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Crea una REST API sin usar ningún Framework con Java Servlets, JDBC, PostgreSQL y Jackson

📅 February 01, 2025 • 👤 Carlos Chacin • 📖 2 min read

🏷️ Tags: java jdbc postgres postgresql rest api frameworkless servlets

Crea una REST API sin usar ningún Framework con Java Servlets, JDBC, PostgreSQL y Jackson

En éste video, veremos como implementar una REST API sin usar ningún framework como Quarkus, Micronaut, Helidon o Spring Boot. Usaremos Servlets para exponer la API, JDBC para conectarnos a PostgreSQL y Jackson para la serialización a JSON, Integration Testing con Junit5, AssertJ y TestContainers.

Recursos:

Jetty: https://jetty.org/
HikariCP: https://github.com/brettwooldridge/HikariCP
12 Factor Apps: https://12factor.net/
Código: https://github.com/cchacin/frameworkless-rest-api

Parte 1

Parte 2

 ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─
  Servlet Container                                                                   │
 │-----------------             ┌───────────────┐
  Jetty                         │ Serialization │                                     │
 │                              ├───────────────┤
                                │     JSON      │                                     │
 │        ┌───────────────┐     │    -------    │◀─────┐
          │     REST      │     │    Jackson    │      │                              │
 │        ├───────────────┤     └───────────────┘      │
          │   API Layer   │                            │                              │
 │        │   --------    │◀────────────────┐          │
          │   Servlets    │                 │          │                              │
 │        └───────────────┘                 │          │
                                            │          │                              │
 │                                          │          │
                                            │          │                              │
 │        ┌───────────────┐                 │          │       ┌───────────────┐
          │   Core DTOs   │                 │          │       │     Main      │      │
 │        ├───────────────┤                 │          │       ├───────────────┤
          │ Service Layer │                 │          │       │   App Layer   │      │
 │        │ ------------- │◀────────────────┼──────────┴───────│ ------------- │
          │  Plain Java   │                 │                  │  Plain Java   │      │
 │        └───────────────┘                 │                  └───────────────┘
                                            │                                         │
 │                                          │
                                            │                                         │
 │        ┌───────────────┐                 │
          │    DB DTOs    │                 │                                         │
 │        ├───────────────┤                 │
          │  Data Layer   │                 │                                         │
 │        │---------------│◀────────────────┘
          │JDBC / Postgres│                                                           │
 │        └───────────────┘
                  │                                                                   │
 │                │
                  │                                                                   │
 │                │
  ─ ─ ─ ─ ─ ─ ─ ─ ┼ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘
                  │
                  └────────────────────────┐
                                           │
                                           │
                                           │
                                           │
                                           │
                                           │
                                           ▼
┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─
 DATABASE                                                                            │
│----------
 PostgreSQL                                                                          │
│
                                                                                     │
│
                                                                                     │
│
                                                                                     │
│
                                                                                     │
└ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─

🚀 Auto-Switch iTerm2 Modes, Day & Night! 🌞🌚

📅 May 27, 2024 • 👤 Carlos Chacin • 📖 1 min read

🏷️ Tags: iterm2 macos tips-and-tricks terminal productivity

header

iTerm2 recently introduced a great feature: separate light and dark mode colors. This feature enhances the visual appeal of your terminal and keeps it in sync with your Mac’s mode.

This feature is not just about aesthetics; it’s about comfort. Imagine your terminal always matching your Mac’s light or dark mode, creating a seamless and visually pleasing experience. This enhances the visual appeal and reduces eye strain, making your terminal usage more comfortable.

The Problem

In the image below, you can notice that the iTerm2 does not change by default when we switch between light and dark modes.

Java 17 + AWS Lambda

📅 June 06, 2023 • 👤 Carlos Chacin • 📖 1 min read

🏷️ Tags: aws java java17 lambda aws-lambda

Header

AWS recently announced Java 17 support for Lambdas, In this blog post, we’ll explore how to create a Java 17 AWS Lambda Function without IDE, build tool or any dependency.

Fist let’s create the lambda function code:

public class Function {

  public record Input(int x, int y) {}

  public record Output(long result) {}

  public Output add(Input input) {
    return new Output(input.x + input.y);
  }
}

In this example, we have an add method that takes an Input java record with 2 fields: x and y, and returns an Output java record with the sum of x and y assigned to the result field.

This is the only requirement for a AWS Lambda Function:

An instance method that takes one single parameter and returns something an object or Void.

That’s it. Now we can proceed to compile and package our AWS Lambda Function:

Compile:

$ javac Function.java

Package:

$ zip function.zip *.class

Next, let’s navigate to the AWS Lambda Console.

Click on the Create function button.

Assign a lambda name and select Java 17 as the runtime.

Click on the Upload from button.

Click Upload button.

Choose the function.zip file that we generated.

Click Edit on the Code properties section.

Change the Handler to Function::add and click Save.

Go to the Test tab.

Change the JSON payload to:

{
  "x": 123,
  "y": 333
}

Click the Test button, then expand the Details section to see the result.

That’s it! You have successfully created and tested your Java 17 AWS Lambda function. The output should be:

{
  "result": 456
}

This demonstrates the simplicity and power of using Java 17 with AWS Lambda. With just a few steps, you can leverage the latest Java version to build efficient and scalable serverless applications.

Feel free to explore further and unleash the full potential of Java 17 on AWS Lambda. Happy coding!

🏆 Default 🔗 Maven and ☕ Java settings per project

📅 September 23, 2021 • 👤 Carlos Chacin • 📖 1 min read

🏷️ Tags: java maven settings configuration setup

github-actions

I generally use many different options on maven projects to set up things like memory lower and upper limits, fail at the end, the process in batch, use x number of threads, etc. In addition to this, sometimes I need to pass flags to the JVM like add modules, garbage collector flags, etc., and it is difficult to remember and also error-prone to have something like this:

$ JAVA_OPTS="-Xms512m -Xmx1024m -Djava.awt.headless=true" \
  mvn -B -T 4 -fae -P ci verify

or even worst with the extended version of the flags:

$ JAVA_OPTS="-Xms512m -Xmx1024m -Djava.awt.headless=true" \
mvn --batch-mode --threads 4 -fail-at-end --activate-profiles ci verify

Fortunately for us, since maven 3.3.1, we now can setup this per project, including the flags in these two files relatives to the project directory:

☕🚢 Maven Build in < 20 lines of yaml 🕟

📅 September 22, 2021 • 👤 Carlos Chacin • 📖 1 min read

🏷️ Tags: java maven github actions github-actions build

github-actions

GitHub Actions makes it easy to automate all your software workflows, now with world-class CI/CD. Build, test, and deploy your code right from GitHub. Make code reviews, branch management, and issue triaging work the way you want.

Create the directory

$ mkdir -p .github/workflows

Create the yaml file

$ touch .github/workflows/maven.yml

Copy this content

name: Maven Build
on:
  push:
    branches:
      - main
jobs:
  build:
    name: "Maven Build"
    runs-on: ubuntu-latest
    steps:
      - name: "Checkout Sources"
        uses: actions/checkout@v2
        with:
          fetch-depth: 2
      - name: "Set up JDK"
        uses: actions/setup-java@v2
        with:
          distribution: "temurin"
          java-version: 11
          cache: "maven"
      - name: "Build with Maven"
        run: mvn verify

Commit and push to Github

$ git add .github && \
  git commit -m "maven build action"

Enjoy your builds

Go to the actions tab for your repository over github.com:

https://github.com/${USER}/${PROJECT}/actions/workflows/maven-build.yml

maven-build

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Latest Posts

Crea una REST API sin usar ningún Framework con Java Servlets, JDBC, PostgreSQL y Jackson

Parte 1

Parte 2

The Problem

Create the directory

Create the yaml file

Copy this content

Commit and push to Github

Enjoy your builds

🔥 Popular Posts

🔥 Popular Posts

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