This will tell the IDE that the field can be null in some cases, so no need to trigger an alarm. We can express our intention using the annotation on the field. But as per our safety checks, the IDE thinks it cannot be. There could be scenarios where a particular field can be null (no matter how much we want to avoid it).įor example, the pastEmployment field could be nullable in the Employee class (for someone who hasn’t had previous employment). Shows a warning if any of the parameters or return values are null for the applied here is a catch. Here is a quick summary for Annotated element We can see the IDE is now warning us about the non-nullable return value:

Package io.reflectoring.nullsafety // imports

Let’s use a plain Employee class to understand the annotations: IntelliJįor IntelliJ, we can activate the annotation checking under ‘Build, Execution, Deployment -> Compiler’: Eclipseįor Eclipse, we can find the settings under ‘Java -> Compiler -> Errors/Warnings’: Example Code If you don’t see the relevant warning, check the compiler settings in your IDE. Please note that not all development tools can show these compilation warnings. The Spring Boot starter is all we need, no need to add any extra dependencies. To create the base project, we can use the Spring Initializr. Let us find out more with some code examples.

We are going to use IntelliJ IDEA in this tutorial. They can warn developers of potential issues during compile time.

IDEs like Eclipse and IntelliJ IDEA can understand these annotations.

Under the Spring core package, there are 4 such annotations: This article is accompanied by a working code example on GitHub. In this article, we will learn how to use these annotations to write null-safe code using Spring Boot.

Luckily, Spring Framework offers some annotations to solve this exact problem. Java’s type system does not have a way to quickly eliminate the dangerous null object references. Since NullPointerException is a runtime exception, it would be hard to figure out such cases during code compilation. Null-safety ensures that we have added proper checks in the code to guarantee the object reference cannot be null or possible safety measures are taken when an object is null, after all. We can find plenty of articles on the internet explaining how to write null-safe code. NullPointerExceptions (often shortened as “NPE”) are a nightmare for every Java programmer.

Kotlin null safety