded in application.properties. Use environment variables or external configuration management.

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Environment Variable Configuration

The application is configured to read database credentials from environment variables: 
spring.datasource.url=${db_url}
spring.datasource.username=${db_username}
spring.datasource.password=${db_password}
Required Environment Variables:
  • db_url - Full PostgreSQL JDBC connection string
  • db_username - Database user with appropriate permissions
  • db_password - Database user password

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Example Database URL Formats

export db_url="jdbc:postgresql://localhost:5432/library_db"
export db_username="postgres"
export db_password="admin123"

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JPA/Hibernate Configuration

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Hibernate Properties

PropertyValueDescription
spring.jpa.database-platformorg.hibernate.dialect.PostgreSQLDialectSpecifies PostgreSQL-specific SQL dialect
spring.jpa.hibernate.ddl-autocreate-dropDatabase schema generation strategy

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DDL Auto Modes

The spring.jpa.hibernate.ddl-auto property controls schema management:
  • Behavior: Creates schema at application startup, drops it at shutdown
  • Use Case: Development and testing
  • Warning: All data is lost when the application stops
  • Configured in: application.properties:13
  • Behavior: Updates schema to match entities without dropping data
  • Use Case: Development when you want to preserve data
  • Caution: May not handle all schema changes correctly
spring.jpa.hibernate.ddl-auto=update
  • Behavior: Validates schema matches entities, no modifications
  • Use Case: Production environments
  • Recommendation: Use with migration tools like Flyway or Liquibase
spring.jpa.hibernate.ddl-auto=validate
  • Behavior: No schema management by Hibernate
  • Use Case: Production with external schema management
spring.jpa.hibernate.ddl-auto=none
The default create-drop setting is only suitable for development. For production environments, use validate or none with proper database migration tools.

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Production Configuration Recommendations

For production deployments, consider these configuration changes:

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Connection Pool Settings

# HikariCP connection pool configuration
spring.datasource.hikari.maximum-pool-size=10
spring.datasource.hikari.minimum-idle=5
spring.datasource.hikari.connection-timeout=30000
spring.datasource.hikari.idle-timeout=600000
spring.datasource.hikari.max-lifetime=1800000

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JPA Production Settings

# Disable schema auto-generation
spring.jpa.hibernate.ddl-auto=validate

# Enable SQL logging in development only
spring.jpa.show-sql=false
spring.jpa.properties.hibernate.format_sql=false

# Performance optimizations
spring.jpa.properties.hibernate.jdbc.batch_size=20
spring.jpa.properties.hibernate.order_inserts=true
spring.jpa.properties.hibernate.order_updates=true

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SSL/TLS Connection

spring.datasource.url=jdbc:postgresql://your-host:5432/library_db?sslmode=require&ssl=true

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Troubleshooting

Error: Connection to localhost:5432 refusedSolutions:
  • Verify PostgreSQL is running: systemctl status postgresql
  • Check the port in your connection URL matches PostgreSQL configuration
  • Ensure firewall allows connections on port 5432
Error: FATAL: password authentication failed for userSolutions:
  • Verify environment variables are set correctly
  • Check PostgreSQL pg_hba.conf authentication settings
  • Ensure the user exists: psql -U postgres -c "\du"
Error: FATAL: database "library_db" does not existSolutions:
  • Create the database: CREATE DATABASE library_db;
  • Verify the database name in your connection URL
Error: Schema validation or creation failuresSolutions:
  • Check user has CREATE permissions
  • Review Hibernate logs for specific errors
  • Verify entity mappings are correct

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