Introduction:
This post will mainly serve as personal notes where I document my daily learnings throughout my journey into API development with Java.
First of all, I want to make sure I bring over the practices I learned back when I was still doing Node.js development, and keep the mindset of building applications with a strong and reliable infrastructure.
With that in mind, I should think not just like a regular developer, but also with a cloud-oriented mindset — because I believe everything starts with architecture, and a strong foundation is the key to delivering high-quality results.
Preparation:
With all that being said, I didn’t jump in right away — I first took the time to plan things out.
I started by listing my goals and decided to focus mainly on the setup first. I’ve been employed in several companies before, and it’s always a headache trying to run an existing backend project on a new machine as a new hire.
Most of the time, the only documentation available is a README file with just two commands to start the app — only to later find out that it doesn’t work on my machine because of missing prerequisites that weren’t mentioned anywhere. Then I’d end up bothering my new co-workers for help when they’re clearly busy.
With that experience in mind, I want to make this app easy to set up right from the start.
My App goals are:
- Build a basic Spring Boot application with a single “Hello World” endpoint ~ starting simple (CRUD app later on).
- Include necessary dependencies such as a database, and ensure hot-reload is enabled for faster development.
- Make the project easy to set up and run for anyone — not just myself.
- If it runs on my machine, it should run on others without issues.
- Keep the app's folder structure minimal for now
- Make it future-ready for cloud deployment (e.g., AWS) — with configuration files properly structured from the beginning.
My personal goals are:
- Strengthen my OOP knowledge while building this app, since I come from a functional programming background.
- Understand Java core concepts and the Spring Boot folder structure and layering (controllers, models, services, etc.).
- Follow and research tutorials along the way.
- Use AI whenever I have questions or get stuck.
- Compare Spring Boot and Express.js to identify their similarities and differences in REST API development.
- Apply modern tools or dependencies if they can speed up development time.
Now that I have goals in mind, I should make them into reality.
Generating the App:
- Since the goal is to make a springboot app, I learned that https://start.spring.io/ is the go-to for everyone who wants to start out. It generates a new springboot app for you easily.
On spring initializr, you can choose which dependencies you want right from the beginning and input your project name:
It generated a project with folder structure as follows:
canspring/
├── src/
│ ├── main/
│ │ ├── java/
│ │ │ └── com/example/canspring/
│ │ │ └── CanspringApplication.java
│ │ └── resources/
│ │ ├── application.properties
│ │ ├── static/
| | └── templates/
│ └── test/
│ └── java/
│ └── com/example/canspring/
│ └── CanspringApplicationTests.java
├── .mvn/
│ └── wrapper/
│ └── maven-wrapper.properties
├── pom.xml
├── mvnw
├── mvnw.cmd
├── HELP.md
├── .gitignore
└── .gitattributes
To actually run this generated app locally, and get a hello world output, people would normally need to install the Java SDK — but I decided not to do that. My goal is to ensure this app runs consistently on any computer, and if someone else has a different version of Java installed, a lot of things could easily fail.
So to proceed,
Containerizing the App: (Analogy)
- Docker is an amazing tool that allows us to package our app and make it portable. This is the solution I chose so the app can be easily set up on any machine — without needing local installations of Java or PostgreSQL. Containerized apps like this can also be smoothly deployed to AWS or any cloud server.
So basically, if I put the Spring Boot app and the database (I chose PostgreSQL) inside containers instead of installing them manually on my computer. Each container acts like a mini-computer that already has everything it needs — correct Java version, correct database, correct settings.
So the goal is if I run the project, Docker starts both and connects them:
App container → runs Spring Boot
Database container → runs PostgreSQL
No need to install Java or PostgreSQL on my local machine — everything is self-contained. But of course, I needed to download and install Docker Desktop: https://docs.docker.com/desktop/setup/install/windows-install/ and this should be the only thing I need to install moving forward. Nothin more...
Diagram:
┌───────────────────────────────┐
│ Docker Engine │
│ (runs on your computer) │
└───────────────────────────────┘
│
┌────────────┼───────────────────────────┐
│ │ │
┌──────────┐ ┌──────────┐ (optional more containers later)
│ App │ │ DB │
│ Container│ │ Container│
│ (Spring │ │ (Postgre │
│ Boot) │ │ SQL) │
└──────────┘ └──────────┘
│ │
└─ connects ─┘ via *internal* Docker network
< NO need to install Java or Postgres locally >
< portable, same setup runs on any computer or cloud >
- I followed this tutorial in installing Docker: https://www.youtube.com/watch?v=ZyBBv1JmnWQ
- Note that Docker Desktop needs either Hyper-V (can be enabled in your computer's bios settings) or WSL2 (if running on a windows machine like me)
Containerizing the App: (Actual)
- Now that I have docker locally installed, I can begin packaging my app. To do this, I need to add 2 files in my generated spring boot project (Dockerfile and docker-compose.yml) so Docker can run both the Spring Boot app and PostgreSQL.
canspring/
├── src/
│ ├── main/
│ │ ├── java/
│ │ │ └── com/example/canspring/
│ │ │ └── CanspringApplication.java
│ │ └── resources/
│ │ ├── application.properties <- defines connection to database
│ │ ├── static/
| | └── templates/
│ └── test/
│ └── java/
│ └── com/example/canspring/
│ └── CanspringApplicationTests.java
├── .mvn/
│ └── wrapper/
│ └── maven-wrapper.properties
├── pom.xml
├── mvnw
├── mvnw.cmd
├── HELP.md
├── .gitignore
├── .gitattributes
├── Dockerfile ← tells Docker how to build and run this Spring Boot app
└── docker-compose.yml ← starts multiple containers together (app + database)
Below is the content of my DockerFile:
FROM eclipse-temurin:17-jdk
# Set work directory
WORKDIR /app
# Copy pom.xml and download dependencies (cached)
COPY pom.xml .
COPY mvnw ./
COPY .mvn .mvn/
RUN ./mvnw dependency:go-offline
# Copy the entire source code
COPY src ./src
# Expose port 8080
EXPOSE 8080
# Run Spring Boot in dev mode (restart + live reload)
ENTRYPOINT ["./mvnw", "spring-boot:run"]
And... below is the content of my docker-compose.yml file:
version: "3.9"
services:
app:
build:
context: .
dockerfile: Dockerfile
container_name: canspring
ports:
- "8080:8080"
develop:
watch:
# Sync source files directly into the container (instant updates)
- action: sync+restart
path: ./src
target: /app/src
# If POM changes, rebuild the whole image
- action: rebuild
path: pom.xml
environment:
SPRING_PROFILES_ACTIVE: docker
depends_on:
- db
db:
image: postgres:15
container_name: postgresdb
restart: always
environment:
POSTGRES_DB: mydb
POSTGRES_USER: postgres
POSTGRES_PASSWORD: postgres
ports:
- "5432:5432"
volumes:
- pgdata:/var/lib/postgresql/data
volumes:
pgdata:
Also need to add some database config to applicaton.properties:
spring.application.name=canspring
spring.datasource.url=jdbc:postgresql://db:5432/mydb
spring.datasource.username=postgres
spring.datasource.password=postgres
spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true
# Enable DevTools in Docker
spring.devtools.restart.enabled=true
spring.devtools.livereload.enabled=true
spring.devtools.remote.secret=mysecret
spring.thymeleaf.cache=false
These docker files should work as config files to package our app and run it. The command I needed to input is:
docker-compose up --build
- here is the full terminal log:
PS C:\Users\Jack\Downloads\canspring> docker-compose up --build
time="2025-10-22T11:08:32+08:00" level=warning msg="C:\\Users\\Jack\\Downloads\\canspring\\docker-compose.yml: the attribute `version` is obsolete, it will be ignored, please remove it to avoid potential confusion"
[+] Building 2.5s (15/15) FINISHED
=> [internal] load local bake definitions 0.0s
=> => reading from stdin 520B 0.0s
=> [internal] load build definition from Dockerfile 0.0s
=> => transferring dockerfile: 423B 0.0s
=> [internal] load metadata for docker.io/library/eclipse-temurin:17-jdk 1.8s
=> [auth] library/eclipse-temurin:pull token for registry-1.docker.io 0.0s
=> [internal] load .dockerignore 0.0s
=> => transferring context: 2B 0.0s
=> [1/7] FROM docker.io/library/eclipse-temurin:17-jdk@sha256:54a16ef91e00c11ac9b05029faa5efd02c37296844204a 0.0s
=> => resolve docker.io/library/eclipse-temurin:17-jdk@sha256:54a16ef91e00c11ac9b05029faa5efd02c37296844204a 0.0s
=> [internal] load build context 0.0s
=> => transferring context: 1.35kB 0.0s
=> CACHED [2/7] WORKDIR /app 0.0s
=> CACHED [3/7] COPY pom.xml . 0.0s
=> CACHED [4/7] COPY mvnw ./ 0.0s
=> CACHED [5/7] COPY .mvn .mvn/ 0.0s
=> CACHED [6/7] RUN ./mvnw dependency:go-offline 0.0s
=> [7/7] COPY src ./src 0.1s
=> exporting to image 0.2s
=> => exporting layers 0.1s
=> => exporting manifest sha256:44333803fb316c5a1afd958c9859e16b005c9fc1cb35140bca23891ff83f7c55 0.0s
=> => exporting config sha256:2605cb31244d69b6f9a4fc5d689dcb5464acb90e867fda7e03cbb2de8a213659 0.0s
=> => exporting attestation manifest sha256:94c4a4de744afd58150fd9b401c847335bc217158f440010ad60f5ae686e37c6 0.0s
=> => exporting manifest list sha256:5a37253c53212b184db420b14b84f39552cb709994b2fa5af7e9697f0bbabcea 0.0s
=> => naming to docker.io/library/canspring-app:latest 0.0s
=> => unpacking to docker.io/library/canspring-app:latest 0.0s
=> resolving provenance for metadata file 0.0s
[+] Running 4/4
✔ canspring-app Built 0.0s
✔ Network canspring_default Created 0.1s
✔ Container postgresdb Created 0.1s
✔ Container canspring Created 0.1s
Attaching to canspring, postgresdb
postgresdb |
postgresdb | PostgreSQL Database directory appears to contain a database; Skipping initialization
postgresdb |
postgresdb | 2025-10-22 03:08:36.639 UTC [1] LOG: starting PostgreSQL 15.14 (Debian 15.14-1.pgdg13+1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 14.2.0-19) 14.2.0, 64-bit
postgresdb | 2025-10-22 03:08:36.641 UTC [1] LOG: listening on IPv4 address "0.0.0.0", port 5432
postgresdb | 2025-10-22 03:08:36.641 UTC [1] LOG: listening on IPv6 address "::", port 5432
postgresdb | 2025-10-22 03:08:36.646 UTC [1] LOG: listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
postgresdb | 2025-10-22 03:08:36.660 UTC [29] LOG: database system was shut down at 2025-10-22 03:05:17 UTC
postgresdb | 2025-10-22 03:08:36.687 UTC [1] LOG: database system is ready to accept connections
canspring | [INFO] Scanning for projects...
canspring | [INFO]
canspring | [INFO] -----------------------< com.example:canspring >------------------------
canspring | [INFO] Building canspring 0.0.1-SNAPSHOT
canspring | [INFO] from pom.xml
canspring | [INFO] --------------------------------[ jar ]---------------------------------
canspring | [INFO]
canspring | [INFO] >>> spring-boot:3.5.6:run (default-cli) > test-compile @ canspring >>>
canspring | Downloading from central: https://repo.maven.apache.org/maven2/io/micrometer/micrometer-observation/1.15.4/micrometer-observation-1.15.4.pom
Downloaded from central: https://repo.maven.apache.org/maven2/io/micrometer/micrometer-observation/1.15.4/micrometer-observation-1.15.4.pom (3.8 kB at 7.6 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/io/micrometer/micrometer-commons/1.15.4/micrometer-commons-1.15.4.pom
Downloaded from central: https://repo.maven.apache.org/maven2/io/micrometer/micrometer-commons/1.15.4/micrometer-commons-1.15.4.pom (3.4 kB at 45 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/org/jboss/logging/jboss-logging/3.6.1.Final/jboss-logging-3.6.1.Final.pom
Downloaded from central: https://repo.maven.apache.org/maven2/org/jboss/logging/jboss-logging/3.6.1.Final/jboss-logging-3.6.1.Final.pom (18 kB at 241 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/org/jboss/logging/logging-parent/1.0.3.Final/logging-parent-1.0.3.Final.pom
Downloaded from central: https://repo.maven.apache.org/maven2/org/jboss/logging/logging-parent/1.0.3.Final/logging-parent-1.0.3.Final.pom (5.7 kB at 78 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/org/jboss/jboss-parent/42/jboss-parent-42.pom
Downloaded from central: https://repo.maven.apache.org/maven2/org/jboss/jboss-parent/42/jboss-parent-42.pom (76 kB at 812 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/com/fasterxml/classmate/1.7.0/classmate-1.7.0.pom
Downloaded from central: https://repo.maven.apache.org/maven2/com/fasterxml/classmate/1.7.0/classmate-1.7.0.pom (7.0 kB at 98 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/com/fasterxml/oss-parent/56/oss-parent-56.pom
Downloaded from central: https://repo.maven.apache.org/maven2/com/fasterxml/oss-parent/56/oss-parent-56.pom (24 kB at 327 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/net/bytebuddy/byte-buddy/1.17.7/byte-buddy-1.17.7.pom
Downloaded from central: https://repo.maven.apache.org/maven2/net/bytebuddy/byte-buddy/1.17.7/byte-buddy-1.17.7.pom (19 kB at 252 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/net/bytebuddy/byte-buddy-parent/1.17.7/byte-buddy-parent-1.17.7.pom
Downloaded from central: https://repo.maven.apache.org/maven2/net/bytebuddy/byte-buddy-parent/1.17.7/byte-buddy-parent-1.17.7.pom (65 kB at 745 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/jakarta/activation/jakarta.activation-api/2.1.4/jakarta.activation-api-2.1.4.pom
Downloaded from central: https://repo.maven.apache.org/maven2/jakarta/activation/jakarta.activation-api/2.1.4/jakarta.activation-api-2.1.4.pom (19 kB at 247 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/org/glassfish/jaxb/jaxb-runtime/4.0.5/jaxb-runtime-4.0.5.pom
Downloaded from central: https://repo.maven.apache.org/maven2/org/glassfish/jaxb/jaxb-runtime/4.0.5/jaxb-runtime-4.0.5.pom (11 kB at 134 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/com/sun/xml/bind/mvn/jaxb-runtime-parent/4.0.5/jaxb-runtime-parent-4.0.5.pom
Downloaded from central: https://repo.maven.apache.org/maven2/com/sun/xml/bind/mvn/jaxb-runtime-parent/4.0.5/jaxb-runtime-parent-4.0.5.pom (1.2 kB at 15 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/com/sun/xml/bind/mvn/jaxb-parent/4.0.5/jaxb-parent-4.0.5.pom
Downloaded from central: https://repo.maven.apache.org/maven2/com/sun/xml/bind/mvn/jaxb-parent/4.0.5/jaxb-parent-4.0.5.pom (35 kB at 467 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/com/sun/xml/bind/jaxb-bom-ext/4.0.5/jaxb-bom-ext-4.0.5.pom
Downloaded from central: https://repo.maven.apache.org/maven2/com/sun/xml/bind/jaxb-bom-ext/4.0.5/jaxb-bom-ext-4.0.5.pom (3.5 kB at 46 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/org/glassfish/jaxb/jaxb-core/4.0.5/jaxb-core-4.0.5.pom
Downloaded from central: https://repo.maven.apache.org/maven2/org/glassfish/jaxb/jaxb-core/4.0.5/jaxb-core-4.0.5.pom (3.7 kB at 50 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/org/eclipse/angus/angus-activation/2.0.2/angus-activation-2.0.2.pom
Downloaded from central: https://repo.maven.apache.org/maven2/org/eclipse/angus/angus-activation/2.0.2/angus-activation-2.0.2.pom (4.0 kB at 47 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/org/eclipse/angus/angus-activation-project/2.0.2/angus-activation-project-2.0.2.pom
Downloaded from central: https://repo.maven.apache.org/maven2/org/eclipse/angus/angus-activation-project/2.0.2/angus-activation-project-2.0.2.pom (21 kB at 282 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/org/glassfish/jaxb/txw2/4.0.5/txw2-4.0.5.pom
Downloaded from central: https://repo.maven.apache.org/maven2/org/glassfish/jaxb/txw2/4.0.5/txw2-4.0.5.pom (1.8 kB at 24 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/com/sun/xml/bind/mvn/jaxb-txw-parent/4.0.5/jaxb-txw-parent-4.0.5.pom
Downloaded from central: https://repo.maven.apache.org/maven2/com/sun/xml/bind/mvn/jaxb-txw-parent/4.0.5/jaxb-txw-parent-4.0.5.pom (1.2 kB at 17 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/com/sun/istack/istack-commons-runtime/4.1.2/istack-commons-runtime-4.1.2.pom
Downloaded from central: https://repo.maven.apache.org/maven2/com/sun/istack/istack-commons-runtime/4.1.2/istack-commons-runtime-4.1.2.pom (1.6 kB at 21 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/com/sun/istack/istack-commons/4.1.2/istack-commons-4.1.2.pom
Downloaded from central: https://repo.maven.apache.org/maven2/com/sun/istack/istack-commons/4.1.2/istack-commons-4.1.2.pom (26 kB at 333 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/org/aspectj/aspectjweaver/1.9.24/aspectjweaver-1.9.24.pom
Downloaded from central: https://repo.maven.apache.org/maven2/org/aspectj/aspectjweaver/1.9.24/aspectjweaver-1.9.24.pom (2.2 kB at 26 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/net/bytebuddy/byte-buddy-agent/1.17.7/byte-buddy-agent-1.17.7.pom
Downloaded from central: https://repo.maven.apache.org/maven2/net/bytebuddy/byte-buddy-agent/1.17.7/byte-buddy-agent-1.17.7.pom (14 kB at 184 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/org/jboss/logging/jboss-logging/3.6.1.Final/jboss-logging-3.6.1.Final.jar
Downloaded from central: https://repo.maven.apache.org/maven2/org/jboss/logging/jboss-logging/3.6.1.Final/jboss-logging-3.6.1.Final.jar (62 kB at 703 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/com/fasterxml/classmate/1.7.0/classmate-1.7.0.jar
canspring | Downloading from central: https://repo.maven.apache.org/maven2/net/bytebuddy/byte-buddy/1.17.7/byte-buddy-1.17.7.jar
canspring | Downloading from central: https://repo.maven.apache.org/maven2/org/glassfish/jaxb/jaxb-runtime/4.0.5/jaxb-runtime-4.0.5.jar
canspring | Downloading from central: https://repo.maven.apache.org/maven2/org/glassfish/jaxb/jaxb-core/4.0.5/jaxb-core-4.0.5.jar
canspring | Downloading from central: https://repo.maven.apache.org/maven2/org/eclipse/angus/angus-activation/2.0.2/angus-activation-2.0.2.jar
Downloaded from central: https://repo.maven.apache.org/maven2/com/fasterxml/classmate/1.7.0/classmate-1.7.0.jar (69 kB at 644 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/org/glassfish/jaxb/txw2/4.0.5/txw2-4.0.5.jar
Downloaded from central: https://repo.maven.apache.org/maven2/org/glassfish/jaxb/txw2/4.0.5/txw2-4.0.5.jar (73 kB at 421 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/com/sun/istack/istack-commons-runtime/4.1.2/istack-commons-runtime-4.1.2.jar
Downloaded from central: https://repo.maven.apache.org/maven2/org/eclipse/angus/angus-activation/2.0.2/angus-activation-2.0.2.jar (27 kB at 131 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/org/aspectj/aspectjweaver/1.9.24/aspectjweaver-1.9.24.jar
Downloaded from central: https://repo.maven.apache.org/maven2/com/sun/istack/istack-commons-runtime/4.1.2/istack-commons-runtime-4.1.2.jar (26 kB at 107 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/io/micrometer/micrometer-observation/1.15.4/micrometer-observation-1.15.4.jar
Downloaded from central: https://repo.maven.apache.org/maven2/io/micrometer/micrometer-observation/1.15.4/micrometer-observation-1.15.4.jar (75 kB at 226 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/io/micrometer/micrometer-commons/1.15.4/micrometer-commons-1.15.4.jar
Downloaded from central: https://repo.maven.apache.org/maven2/org/glassfish/jaxb/jaxb-runtime/4.0.5/jaxb-runtime-4.0.5.jar (920 kB at 2.3 MB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/jakarta/activation/jakarta.activation-api/2.1.4/jakarta.activation-api-2.1.4.jar
Downloaded from central: https://repo.maven.apache.org/maven2/io/micrometer/micrometer-commons/1.15.4/micrometer-commons-1.15.4.jar (49 kB at 113 kB/s)
canspring | Downloading from central: https://repo.maven.apache.org/maven2/net/bytebuddy/byte-buddy-agent/1.17.7/byte-buddy-agent-1.17.7.jar
Downloaded from central: https://repo.maven.apache.org/maven2/jakarta/activation/jakarta.activation-api/2.1.4/jakarta.activation-api-2.1.4.jar (67 kB at 131 kB/s)
Downloaded from central: https://repo.maven.apache.org/maven2/net/bytebuddy/byte-buddy-agent/1.17.7/byte-buddy-agent-1.17.7.jar (366 kB at 616 kB/s)
Downloaded from central: https://repo.maven.apache.org/maven2/org/glassfish/jaxb/jaxb-core/4.0.5/jaxb-core-4.0.5.jar (139 kB at 219 kB/s)
Downloaded from central: https://repo.maven.apache.org/maven2/org/aspectj/aspectjweaver/1.9.24/aspectjweaver-1.9.24.jar (2.2 MB at 3.3 MB/s)
Downloaded from central: https://repo.maven.apache.org/maven2/net/bytebuddy/byte-buddy/1.17.7/byte-buddy-1.17.7.jar (9.0 MB at 11 MB/s)
canspring | [INFO]
canspring | [INFO] --- resources:3.3.1:resources (default-resources) @ canspring ---
canspring | [INFO] Copying 1 resource from src/main/resources to target/classes
canspring | [INFO] Copying 0 resource from src/main/resources to target/classes
canspring | [INFO]
canspring | [INFO] --- compiler:3.14.0:compile (default-compile) @ canspring ---
canspring | [INFO] Recompiling the module because of changed source code.
canspring | [INFO] Compiling 1 source file with javac [debug parameters release 17] to target/classes
canspring | [INFO]
canspring | [INFO] --- resources:3.3.1:testResources (default-testResources) @ canspring ---
canspring | [INFO] skip non existing resourceDirectory /app/src/test/resources
canspring | [INFO]
canspring | [INFO] --- compiler:3.14.0:testCompile (default-testCompile) @ canspring ---
canspring | [INFO] Recompiling the module because of changed dependency.
canspring | [INFO] Compiling 1 source file with javac [debug parameters release 17] to target/test-classes
canspring | [INFO]
canspring | [INFO] <<< spring-boot:3.5.6:run (default-cli) < test-compile @ canspring <<<
canspring | [INFO]
canspring | [INFO]
canspring | [INFO] --- spring-boot:3.5.6:run (default-cli) @ canspring ---
canspring | [INFO] Attaching agents: []
canspring |
canspring | . ____ _ __ _ _
canspring | /\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
canspring | ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
canspring | \\/ ___)| |_)| | | | | || (_| | ) ) ) )
canspring | ' |____| .__|_| |_|_| |_\__, | / / / /
canspring | =========|_|==============|___/=/_/_/_/
canspring |
canspring | :: Spring Boot :: (v3.5.6)
canspring |
canspring | 2025-10-22T03:08:44.466Z INFO 187 --- [canspring] [ restartedMain] c.e.canspring.CanspringApplication : Starting CanspringApplication using Java 17.0.16 with PID 187 (/app/target/classes started by root in /app)
canspring | 2025-10-22T03:08:44.468Z INFO 187 --- [canspring] [ restartedMain] c.e.canspring.CanspringApplication : The following 1 profile is active: "docker"
canspring | 2025-10-22T03:08:44.513Z INFO 187 --- [canspring] [ restartedMain] .e.DevToolsPropertyDefaultsPostProcessor : Devtools property defaults active! Set 'spring.devtools.add-properties' to 'false' to disable
canspring | 2025-10-22T03:08:44.514Z INFO 187 --- [canspring] [ restartedMain] .e.DevToolsPropertyDefaultsPostProcessor : For additional web related logging consider setting the 'logging.level.web' property to 'DEBUG'
canspring | 2025-10-22T03:08:44.979Z INFO 187 --- [canspring] [ restartedMain] .s.d.r.c.RepositoryConfigurationDelegate : Bootstrapping Spring Data JPA repositories in DEFAULT mode.
canspring | 2025-10-22T03:08:44.997Z INFO 187 --- [canspring] [ restartedMain] .s.d.r.c.RepositoryConfigurationDelegate : Finished Spring Data repository scanning in 9 ms. Found 0 JPA repository interfaces.
canspring | 2025-10-22T03:08:45.346Z INFO 187 --- [canspring] [ restartedMain] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port 8080 (http)
canspring | 2025-10-22T03:08:45.357Z INFO 187 --- [canspring] [ restartedMain] o.apache.catalina.core.StandardService : Starting service [Tomcat]
canspring | 2025-10-22T03:08:45.357Z INFO 187 --- [canspring] [ restartedMain] o.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/10.1.46]
canspring | 2025-10-22T03:08:45.390Z INFO 187 --- [canspring] [ restartedMain] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
canspring | 2025-10-22T03:08:45.391Z INFO 187 --- [canspring] [ restartedMain] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 876 ms
canspring | 2025-10-22T03:08:45.409Z WARN 187 --- [canspring] [ restartedMain] .s.b.d.a.RemoteDevToolsAutoConfiguration : Listening for remote restart updates on /.~~spring-boot!~/restart
canspring | 2025-10-22T03:08:45.566Z INFO 187 --- [canspring] [ restartedMain] o.hibernate.jpa.internal.util.LogHelper : HHH000204: Processing PersistenceUnitInfo [name: default]
canspring | 2025-10-22T03:08:45.638Z INFO 187 --- [canspring] [ restartedMain] org.hibernate.Version : HHH000412: Hibernate ORM core version 6.6.29.Final
canspring | 2025-10-22T03:08:45.676Z INFO 187 --- [canspring] [ restartedMain] o.h.c.internal.RegionFactoryInitiator : HHH000026: Second-level cache disabled
canspring | 2025-10-22T03:08:45.905Z INFO 187 --- [canspring] [ restartedMain] o.s.o.j.p.SpringPersistenceUnitInfo : No LoadTimeWeaver setup: ignoring JPA class transformer
canspring | 2025-10-22T03:08:45.934Z INFO 187 --- [canspring] [ restartedMain] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Starting...
canspring | 2025-10-22T03:08:46.101Z INFO 187 --- [canspring] [ restartedMain] com.zaxxer.hikari.pool.HikariPool : HikariPool-1 - Added connection org.postgresql.jdbc.PgConnection@1280d447
canspring | 2025-10-22T03:08:46.103Z INFO 187 --- [canspring] [ restartedMain] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Start completed.
canspring | 2025-10-22T03:08:46.194Z INFO 187 --- [canspring] [ restartedMain] org.hibernate.orm.connections.pooling : HHH10001005: Database info:
canspring | Database JDBC URL [Connecting through datasource 'HikariDataSource (HikariPool-1)']
canspring | Database driver: undefined/unknown
canspring | Database version: 15.14
canspring | Autocommit mode: undefined/unknown
canspring | Isolation level: undefined/unknown
canspring | Minimum pool size: undefined/unknown
canspring | Maximum pool size: undefined/unknown
canspring | 2025-10-22T03:08:46.473Z INFO 187 --- [canspring] [ restartedMain] o.h.e.t.j.p.i.JtaPlatformInitiator : HHH000489: No JTA platform available (set 'hibernate.transaction.jta.platform' to enable JTA platform integration)
canspring | 2025-10-22T03:08:46.477Z INFO 187 --- [canspring] [ restartedMain] j.LocalContainerEntityManagerFactoryBean : Initialized JPA EntityManagerFactory for persistence unit 'default'
canspring | 2025-10-22T03:08:46.513Z WARN 187 --- [canspring] [ restartedMain] JpaBaseConfiguration$JpaWebConfiguration : spring.jpa.open-in-view is enabled by default. Therefore, database queries may be performed during view rendering. Explicitly configure spring.jpa.open-in-view to disable this warning
canspring | 2025-10-22T03:08:46.849Z INFO 187 --- [canspring] [ restartedMain] o.s.b.d.a.OptionalLiveReloadServer : LiveReload server is running on port 35729
canspring | 2025-10-22T03:08:46.878Z INFO 187 --- [canspring] [ restartedMain] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port 8080 (http) with context path '/'
canspring | 2025-10-22T03:08:46.887Z INFO 187 --- [canspring] [ restartedMain] c.e.canspring.CanspringApplication : Started CanspringApplication in 2.768 seconds (process running for 3.116)
I determined that:
- This shows that application has been built
- springboot app has also connected to a postgres database
- and started on localhost:8080
Next thing is to just create a get endpoint that would return a 'Hello World' text:
I added a controller file in \canspring\src\main\java\com\example\canspring\controller\HelloController.java with the following code below
package com.example.canspring.controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class HelloController {
// A simple REST endpoint
@GetMapping("/hello")
public String hello() {
return "Hello World!";
}
}
Then tested this on my browser by typing localhost:8080/hello on the URL and it did not work :( it showed me a white label error which means that the endpoint does not exist...
So far I understood that every time there are new files created inside my project, like the controller I just created, I always needed to rebuild the docker image so that those files can be copied by docker...
when I rebuilt my spring boot app using docker-compose up --build, the app started... Then I went to localhost:8080/hello again and everything worked!
Then I updated my controller to output a new text: Hello World! with springboot and docker!
I see logs that it detected that there was a change in the controller I updated:
⦿ Syncing service "app" after 2 changes were detected
canspring | 2025-10-22T04:20:03.491Z INFO 180 --- [canspring] [ionShutdownHook] o.s.b.w.e.tomcat.GracefulShutdown : Commencing graceful shutdown. Waiting for active requests to complete
canspring | 2025-10-22T04:20:03.497Z INFO 180 --- [canspring] [tomcat-shutdown] o.s.b.w.e.tomcat.GracefulShutdown : Graceful shutdown complete
canspring | 2025-10-22T04:20:03.503Z INFO 180 --- [canspring] [ionShutdownHook] j.LocalContainerEntityManagerFactoryBean : Closing JPA EntityManagerFactory for persistence unit 'default'
canspring | 2025-10-22T04:20:03.509Z INFO 180 --- [canspring] [ionShutdownHook] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Shutdown initiated...
canspring | 2025-10-22T04:20:03.517Z INFO 180 --- [canspring] [ionShutdownHook] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Shutdown completed.
⦿ service(s) ["app"] restarted
canspring exited with code 143 (restarting)
canspring | [INFO] Scanning for projects...
canspring | [INFO]
canspring | [INFO] -----------------------< com.example:canspring >------------------------
canspring | [INFO] Building canspring 0.0.1-SNAPSHOT
canspring | [INFO] from pom.xml
canspring | [INFO] --------------------------------[ jar ]---------------------------------
canspring | [INFO]
canspring | [INFO] >>> spring-boot:3.5.6:run (default-cli) > test-compile @ canspring >>>
canspring | [INFO]
canspring | [INFO] --- resources:3.3.1:resources (default-resources) @ canspring ---
canspring | [INFO] Copying 1 resource from src/main/resources to target/classes
canspring | [INFO] Copying 0 resource from src/main/resources to target/classes
canspring | [INFO]
canspring | [INFO] --- compiler:3.14.0:compile (default-compile) @ canspring ---
canspring | [INFO] Recompiling the module because of changed source code.
canspring | [INFO] Compiling 2 source files with javac [debug parameters release 17] to target/classes
canspring | [INFO]
canspring | [INFO] --- resources:3.3.1:testResources (default-testResources) @ canspring ---
canspring | [INFO] skip non existing resourceDirectory /app/src/test/resources
canspring | [INFO]
canspring | [INFO] --- compiler:3.14.0:testCompile (default-testCompile) @ canspring ---
canspring | [INFO] Recompiling the module because of changed dependency.
canspring | [INFO] Compiling 1 source file with javac [debug parameters release 17] to target/test-classes
canspring | [INFO]
canspring | [INFO] <<< spring-boot:3.5.6:run (default-cli) < test-compile @ canspring <<<
canspring | [INFO]
canspring | [INFO]
canspring | [INFO] --- spring-boot:3.5.6:run (default-cli) @ canspring ---
canspring | [INFO] Attaching agents: []
canspring |
canspring | . ____ _ __ _ _
canspring | /\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
canspring | ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
canspring | \\/ ___)| |_)| | | | | || (_| | ) ) ) )
canspring | ' |____| .__|_| |_|_| |_\__, | / / / /
canspring | =========|_|==============|___/=/_/_/_/
canspring |
canspring | :: Spring Boot :: (v3.5.6)
canspring |
canspring | 2025-10-22T04:20:08.785Z INFO 180 --- [canspring] [ restartedMain] c.e.canspring.CanspringApplication : Starting CanspringApplication using Java 17.0.16 with PID 180 (/app/target/classes started by root in /app)
canspring | 2025-10-22T04:20:08.787Z INFO 180 --- [canspring] [ restartedMain] c.e.canspring.CanspringApplication : The following 1 profile is active: "docker"
canspring | 2025-10-22T04:20:08.829Z INFO 180 --- [canspring] [ restartedMain] .e.DevToolsPropertyDefaultsPostProcessor : Devtools property defaults active! Set 'spring.devtools.add-properties' to 'false' to disable
canspring | 2025-10-22T04:20:08.829Z INFO 180 --- [canspring] [ restartedMain] .e.DevToolsPropertyDefaultsPostProcessor : For additional web related logging consider setting the 'logging.level.web' property to 'DEBUG'
canspring | 2025-10-22T04:20:09.276Z INFO 180 --- [canspring] [ restartedMain] .s.d.r.c.RepositoryConfigurationDelegate : Bootstrapping Spring Data JPA repositories in DEFAULT mode.
canspring | 2025-10-22T04:20:09.293Z INFO 180 --- [canspring] [ restartedMain] .s.d.r.c.RepositoryConfigurationDelegate : Finished Spring Data repository scanning in 9 ms. Found 0 JPA repository interfaces.
canspring | 2025-10-22T04:20:09.624Z INFO 180 --- [canspring] [ restartedMain] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port 8080 (http)
canspring | 2025-10-22T04:20:09.635Z INFO 180 --- [canspring] [ restartedMain] o.apache.catalina.core.StandardService : Starting service [Tomcat]
canspring | 2025-10-22T04:20:09.636Z INFO 180 --- [canspring] [ restartedMain] o.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/10.1.46]
canspring | 2025-10-22T04:20:09.667Z INFO 180 --- [canspring] [ restartedMain] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
canspring | 2025-10-22T04:20:09.669Z INFO 180 --- [canspring] [ restartedMain] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 839 ms
canspring | 2025-10-22T04:20:09.685Z WARN 180 --- [canspring] [ restartedMain] .s.b.d.a.RemoteDevToolsAutoConfiguration : Listening for remote restart updates on /.~~spring-boot!~/restart
canspring | 2025-10-22T04:20:09.805Z INFO 180 --- [canspring] [ restartedMain] o.hibernate.jpa.internal.util.LogHelper : HHH000204: Processing PersistenceUnitInfo [name: default]
canspring | 2025-10-22T04:20:09.843Z INFO 180 --- [canspring] [ restartedMain] org.hibernate.Version : HHH000412: Hibernate ORM core version 6.6.29.Final
canspring | 2025-10-22T04:20:09.868Z INFO 180 --- [canspring] [ restartedMain] o.h.c.internal.RegionFactoryInitiator : HHH000026: Second-level cache disabled
canspring | 2025-10-22T04:20:10.045Z INFO 180 --- [canspring] [ restartedMain] o.s.o.j.p.SpringPersistenceUnitInfo : No LoadTimeWeaver setup: ignoring JPA class transformer
canspring | 2025-10-22T04:20:10.064Z INFO 180 --- [canspring] [ restartedMain] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Starting...
canspring | 2025-10-22T04:20:10.176Z INFO 180 --- [canspring] [ restartedMain] com.zaxxer.hikari.pool.HikariPool : HikariPool-1 - Added connection org.postgresql.jdbc.PgConnection@7e47f6d5
canspring | 2025-10-22T04:20:10.177Z INFO 180 --- [canspring] [ restartedMain] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Start completed.
canspring | 2025-10-22T04:20:10.235Z INFO 180 --- [canspring] [ restartedMain] org.hibernate.orm.connections.pooling : HHH10001005: Database info:
canspring | Database JDBC URL [Connecting through datasource 'HikariDataSource (HikariPool-1)']
canspring | Database driver: undefined/unknown
canspring | Database version: 15.14
canspring | Autocommit mode: undefined/unknown
canspring | Isolation level: undefined/unknown
canspring | Minimum pool size: undefined/unknown
canspring | Maximum pool size: undefined/unknown
canspring | 2025-10-22T04:20:10.441Z INFO 180 --- [canspring] [ restartedMain] o.h.e.t.j.p.i.JtaPlatformInitiator : HHH000489: No JTA platform available (set 'hibernate.transaction.jta.platform' to enable JTA platform integration)
canspring | 2025-10-22T04:20:10.444Z INFO 180 --- [canspring] [ restartedMain] j.LocalContainerEntityManagerFactoryBean : Initialized JPA EntityManagerFactory for persistence unit 'default'
canspring | 2025-10-22T04:20:10.478Z WARN 180 --- [canspring] [ restartedMain] JpaBaseConfiguration$JpaWebConfiguration : spring.jpa.open-in-view is enabled by default. Therefore, database queries may be performed during view rendering. Explicitly configure spring.jpa.open-in-view to disable this warning
canspring | 2025-10-22T04:20:10.753Z INFO 180 --- [canspring] [ restartedMain] o.s.b.d.a.OptionalLiveReloadServer : LiveReload server is running on port 35729
canspring | 2025-10-22T04:20:10.776Z INFO 180 --- [canspring] [ restartedMain] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port 8080 (http) with context path '/'
canspring | 2025-10-22T04:20:10.785Z INFO 180 --- [canspring] [ restartedMain] c.e.canspring.CanspringApplication : Started CanspringApplication in 2.324 seconds (process running for 2.629)
Then I refreshed the browser: and saw that the changes reflected!
Conclusion:
In summary for Part 1 of my journey:
- I was able to build a Spring Boot app that is containerized (easy to setup and run) and currently connected to a local database without JAVA or Postgres installations. It also hot-reloads whenever I make changes to its classes (controller for now).
Next steps:
- Hot reload should also detect newly added files in the project. Docker should sync those and reflect the changes — not just content changes, but also new files added to a directory.
- Add new endpoints to build a CRUD app (probably a TODO List app or an Expense Tracker app)
Please input your insights on the comments down below! I would greatly appreciate it! Thank you for learning with me!
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