Java

Java was the first programming language I was taught at University, and the language I used for the first decade of my career. It continues to be a reliable companion throughout my software development career. Unfortunately, not having developed with Java professionally for several years, I’ve found there are many aspects of the modern Java language that I’m simply not familiar with. To rectify this, I’ve collected the major improvements to the language beginning with Java 8, combined with a short explanation of how they work and how to use them. It assumes you know Java, but don’t really know Java. Hopefully, it can take you from experienced beginner to just plain experienced again. ...

Spring Data REST combines the features of Spring Data with Spring HATEOAS to make it easy to build hypermedia-driven REST APIs on top of Spring Data repositories. The basic functionality provided out of the box creates and exposes simple REST endpoints for performing CRUD operations on Spring Data repositories. For a lot of use cases, this is entirely enough functionality to meet your needs. In other cases, you need to extend the REST API to include additional functionality that isn’t provided by Spring Data REST and it can be difficult to determine exactly how to do this. In this blog post, I show you how to augment a Spring Data REST API with additional endpoints to turn a basic CRUD API into a full featured web service. ...

When working with Spring Boot, some auto-configuration can happen seemingly by magic. For example, in a traditional Spring application with Java-based configuration, you might configure an H2 database using the following block of code to set the type of the database and run some scripts to initialize it: @Bean public DataSource dataSource() { return new EmbeddedDataSourceBuilder() .setType(H2) .addScript("taco_schema.sql") .addScripts("user_data.sql", "ingredient_data.sql") .build(); } With Spring Boot, you can remove this entire block of code and use auto-configuration. If the H2 dependency is available in the classpath, Spring Boot will automatically create the DataSource and add it as a Bean to Spring’s application context and apply SQL scripts as long as they are named schema.sql or data.sql. Spring Boot does this auth-configuration by leveraging the Spring environment that collects the set of properties available to a Java application and uses those properties to configure beans in Spring’s application context. The following figure from Spring in Action shows how the Spring environment is generated by some of the available configuration property sources available in a typical Java application. ...

I’m a fan of Java. If you haven’t given it a chance in a while, you may not have noticed that, Java has quietly been adopting some of the best practices that make dynamic and functional languages so appealing, without sacrificing the many hundred person-years of effort that have made Java and the JVM a world-class development environment. Java is still one the world’s most popular programming languages with roughly 9 million programmers using Java. It doesn’t make sense to ignore all of that history and development effort because of a niggling feeling that Java is a little too verbose, or that XML is so last year. ...

Inversion of Control (IoC), also known as Dependency Injection (DI), allows an object to define their dependencies as constructor arguments (strictly speaking, you can set these dependencies as properties, but the examples I will use today are constructor-based). This is the inverse of the object itself controlling the instantiation or location of its dependencies, hence the name Inversion of Control. Let’s look at an example from Stackoverflow using a text editor with a spell checking component: ...

As someone who is being recently re-introduced to the Java platform, there are a lot of components and pieces to become familiar with. One of those pieces is OSGi, a service registry and deployment specification for Java apps. The OSGi specification describes a complete environment for running Java applications as components. Each component is a bundle that can be remotely installed, started, stopped, updated or uninstalled. In addition, OSGi provides a service registry that allows existing services to detect the addition or removal of other services and adapt accordingly. ...

Testing concurrent objects can be challenging. One particular pattern that is useful for objects used in producer-consumer designs is to ensure that everything put in to a shared concurrent queue by a producer is correctly executed by consumers. ...

Have you come across the misfortune of needing to auto-generate Java source code? Luckily, anything you’ve wanted to do with Java has already been done — and auto-generating Java is no different. I recently used JCodeModel to translate from JSON to Java — it worked great but it lacks any tutorial-style documentation. This article means to fill that gap. If you feel the need to go more in-depth, consult the the Javadoc. ...

Whenever I tell people I’ve been working with Java I get the same reaction: “Yuck! Java? Why Java?” And, admittedly, I had the same reaction — at first. But over time, I’ve come to appreciate Java for its type safety, performance, and rock-solid tooling. I’ve also come to notice that this isn’t the Java I was used to — it’s been steadily improving over the last ten years. ...

Lately I’ve been tasked with developing a Java library for internal use. For testing, its proved useful to package the library for local use. This article describes how to add a Jar file to a local Maven repository for use in your own testing and development. Create your local Maven repository Your local Maven repository lives within the project you are developing for. Creating your local repository is as simple as making a new directory. ...