My Java Logs: 2023

Monday, December 25, 2023

How to access Multiple Git Account from Single Computer

You might have more than one account in Github one is your personal & another is your office account.

To use both of them in Single Windows PC you can do the following:

Pre-requisite: TorotiseGit is installed

Open the terminal in Windows & run the below command

git config --global credential.useHttpPath true

Now, if you try to checkout a repo , then it will ask for Github account user name & password.

For password use Personal Access Token

Personal Access Token can be generated from Profile--> Settings-->Developer Settings-->Personal access tokens (classic)

Friday, October 27, 2023

SonarQube Postgres Installation

SonarQube with JDK 17 & Postgres as DB backend

DB:

Install Postgres Server 16.x

Execute the below SQL Script from Postgres DB:

CREATE USER sonar ;

ALTER USER sonar WITH PASSWORD 'sonar';

CREATE DATABASE sonardb WITH ENCODING 'UTF8';

ALTER DATABASE sonardb OWNER TO sonar;

SonarQube:

Add SONAR_JAVA_PATH in Environment variable with value like below <Java_Path>\Java\jdk17.0.8_8\bin\javaw.exe

In sonar.properties

1. Update JDBC url

sonar.jdbc.url=jdbc:postgresql://localhost:5432/sonardb?currentSchema=public

2. Update the below 2 properties too

sonar.jdbc.username=sonar

sonar.jdbc.password=sonar

Once done with above steps;

Navigate to <Sonar Path>\sonarqube-10.2.1.78527\bin\windows-x86-64

From Command prompt type StartSonar.bat to start

Sonar should be accessible:

http://localhost:9000/

Friday, August 18, 2023

AI Links

For Google Bard API call

https://github.com/LarryDpk/Google-Bard

https://www.pkslow.com/docs/en/java-library-google-bard/#the-example

For ChatGPT API call:

https://github.com/LiLittleCat/ChatGPT

https://www.bmc.com/blogs/how-to-access-chatgpt-api-java/

Monday, August 14, 2023

How to Zip the Response for Java based Web app

For Spring 4.x based web applications we can use the following stuff to add compression on response

Add the below dependency in pom.xml

<dependency>
   <groupId>net.sf.ehcache</groupId>
   <artifactId>ehcache-web</artifactId>
   <version>2.0.4</version>
</dependency>

Then in web.xml add the below filter declarion:

<filter>
   <filter-name>GzipFilter</filter-name>
   <filter-class>net.sf.ehcache.constructs.web.filter.GzipFilter</filter-class>
</filter>
<filter-mapping>
   <filter-name>GzipFilter</filter-name>
   <url-pattern>/*</url-pattern>
</filter-mapping>

Monday, July 31, 2023

Creating POJO from JSON using Manifold System

Many a times we need to create POJO from JSON samples. This is a tedious job as we need to create a class & then add the properties.

Is there a better way that Java can automatically generate the class parsing the JSON file.

Yes, Manifold System comes to the rescue. (http://manifold.systems/)

Let's see an example:

Pre-requisite:

1. Java 8

2. Intellij IDE

Steps:

Plugin Install:

Open Intellij IDE

Go to Settings->Plugins -> Marketplace

Find Manifold & install the same.

Dependency Addition in Maven Project

First add the below dependencies in pom.xml

<properties>
  <maven.compiler.source>8</maven.compiler.source>
  <maven.compiler.target>8</maven.compiler.target>  
  <manifold.version>2022.1.29</manifold.version>

</properties>

Dependency:

<dependency>
  <groupId>systems.manifold</groupId>
  <artifactId>manifold-json-rt</artifactId>
  <version>${manifold.version}</version>
</dependency>

Build Config:

<build>
  <plugins>
    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-compiler-plugin</artifactId>
      <version>3.8.0</version>
      <configuration>
        <source>8</source>
        <target>8</target>
        <encoding>UTF-8</encoding>
        <compilerArgs>
          <!-- Configure manifold plugin -->
          <arg>-Xplugin:Manifold</arg>
        </compilerArgs>
        <!-- Add the processor path for the plugin -->
        <annotationProcessorPaths>
          <path>
            <groupId>systems.manifold</groupId>
            <artifactId>manifold-json</artifactId>
            <version>${manifold.version}</version>
          </path>
          <path>
            <groupId>systems.manifold</groupId>
            <artifactId>manifold-strings</artifactId>
            <version>${manifold.version}</version>
          </path>
        </annotationProcessorPaths>
      </configuration>
    </plugin>

    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-surefire-plugin</artifactId>
      <version>2.22.2</version>
    </plugin>
  </plugins>
</build>

If Lombok is already used in the project then use below configuration:

 <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.0</version>
                <configuration>
                    <source>8</source>
                    <target>8</target>
                    <encoding>UTF-8</encoding>
                    <compilerArgs>
                        <!-- Configure manifold plugin -->
                        <arg>-Xplugin:Manifold</arg>
                    </compilerArgs>
                    <!-- Add the processor path for the plugin -->
                    <annotationProcessorPaths>

                        <processorPath>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                            <version>1.18.24</version>
                        </processorPath>
                        <processorPath>
                            <groupId>systems.manifold</groupId>
                            <artifactId>manifold-json</artifactId>
                            <version>${manifold.version}</version>
                        </processorPath>
                        <processorPath>
                            <groupId>systems.manifold</groupId>
                            <artifactId>manifold-strings</artifactId>
                            <version>${manifold.version}</version>
                        </processorPath>


                    </annotationProcessorPaths>
                </configuration>
            </plugin>

Code:

Create a sample JSON file in src/main/resources folder.

The file should be created with package structure.

The file name should follow the class name.

E.g.

Create a folder named restapi in src/main/resources/

Create a file named User.json with below content:

{
  "firstName": "Sourav",
  "lastName": "Dalal"
}

A new class User.class will be created dynamically.

The class file will be created under package restapi. You can create any package structure of your choice

You can access the class like below

User testUser = User.create();

testUser.setFirstName("X");
testUser.setLastName("Y");
System.out.println(testUser.write().toJson()
Happy Coding !! :)
Further Reading:
http://manifold.systems/articles/articles.html
https://debugagent.com/revolutionize-json-parsing-in-java-with-manifold

Monday, June 26, 2023

How to use RxJava to process multiple threads in parallel & in sequence

Hi,

In this blog I will discuss 2 scenarios where RxJava threading can be helpful:

1. Run Multiple threads in parallel & wait for all of them to complete

2. Run threads sequentially (one after another)

First, add the below dependency in Maven

<dependency>
    <groupId>io.reactivex.rxjava2</groupId>
    <artifactId>rxjava</artifactId>
    <version>2.2.21</version>
</dependency>

Below are the 2 Completable threads created

import io.reactivex.Completable;
import io.reactivex.schedulers.Schedulers;

Completable cp1= Completable.fromAction(()->{
     //business logic
}).subscribeOn(Schedulers.io());

Completable cp2= Completable.fromAction(()->{
   //business logic
}).subscribeOn(Schedulers.io());
Now for scenario 1
cp1.mergeWith(cp2).blockingAwait(); // cp1 & cp2 will run concurrently & wait for complete for both tasks

For scenario 2
cp1.andThen(cp2).subscribe(); //cp2 will run after cp1

Thursday, June 8, 2023

How to view Wifi Password in Network

Many times you may need to check the password set-up in the Wifi Network. You can use the following steps:

Open Windows command prompt

type in below command replacing the wifi network name

netsh wlan show profile <wifi_nw_name> key=clear

In response check Key Content value under Security Settings

Monday, May 8, 2023

Externalization of Logs from Docker Container

For Docker , if we want to persist any data after the container is removed we can use the following command format:

docker run -d -p 9090:8080 -v <OS File Path>:<Docker container Path> tomcat-test-webapp

Here the logs with be stored in OS file/folder path instead of storing in Docker container path

docker build -t tomcat-test-webapp .

docker run -d -p 9090:8080 -v F:/docker_data/logs:/usr/local/tomcat/logs tomcat-test-webapp

The -v option is used to create volume which persists in OS even after the container is removed.

With container name & Catalina Options it should look like below:

docker run -d --name testDockerWebApp -p 9090:8080 -v F:/docker_data/logs:/usr/local/tomcat/logs -e CATALINA_OPTS="-Xms512M -Xmx512M" tomcat-test-webapp

Format with log, connection pool, properties file externalization:

docker run -d --name <image_name> -p <external_port>:<Docker Internal Port> -v /opt/app_log/<app_name>:/usr/local/tomcat/logs -v /opt/app_cp/<app_name>:/usr/local/tomcat/conf/Catalina/localhost -v /opt/app_prop/<app_name>:/usr/local/properties/<app_name> -e CATALINA_OPTS="-Xms512M -Xmx512M" <docker_hub_image_name>

Friday, March 24, 2023

Deploy WAR file in Docker Container

Pre-requisite: Docker Desktop for Windows to be installed & started

Steps:

Create a WAR file [e.g. TestApp.war]

Create a Dockerfile

Place both of them (WAR & Dockerfile) in same folder (e.g. D:\DevOps)

Navigate to that folder (D:\DevOps) & open command prompt

Run below command to create a image name. Here tomcat-test-webapp is the name of image

docker build -t tomcat-test-webapp .

To run the image use below command

docker run -d -p 8080:8080 tomcat-test-webapp

In case the port to be different use the below structure

docker run -d -p <custom port>:8080 tomcat-test-webapp

Content of Dockerfile

FROM tomcat:9.0.52-jdk8-corretto

COPY ./TestWebApp.war /usr/local/tomcat/webapps

EXPOSE 8080

CMD ["/usr/local/tomcat/bin/catalina.sh","run"]

https://www.youtube.com/watch?v=B9vy3DMHo2I

Pushing Image to Docker Hub

https://www.cloudbees.com/blog/using-docker-push-to-publish-images-to-dockerhub

Pulling Images from Docker Hub & Run

docker login

docker pull <docker_user_name>/tomcat-test-webapp:latest

docker run -d -p 9080:8080 <docker_user_name>/tomcat-test-webapp

In case to run image with memory settings or other Catalin options ; use below command:

docker run -d -p 9080:8080 -e CATALINA_OPTS="-Xms512M -Xmx512M" <docker_user_name>/tomcat-test-webapp

Auto Deploy the changes from Docker Hub:

WATCHTOWER_POLL_INTERVAL is set in sec.

docker run -d --name watchtower -e REPO_USER=<> -e REPO_PASS=<> -e WATCHTOWER_POLL_INTERVAL=30 -e WATCHTOWER_CLEANUP=true -v /var/run/docker.sock:/var/run/docker.sock containrrr/watchtower <container_name>

https://alexgallacher.com/auto-update-docker-containers-by-setting-up-watchtower/

https://containrrr.dev/watchtower/

https://www.geekyhacker.com/how-to-use-spotify-docker-maven-plugin/