Writing custom annotation
We can annotate classes, interface, methods, parameters and even packages also. In this tutorial, we're going to focus on how to create custom annotations, and how to process them.
Before we proceed, it is important to note that adding the JsonField annotations does not change the runtime behavior of the Car class.
Java custom method annotation
How compiler understand this? How Are Annotations Used? Processing Annotations Using Reflection Till now, we have only created the annotation and then used it. For example, if the field and constructor targets are associated with an annotation, then the annotation may be used on either fields or constructors. For example, if we create a car class, we can annotate the fields of the car such as make and model with our annotation. This is a very important step since the fields we annotated are private. While annotations should not be used in place of interfaces or other language constructs that properly accomplish a task in an object-oriented manner, they can greatly simplify repetitive logic. Applying this annotation to a method or constructor suppresses unchecked warnings about a non-reifiable variable arity vararg type and suppresses unchecked warnings about parameterized array creation at call sites. Processing Annotations So far, we have seen how to create custom annotations and how to use them to decorate the Person class. We can read more about annotations in our article on annotation basics. Method Level Annotation Example Let's imagine that, before serializing an object to a JSON string, we want to execute some method to initialize an object. Therefore, unless the inclusion of an annotation parameter name in a single-element annotation adds to the readability of code, it should be omitted.
You saw an example above. In java, you have to use reflection API to access annotations on any type i. A family guy with fun loving nature. Moreover, we want the initNames method to be called before serialization.
For example, rather than creating a toJsonStringmethod within an interface and having all classes that can be serialized implement this interface, we can annotate each serializable field.
For the sake of simplicity, we will assume that this annotation will be used only for fields of type String, ensuring that the value of the field can be directly serialized as a string.
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