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Relational Data Access with Spring JDBC

Coverage Mutation SpotBugs

A Spring Boot console application that demonstrates JdbcTemplate for database operations with H2.

Based on Spring Guide: Accessing Relational Data using JDBC with Spring.

File Index

04-spring-relational-data-access/
├── pom.xml
├── src/main/java/com/example/relationaldataaccess/
│   ├── RelationalDataAccessApplication.java   # Main entry point with CommandLineRunner
│   └── Customer.java                          # Record for customer data
├── src/main/resources/
│   └── application.properties                 # H2 auto-configured (no config needed)
├── src/test/java/com/example/relationaldataaccess/
│   └── RelationalDataAccessApplicationTests.java  # Spring context test
└── docs/
    ├── DEVELOPER_NOTES.md                     # My developer notes
    ├── images/                                # Screenshots
    ├── setup/
    │   ├── spring-initializr.md               # Project setup from start.spring.io
    │   └── run-instructions.md                # Detailed run steps
    ├── concepts/
    │   ├── jdbc-template.md                   # Explains JdbcTemplate and the main app
    │   └── customer.md                        # Explains the Customer record
    ├── reference/
    │   └── guide.md                           # Original Spring guide
    └── adr/                                   # Architecture Decision Records (empty for now)

How It Works

This is a console application that runs once and exits. It uses CommandLineRunner to execute database operations on startup:

sequenceDiagram
    participant App as Spring Boot
    participant JDBC as JdbcTemplate
    participant H2 as H2 Database

    App->>JDBC: execute(CREATE TABLE)
    JDBC->>H2: DDL
    App->>JDBC: batchUpdate(INSERT)
    JDBC->>H2: Insert 4 customers
    App->>JDBC: query(SELECT WHERE first_name = 'Josh')
    JDBC->>H2: Query
    H2-->>JDBC: 2 rows
    JDBC-->>App: List<Customer>
    App->>App: Log results
Loading

Run

./mvnw spring-boot:run

No external database needed - H2 in-memory database is auto-configured.

Console Output

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/

 :: Spring Boot ::                (v4.0.0)

... INFO ... RelationalDataAccessApplication : Creating tables
... INFO ... HikariDataSource       : HikariPool-1 - Start completed.
... INFO ... RelationalDataAccessApplication : Inserting customer record for John Woo
... INFO ... RelationalDataAccessApplication : Inserting customer record for Jeff Dean
... INFO ... RelationalDataAccessApplication : Inserting customer record for Josh Bloch
... INFO ... RelationalDataAccessApplication : Inserting customer record for Josh Long
... INFO ... RelationalDataAccessApplication : Querying for customer records where first_name = 'Josh':
... INFO ... RelationalDataAccessApplication : Customer[id=3, firstName='Josh', lastName='Bloch']
... INFO ... RelationalDataAccessApplication : Customer[id=4, firstName='Josh', lastName='Long']

Terminal Output

Console output showing JdbcTemplate operations

Key Concepts

  • JdbcTemplate - Spring's helper class for SQL operations, handles connections and errors.
  • CommandLineRunner - Interface that runs code after Spring Boot starts.
  • Java Records - Immutable data class (Customer) for holding database rows.
  • Constructor Injection - How Spring provides the JdbcTemplate dependency.
  • RowMapper Lambda - Converts ResultSet rows into Java objects.
  • Batch Update - Efficiently inserts multiple rows in one database call.
  • H2 Database - In-memory database auto-configured by Spring Boot.

Documentation

File Explains
DEVELOPER_NOTES.md My developer notes (Phase 1 & 2)
setup/spring-initializr.md Project setup from start.spring.io
setup/run-instructions.md Detailed run steps
concepts/jdbc-template.md JdbcTemplate methods and main application
concepts/customer.md Customer record, @Override, String.format
reference/guide.md Original Spring guide

JdbcTemplate Methods Used

Method Purpose
execute(sql) Run DDL (CREATE TABLE, DROP TABLE)
batchUpdate(sql, list) Insert multiple rows efficiently
query(sql, rowMapper, params) Select rows and map to objects

Notes

  • Console only - No web server, no HTTP endpoints
  • In-memory database - Data is lost when the app stops
  • Port - N/A (not a web application)

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