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Secret Key and String Conversion in Java
1. Overview In a real-life scenario, we come across several situations where we need encryption and decryption for security purposes. We can achieve this easily using a secret key. So for encrypting...
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How to Return Multiple Entities In JPA Query
1. Overview In this short tutorial, we'll see how to return multiple different entities in JPA Query. First, we'll create a simple code example containing a few different entities. Then, we'll explain...
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Finding All Classes in a Java Package
1. Overview Sometimes, we want to get information about the runtime behavior of our application, such as finding all classes available at runtime. In this tutorial, we'll explore several examples of...
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Writing an Enterprise-Grade AWS Lambda in Java
1. Overview It doesn't require much code to put together a basic AWS Lambda in Java. To keep things small, we usually create our serverless applications with no framework support. However, if we need...
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Find All Numbers in a String in Java
1. Overview Sometimes we need to find numeric digits or full numbers in strings. We can do this with both regular expressions or certain library functions. In this article, we'll use regular...
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Attach and Detach From a Docker Container
1. Overview While working with a docker container, we often need to run it in an interactive mode. This is where we attach the standard input, output, or error streams of our terminal to the container....
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Defining Unique Constraints in JPA
1. Introduction In this tutorial, we'll discuss defining unique constraints using JPA and Hibernate. First, we'll discuss unique constraints and how they differ from primary key constraints. Next,...
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Project Reactor: map() vs flatMap()
1. Overview This tutorial introduces the map and flatMap operators in Project Reactor. They're defined in the Mono and Flux classes to transform items when processing a stream. In the following...
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Kafka Streams vs. Kafka Consumer
1. Introduction Apache Kafka is the most popular open-source distributed and fault-tolerant stream processing system. Kafka Consumer provides the basic functionalities to handle messages. Kafka Streams...
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Java Weekly, Issue 388
1. Spring and Java >> Taming Resource Scopes [inside.java] Exploring different approaches to make the Foreign Memory Access/Linker API safer – an interesting glimpse on the future of natives in...
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Exclusions from Jacoco Report
1. Introduction In this article, we'll see how to exclude certain classes and packages from JaCoCo test coverage reports. Generally, the candidates for exclusion can be configuration classes, POJOs,...
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Spring Boot Error ApplicationContextException
1. Overview In this quick tutorial, we're going to take a close look at the Spring Boot error “ApplicationContextException: Unable to start ServletWebServerApplicationContext due to missing...
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Log4j Warning: “No Appenders Could Be Found for Logger”
1. Overview In this tutorial, we'll show how to fix the warning, “log4j: WARN No appenders could be found for logger”. We'll explain what an appender is and how to define it. Furthermore, we will show...
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Creating, Updating and Deleting Resources with the Java Kubernetes API
1. Introduction In this tutorial, we'll cover CRUD operations on Kubernetes resources using its official Java API. We've already covered the basics of this API usage in previous articles, including...
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Feign Logging Configuration
1. Overview In this tutorial, we'll describe how we can enable Feign client logging in our Spring Boot application. Also, we'll take a look at different types of configurations for it. For a refresher...
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Spring Validation in the Service Layer
1. Overview In this tutorial, we’ll discuss Spring validation in the service layer of a Java application. Although Spring Boot supports seamless integration with custom validators, the de-facto...
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Understanding the Pattern.quote Method
1. Overview When using regular expressions in Java, sometimes we need to match regex patterns in their literal form – without processing any metacharacters present in those sequences. In this quick...
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Inserting Null Into an Integer Column Using JDBC
1. Introduction In this article, we'll examine how we can store null values in our database using plain JDBC. We'll start by describing the reasons for using null values, followed by several code...
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Interface With Default Methods vs Abstract Class
1. Introduction After the introduction of default methods in Java interfaces, it seemed that there was no longer any difference between an interface and an abstract class. But, that's not the case —...
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Max-HTTP-Header-Size in Spring Boot 2
1. Overview Spring Boot web applications include a pre-configured, embedded web server by default. In some situations, though, we'd like to modify the default configuration to meet custom requirements....
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