Using NotNull Annotation in method argument
Quick note: @NotNull
won’t pull a Rambo and defend itself until runtime with a bean validation implementation like Hibernate Validator is rallied within a Spring context (e.g., in a Spring MVC controller armed with @Validated
).
Making sense of @NotNull
In the wild world of Java, @NotNull
is a tool that developers wield to fend off contradictory Null
values. It's a shiny badge that politicians (developers and validation frameworks) wear to signify that null values are persona non grata.
The three-step dance to @NotNull
The route from null chaos to @NotNull
nirvana involves three moves:
- Grab your dancing shoes (add a validation provider dependency) for your build tool (like Maven or Gradle).
- Mark your dance floor (place the
@NotNull
annotation where it fits like a glove in your code). - Do the dance (enable validation): This could be prancing to the beat of
@Validated
in a Spring application or performing the tango with aValidatorFactory
and aValidator
.
Lombok's magic wand
Lombok has a neat parlor trick up its sleeve. Its @NonNull
annotation instantly spawns a null check, throwing a NullPointerException
before anyone notices, saving you from the potential of stepping on a NullPointerException
landmine later on.
Your custom validation kingdom
With the power of ConstraintValidator
interface, you can establish your kingdom's validation constitution. This allows the customization of the validation routine, leading to an intricate and efficient system.
The code proclamation
By decree of the @NotNull
, all developers shall know the expectation is to never pass a null value. This is a decree that resonates throughout the kingdom (the entire codebase).
Manual validation - the rite of passage
For those who want a personal touch, or for when the automatic validation is catching some Z's, manual validation rises to the occasion. Using a Validator
instance, you can check the pulse of constraint violations with a handy validate
method.
The null check - the shield against NPEs
Merely adding a @NotNull
proclamation provides no assurance against null values. A true guardian requires an additional null check, either manually or through a trusty steward, Lombok, or a structured framework. An unverified @NotNull
is as effective as screen doors on a submarine.
The art of null management
Beyond just @NotNull
, here are additional methods to marshall nulls in your Java codebase:
Objects.requireNonNull - the bouncer's bodyguard
Pair @NotNull
with Objects.requireNonNull()
for immediate reveal of null values:
Popping the @Validated champagne in Spring
In a Spring application, you can trigger automatic validation using @Validated
. It's like popping the champagne bottle as soon as the party starts, giving meaningful and immediate feedback to the guests (caller).
Teaming up with the Validator squad
There may be instances where you need to perform a roll call check on objects. You can do this with a ValidatorFactory
and a Validator
instance:
Forming your custom validator band
For advanced enforcing, you can implement ConstraintValidator
to customize validation alignment with complex rules:
This enables your application to march to the beat of complex business rules while still keeping focus on basic non-null values.
Navigating the maze of edge cases
Collections and arrays - don't be fooled
In the world of collections and arrays, @NotNull
can be deceiving. It doesn't guarantee that the contents are also non-null or non-empty. A more elaborate method or custom validator could be your map to navigate the maze.
The interface-implementation dichotomy
The implementation of @NotNull
may play tricks depending on the validation provider. A switch in the provider could potentially change the nature of your validation strategy.
The power of external magic (libraries)
The essence of @NotNull
lies in the power of external libraries like Hibernate Validator or JSR 303/JSR 380 Bean Validation APIs. Remember to integrate them well into your application to amplify the power of @NotNull
.
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