DEV Community: Mohamed Kramti

Getting Started with Maven

Mohamed Kramti — Fri, 18 Oct 2024 19:43:08 +0000

Read full post at Getting Started with Maven

Overview

If you're a Java developer, you've likely used Maven to build and manage your projects.

In this post, you'll learn the basics of using Maven in your projects.

Understanding Maven's Project Structure

my-maven-project/pom.xml

Defines the Maven project. It includes a unique identifier for the project, properties, dependencies, and necessary modules.

my-maven-project/src/main/java

Contains the source code of the project.

my-maven-project/src/main/resources

Contains resource files (like application.properties).

my-maven-project/src/test

Contains the test code.

my-maven-project/src/it

Contains integration tests.

my-maven-project/target

Contains compiled classes, JAR/WAR files, and other artifacts.

POM File

Key Elements

The pom.xml file holds crucial information about the project. Each project must have a unique identifier, specified by:

groupId (usually your domain name)
artifactId (usually the project name)
version (project version)

Additionally, the pom.xml can include the project's name, description, and packaging type (e.g., JAR/WAR).

Example:



<groupId>com.kramti</groupId>

<artifactId>example</artifactId>

<version>1.0</version>

<name>My Maven Example</name>

<description>This is a Maven pom.xml example</description>

<packaging>war</packaging>

<properties>

<java.version>21</java.version>

</properties>

Dependencies

Dependencies are external libraries your project requires. Instead of manually downloading and importing JAR files, Maven simplifies this by managing dependencies within the pom.xml.

To add a dependency, you need its groupId, artifactId, version (optional), and scope (optional). You can find dependencies on the Maven Repository.

Example of a dependency:


<dependency>

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-starter-data-jpa</artifactId>

<version></version>

</dependency>

For example, if you need a dependency only for testing purposes, use the scope tag:

<dependency>

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-starter-test</artifactId>

<scope>test</scope>

</dependency>

Maven Build Lifecycle

validate: Checks if the project is correct and all necessary information is available.
compile: Compiles the project's source code.
test: Runs unit tests using a suitable testing framework.
package: Packages the compiled code into a distributable format (e.g., JAR or WAR).
install: Installs the package into the local repository for use by other projects.
deploy: Deploys the built package to a remote repository for sharing with other developers.

Maven Plugins

Using Maven Plugins Maven plugins are essential for customizing the build process. You can use plugins for tasks such as compiling code, running tests, and generating reports.

Example of a compiler plugin:

<plugin>

<groupId>org.apache.maven.plugins</groupId>

<artifactId>maven-compiler-plugin</artifactId>

<version>3.8.1</version>

<configuration>

<source>1.8</source>

<target>1.8</target>

</configuration>

</plugin>

Popular plugins include:

maven-compiler-plugin: Compiles Java source code.

maven-surefire-plugin: Runs unit tests.

maven-jar-plugin: Packages the project into a JAR file.

Best Practices for Maven Projects

Keep Dependencies Up-to-Date: Regularly update your dependencies to avoid vulnerabilities.

Avoid Version Conflicts: Use the section in the parent POM to manage dependency versions in multi-module projects.

Minimize Plugin Configuration: Keep plugin configurations minimal and only configure what’s necessary for your project.

Build performance: For large projects, Maven builds can be slow. Use the -T option to enable parallel builds

Conclusion

Maven is an essential tool for Java developers. It simplifies project management by automating builds, handling dependencies and plugins. Understanding its structure, POM file, and core features allows for more efficient and organized workflows.

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Java Performance Optimization Techniques

Docker in nutshell

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Java Performance Optimization Techniques

Mohamed Kramti — Thu, 03 Oct 2024 19:44:03 +0000

Hello 👋
You can find the full post on Java Performance Optimization Techniques

1. Overview

Optimizing your code performance is critical for the success of your profile. Did you know that Akamai's research found that 57% of online consumers abandon a website if a page takes longer than 3 seconds to load? In this post, you will learn how to optimize your Java code and improve your code performance.

2. Virtual Threads

Say no more to OutOfMemoryError: unable to create new native thread Error.

Java virtual threads, introduced in Java 19, can significantly improve the performance of your project.

In the previous releases of Java, there was only 1 type of thread (Classic threads) when a classic thread is created an OS thread is allocated and the number of threads is limited to the OS threads.

Starting from JDK 19, you can create virtual threads which are much lighter than OS threads and you can create and run thousands of virtual threads in an application.

To enable virtual threads in a Spring Boot application add the following code to your application.properties.

spring.threads.virtual.enabled=true

3. Lazy loading

A lot of performance problems arise from fetching data that you don't need.

It's best practice to only load objects when needed.

For instance, you can use FetchLazy in Hibernate but always keep in mind that the appropriate fetch strategy depends on the specific use case you're dealing with.

fetch = FetchType.LAZY

4. Cache

Minimize disk access by caching frequently accessed data. By using proper caching techniques you can reduce latency, avoid network congestion and improve content availability.

The Spring framework provides support for various cache providers including but not limited to Redis, Caffeie, Cache2k etc...

5. Avoid GenerationType.TABLE

When choosing a key generation strategy in JPA, it's important to select the one that best fits the database you're using.
GenerationType.TABLE

Avoid using GenerationType.TABLE for its performance overhead. Each time a primary key is needed a LOCK statement is executed, along with a select and update on the sequence table.
GenerationType.IDENTITY

GenerationType.IDENTITY is best suited for MySQL because MySQL uses auto-increment fields and GenerationType.IDENTITY works well with this.
GenerationType.SEQUENCE

GenerationType.SEQUENCE is typically used with PostgreSQL and Oracle. Both databases support sequences, which are database objects that generate a sequence of unique numbers.

6. Query Plan Cache

Hibernate's Query Plan Cache is a key feature that can improve the performance of your application.

When hibernate executes a JPQL query, the corresponding SQL query needs to be generated. This process involves parsing the query to an Abstract Syntax Tree, translating the tree to an SQL query and finally mapping the result back to Java objects.

Once this process is complete, hibernate caches the process so that it doesn't need to perform these steps again for the same query.

To enable and configure the Query Plan cache use the following code:

hibernate.query.plan_cache_max_size=2048 # Maximum number of query plans in the cache hibernate.query.plan_parameter_metadata_max_size=128 # Max size of query plans with parameter metadata

7. Conclusion

Optimizing Java code performance is essential for delivering fast and responsive applications.

By leveraging modern features like virtual threads, implementing lazy loading, using efficient caching strategies, and optimizing your database operations, you can significantly improve your application's performance.

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Getting Started with Maven

Docker in nutshell

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Docker In Nutshell + Docker Cheat Sheet

Mohamed Kramti — Sun, 29 Sep 2024 10:12:31 +0000

Note from the author

Hello 👋

This is my first post on dev.to

If you like my post, please like it and let’s connect on LinkedIn

Check out my blog at https://kramti.com

Scroll to the end of the post for an amazing Docker Cheat Sheet Docker In Nutshell + Docker Cheat Sheet

Introduction

This article covers everything you need to know to start using Docker.

I will begin by presenting Docker and the issues it solves, then I’ll clarify the most used terms related to Docker, and finally, we will dockerize an application and run our first container.

What Problem Does Docker Solve?

1) Settings up an environment can be complex for some people, especially for a less technical person.

Docker will install all the dependencies your application need; You don’t have to worry about setting up your MySQL, installing Java, node or any other tool.

2) If you don’t want to share the filesystem, database, network interface, port or OS … between applications docker got you covered thanks to its isolation technique.

3) Security - Isolation concerns security too, deploying a vulnerable application or a malicious code can damage the other applications, and that's why it’s better to keep apps isolated.

4) Portability - As long as the Docker versions are compatible your shipped software will work anywhere

Key terms

Docker

Docker is an open-source project that:

Will help you deploy your applications.
Packages your applications into an image that can be used anywhere.
Uses containers to run applications in isolated environments

Images

Images contain:
- Application code
- Dependencies
- Configuration
- Runtime environment

Important: Images are read-only you can’t change the content of an image; if you need to change the content of an image you have to create a new image with the changes.

Containers

A container:
- Is a runnable instance of an image.
- Completely Isolated process (runs undependably from any process on your computer).
- Help to improve the deployment of an application.

Note: We can create multiple containers from the same image.

Install Docker

Install Docker on Windows

Install WSL

WSL stands for Windows Subsystem for Linux.

It’s a feature in Windows 10 version 2004+ and windows 11; it allows Linux programs to run on Windows

To install WSL simply run this command on PowerShell

wsl --install

Alternatively, if you want to install it manually follow this guide

Manual installation steps for older versions of WSL | Microsoft Learn

Install Docker Desktop

The next step is to install the Docker Desktop

You can follow this link to download the Docker Desktop

Install Docker Desktop on Windows | Docker Documentation

The installation is really simple we won’t go into in this tutorial

Install Docker on Ubuntu

Before installing docker on your Linux system you must install some dependencies that Docker needs

sudo apt-get install ca-certificates curl gnupg lsb-release

Add the Docker GPG key

sudo mkdir -p /etc/apt/keyrings

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg

Set up the repository

echo \ "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu \ $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

And lastly, install Docker

sudo apt-get update

sudo apt-get install docker-ce docker-ce-cli containerd.io docker-compose-plugin

Install Docker on other platforms

Docker supports a variety of platforms (Linux platforms, macOS and Windows). For more details check the official documentation Install Docker Engine | Docker Documentation

Check the installation

After installing docker you can run your first container using this command

docker run hello-world

Output

Hello from Docker!

This message shows that your installation appears to be working correctly.

…

If you see this message, then congratulation you have successfully installed Docker.

DockerHub

What is DockerHub?

Docker Hub is a service provided by Docker to download and share docker images.

You can access DockerHub from this link Docker Hub Container Image Library | App Containerization

Download an image from DockerHub

Let’s say you need a Linux OS to deploy your application

1- Go to hub.docker.com and search for the OS you need to install I’ll take Ubuntu as an example

2- You will get a variety of images, select the image you need to install in my case the official Ubuntu image

3- Run the docker pull ubuntu command on your terminal, CMD or PowerShell.

Output

…

Status: Downloaded newer image for ubuntu: latest
docker.io/library/ubuntu:latest

Congratulation now you have downloaded your first image, you may have noticed that the image size is way smaller than the official ubuntu Iso image and that’s another advantage of docker.

Note: By default, docker pull ubuntu will pull the latest version, but you can specify the docker version following the image name example docker pull ubuntu:20.04

Note: Alternatively, if you don’t want to go to hub.docker.com and search for the image using your browser you can search for images using your command line simply type

docker search ubuntu

This command will list all the available images, their descriptions and more …

DockerFile

What is a DockerFile?

A DockerFile is a file that contains a set of instructions for docker to create your own image, for example, it may contain the OS your application will run on, the source code of your application etc…

A DockerFile does not have an extension and it contains a set of instructions

How to create a DockerFile?

We learned previously that a DockerFile is a set of instructions below are the most common instructions used on DockerFiles

FROM is used to define the parent image that the new image will be built.

COPY & ADD is used to copy files to the filesystem of the image.

WORKDIR is used to specify the working directory.

RUN is used to run commands to run inside the container.

CMD is used to specify a command that executes by default when running a Docker container.

For more DockerFile instructions visit Dockerfile reference | Docker Documentation

Example: Dockerizing a Node.js web app

Note: Optional you can install a Docker extension in your editor.

Step 1 - Define the parent container

FROM node:16

Step 2 - Define the working directory which will contain our node application

WORKDIR /usr/src/app

Note: The following instructions will be executed inside /usr/src/app

Step 3 - Copy the node application to our image

COPY . .

Note: The first dot represents the current file on our host machine, and the second dot is the current working directory.

Step 4 - Informing Docker of the port our application is listening to

EXPOSE 4444

Step 5 - Installing the application dependencies

RUN npm install

Step 6 - Lastly define the command to run the application

CMD [ "node", "server.js" ]

That’s all! The DockerFile should look like that

FROM node:16

WORKDIR /usr/src/app

COPY . .

EXPOSE 4444

RUN npm install

CMD [ "node", "server.js" ]

DockerIgnore file

The .dockerIgnore file is similar to the .gitignore you simply include the path to the files or folders you want Docker to ignore while dockerizing your application.

In the previous example, we can create a .dockerignore file to ignore the node_modules folder

Simply create a .dockerignore file and it should contain one line

node_modules

Build the Image

Now that we had set up the DockerFile and the .dockerIgnore file we can build our image

to do so simply run the following command:

docker build -t [ Type your image tag here ]

Example

docker build -t myFirstImage

Start & Stop the Container

To start the image created you can use the Docker Desktop application just go to images ⇒ select the image and click run

or we can use the command line

This command displays all the available images

docker images

and to start the container

docker run -p 8080:4444 --name [Give the container a name] [Image name]

Example:

docker run -p 8080:4444 --name myContainer myFirstImage

Note: -p 8080:4444is used to map the 8080 port to the exposed port 4444.

We will be able to access the exposed port using the 8080 port on the local host.

To see the running container run

docker ps

This command displays the running containers along with their ID, created date, and Ports

To stop the container run

docker stop [Container id or Container name]

Example:

docker stop myContainer

Conclusion

In this article you learned pretty much everything you need to get started with Docker from basic concepts, downloading and installing Docker to creating and managing your Docker images and container.