You don’t need every property—you need to understand what problem each category solves. Here’s the clean version:

`application.properties` — what it really is¶

This file = runtime configuration

Not build (that’s pom.xml) Not code (that’s Java)

This controls how your app behaves when it runs.

Core structure (think in buckets)¶

1. Server (how your app is exposed)¶

server.port=8080
server.servlet.context-path=/app

port → where app runs
context-path → base URL

If this is wrong → app runs but you can’t reach it.

2. Application identity¶

spring.application.name=demo

Used in:

logs
microservices (service discovery)

3. Database (most critical in real apps)¶

spring.datasource.url=jdbc:mysql://localhost:3306/db
spring.datasource.username=root
spring.datasource.password=pass

This answers:

Where is my data and how do I connect?

Wrong config → app starts but crashes on DB access.

4. JPA / Hibernate (how DB is handled)¶

spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true

ddl-auto → schema behavior (create/update/none)
show-sql → logs queries

If you don’t understand this, you’ll destroy or mismatch your database.

5. Logging (visibility)¶

logging.level.root=INFO
logging.level.org.springframework=DEBUG

Controls how much you see.

Too little → blind Too much → noise

6. Profiles (environment switching)¶

spring.profiles.active=dev

Lets you switch configs:

dev
test
prod

Without this → you’ll hardcode everything and regret it later.

7. Custom properties (your own config)¶

app.feature.enabled=true
app.api.key=xyz

Used in your code via:

@Value("${app.api.key}")

This is how you avoid hardcoding values.

What you’re probably missing¶

Most beginners treat this file like:

“random place to dump configs”

Wrong.

Each property should answer:

What system am I configuring?
What happens if this value changes?

If you can’t answer that → you’re guessing.

Mental model¶

Think in 3 layers:

Server → how app runs
Infrastructure → DB, external systems
Behavior → logging, features, profiles

spring.application.name=demo

for actuator¶

management.endpoints.web.exposure.include=health,info,beans management.info.env.enabled=true info.app.name=Demo info.app.version=1.0 info.app.description=Demo application for spring

for Logging¶

logging.level.org=INFO¶

logging.level.org.springframework=DEBUG¶

logging.level.org.springframework.web=ERROR¶

logging.level.org.hibernate=TRACE¶

spring.datasource.url=jdbc:postgresql://host.docker.internal:5432/claims?currentSchema=claims¶

spring.datasource.url=jdbc:postgresql://localhost:5432/demo spring.datasource.username=postgres spring.datasource.password=password

HIBERNATE ENGINE CONFIGURATION¶

Create-drop means create the databse schema when app starts and delete on shutdown¶

spring.jpa.hibernate.ddl-auto=create-drop

Hibernate has clreated dialect classes for database that wraps drivers¶

spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.PostgreSQLDialect

defer Spring's data.sql execution until after JPA/Hibernate has created the schema¶

add below if you use other file name than import.sql¶

spring.jpa.defer-datasource-initialization=true¶

where to find the data file (optional if you name it data.sql in resources)¶

spring.sql.init.data-locations=classpath:/data.sql¶

show queries generated by hibernate in console¶

spring.jpa.show-sql=true

ensure Spring runs SQL initialization even for non-embedded DBs¶

spring.sql.init.mode=always

Format the sql query on console¶

spring.jpa.properties.hibernate.format_sql=true

add logging config to display SQL statements¶

logging.level.org.hibernate.SQL = debug

Enable debug logs:¶

logging.level.com.zaxxer.hikari=DEBUG¶

spring.datasource.hikari.minimum-idle=1

Hikari?s default pool size is 10¶

spring.datasource.hikari.maximum-pool-size=20

SWAGGER¶

springdoc.swagger-ui.path = /demo.html

application.properties — what it really is¶