Kotlin

Kotlin + Spring Boot CRUD examples:

Kotlin + Spring Boot with Template Engines CRUD examples:

Build REST APIs with Kotlin + Spring Boot:


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Learn Java 8 streams with an example - print odd/even numbers from Array and List

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Example 1: Java 8 program to print odd numbers from a List import java.util.Arrays; import java.util.List; import java.util.stream.Collectors; /*Java 8 Program to find Odd Numbers from a List*/ public class DriverClass { public static void main( String [] args) { List < Integer > numbers = Arrays. asList( 1 , 4 , 8 , 40 , 11 , 22 , 33 , 99 ); List < Integer > oddNumbers = numbers.stream(). filter(o -> o % 2 != 0 ). collect(Collectors.toList()); System.out.println(oddNumbers); } } Spring Boot + Angular 10 + Mongo DB CRUD Example - click here Example 2: Java 8 program to print even numbers from a List import java.util.Arrays; import java.util.List; import java.util.stream.Collectors; /*Java 8 Program to find Even Numbers from a List*/ public class DriverClass { public static void main( String [] args) { List &l
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Java Stream API - How to convert List of objects to another List of objects using Java streams?

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Hello everyone, here we will show you how to convert a List of objects to another List of objects in Java using the Java streams map(). The ‘map’ method maps each element to its corresponding result.   Java Stream API The Java Stream API provides a functional approach to processing collections of objects. The Stream in Java can be defined as a sequence of elements from a source Collection or Array. Most of the stream operations return a Stream. This helps create a chain of stream operations(stream pipe-lining). The streams also support the aggregate or terminal operations on the elements. for example, finding the minimum or maximum element or finding the average etc...Stream operations can either be executed sequentially or parallel. when performed parallelly, it is called a parallel stream. Stream map() Method The Java 8 Stream map() is an intermediate operation.It converts Stream<obj1> to Stream<obj2>. For each object of type obj1, a new object of type obj2 is created and
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Registration and Login with Spring Boot + Spring Security + Thymeleaf

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Hello everyone, I hope you all are well, today we will learn how to create user registration and login using Spring boot,  Spring security,  Thymeleaf, JPA, and H2DB . The  GitHub repository link is provided at the end of this tutorial. You can download the source code. Technologies used: Spring Boot 2.5.5  Spring Data JPA Spring Security  Thymeleaf  Maven 3+ Java 17  H2 Database User Interface User Registration Authentication Failed Authentication success Sign out Project Structure: Maven[pom.xml]: A Project Object Model or POM is the fundamental unit of work in Maven. It is an XML file that contains information about the project and configuration details utilized by Maven to build the project. It contains default values for most projects. Some of the configurations that can be designated in the POM is the project dependencies, the plugins or goals that can be executed, the build profiles, and so on. Other information such as the project version, description, developers, mailing lists
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Java, Spring Boot Mini Project - Library Management System - Download

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Hello everyone, Hope you are doing well. Here, we provide a Library Management System mini-project for beginners, it's free for download. Maybe you can build more on top of this project and create your own product, that's all about you. The source code download link is provided at the end of this post. 1. Benefit of this project You could cover the following technologies and features by learning and debugging this mini project. Java 17 Java Stream Java Lamda Expressions Java Records Functional programming Object-oriented programming var Keyword in Java Generics in Java Java Switch Spring boot 2.6.4 Spring Security Thymeleaf template engine OpenCSV Spring Data JPA Server Side Pagination H2 Database  Bootstrap HTML CSS and more... 2. Objective Of Spring Boot On Library Management System The main objective of this project is to manage the details of the books, author, category, and publisher. Only Admin/Librarian will manage all these activities. Also, they can export the data in
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Spring Boot + Mockito simple application with 100% code coverage

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In this article, we will show you a simple  Spring Boot example to demonstrate test methods for Controllers, Service, and Repository, And code coverage analysis using the EclEmma plugin. Technologies used: Spring Boot 2.6.4 Mockito 3.11.2 Maven 3+ EclEmma plugin Junit 5 Java 17 A quick overview of  Spring Boot, Mockito, and EclEmma plugin Spring boot: Spring boot to develop REST web services and microservices. Spring Boot has taken the Spring framework to the next level. It has drastically reduced the configuration and setup time required for spring projects. We can set up a project with almost zero configuration and start building the things that actually matter to your application. Mockito: Mockito is a mocking framework, a JAVA-predicated library that is utilized for efficacious unit testing of JAVA applications. Mockito is utilized to mock interfaces so that a dummy functionality can be integrated into a mock interface that can be utilized in unit testing. EclEmma : E
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ReactJS, Spring Boot JWT Authentication Example

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Hello everyone, In this tutorial, we’ll create a user registration & login example using ReactJS, Spring Boot, Spring Security, and JWT authentication. You could download the source code from our Github repository, the download link is provided at the end of this tutorial. Technologies used Backend Technologies: Java 17 Spring Boot 2.7.0 Spring Security Spring Data JPA JWT H2 Database Frontend Technologies: React 17.0.1 Axios 0.27.2 Redux 4.0.5 Bootstrap 4.5.2 ReactJS - SpringBoot - JWT - Flow Backend Project Directory: Frontend Project Directory: Following is the screenshot of our application - User Registration: User Signin: Profile View: Access Resource: We will build two projects:  1. Backend:   spring-boot-security-jwt 2. Frontend: react-redux-jwt Project 1: spring-boot-security-jwt Pom.xml <?xml version = "1.0" encoding = "UTF-8" ?> <project xmlns = "http://maven.apache.org/POM/4.0.0" xmlns:xsi = "http://www.w3.org/2001/XMLSchem
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Spring boot video streaming example-HTML5

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Hello everyone, Today we will learn how to stream MP4 video using Spring Boot and Spring Web Flux.  The Source code download link is provided at the end of this post. New, Quarkus Practice User Interface   Project Structure: G radle(build.gradle) plugins { id 'org.springframework.boot' version '2.5.4' id 'io.spring.dependency-management' version '1.0.11.RELEASE' id 'java' } group = 'com.knf.demo' version = '0.0.1-SNAPSHOT' sourceCompatibility = '11' repositories { mavenCentral() } dependencies { implementation 'org.springframework.boot:spring-boot-starter-webflux' testImplementation 'org.springframework.boot:spring-boot-starter-test' testImplementation 'io.projectreactor:reactor-test' } test { useJUnitPlatform() } Service (VideoStreamingService.java) package  com.knf.demo.service ; import org.springframework.beans.factory.annotation. Autowired ; import org.springframew
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Top 5 Java ORM tools - 2023

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  ORM stands for object-relational mapping, where objects are acclimated to connect the programming language on to the database systems, with the facility to work with SQL and object-oriented programming concepts. It is feasible for ORM to be implemented on any type of database management system where object mapping to the table can be achieved in the virtual system. There are many types of ORM tools in Java, which are listed below: 1. Hibernate Hibernate is an open-source, non-invasive, lightweight java ORM(Object-relational mapping) framework to develop objects which are independent of the database software and make independent persistence logic in all JAVA, JEE. It provides some abstraction layer, meaning that the developers do not have to worry about the implementations, Hibernate does the implementations for us internally like Establishing a connection with the database, writing queries to perform CRUD operations, etc. It is used to develop persistence logic. Persistence logic mea
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Java - Blowfish Encryption and decryption Example

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Blowfish is a symmetric-key block cipher, designed in 1993 by Bruce Schneier and included in many cipher suites and encryption products. Blowfish provides a good encryption rate in software and no effective cryptanalysis of it has been found to date. However, the Advanced Encryption Standard (AES) now receives more attention, and Schneier recommends Twofish for modern applications. Example 1: Encryption and decryption using Blowfish import java.io.UnsupportedEncodingException; import java.nio.charset.Charset; import java.security.InvalidKeyException; import java.security.NoSuchAlgorithmException; import java.util.Base64; import javax.crypto.BadPaddingException; import javax.crypto.Cipher; import javax.crypto.IllegalBlockSizeException; import javax.crypto.NoSuchPaddingException; import javax.crypto.spec.SecretKeySpec; /** * This program demonstrates how to encrypt/decrypt * input using the Blowfish * Cipher with the Java Cryptography. */ public class BlowfishDemo { p
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Custom Exception Handling in Quarkus REST API

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Hello everyone, In this article, we will learn how to handle exceptions in the Quarkus REST application using ExceptionMapper interface implementations. ExceptionMapper is a contract for a provider that will map a thrown application exception to a Response object. We will show you custom exception handling with the help of a simple application, Project Directory: application.properties knowledgefactory.custom.error.msg.usernotfound = User not found knowledgefactory.custom.error.msg.badrequest.numeric = User Id must be numeric Create Error Message package org.knf.dev.demo.exception; public class ErrorMessage { private String message; private Boolean status; public String getMessage() { return message; } public void setMessage( String message) { this .message = message; } public Boolean getStatus() { return status; } public void setStatus( Boolean status) { this .status = status; } public Erro
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