If we had a few dozen POJOs, the code generation capabilities of the annotation processor would save us a lot of time by creating the corresponding builder files at compile time.īy fully leveraging the power of annotation processing we will be able to skip a lot of repetition and save a lot of time. A builder is a design pattern in Java that is used to provide a better alternative to constructors when there is a large number of parameters involved or there is a need for multiple constructors with optional parameters. We can further use the power of annotation processing to perform more complex automated tasks such as creating builder source files for a set of POJOs at compile time. We did an overview of annotations, followed by a simple real-world example of annotation processing.
So we verified that test2(), which did not have the annotation, did not have its output printed. Finally, we perform a runtime invocation of the methods that were identified as being annotated with want to verify the test1() method will run since it is annotated with and test2() will not run since it is not annotated with output is: Then, we’re iterating through the methods and checking each method if it is annotated with the annotation. Public class ParentClass īy calling getDeclaredMethods(), we’re getting the methods of our AnnotatedMethods class. Let’s look at the annotation as an example: It simply provides information that can be used at compile time or runtime to perform further processing. We can further extend the core functionality to provide our custom annotations.Īn annotation by itself does not perform any action.
Some common examples of annotations are and These are built-in annotations provided by Java through the java.lang package. This article is accompanied by a working code example on GitHub.Īn annotation is preceded by the symbol. In this article, we will discuss the topic of annotations and demonstrate the power of annotation processing with a real-world example. The java.lang package provides some core annotations and also gives us the capability to create our custom annotations that can be processed with annotation processors. An annotation processor processes these annotations at compile time or runtime to provide functionality such as code generation, error checking, etc. Annotations provide information to a program at compile time or at runtime based on which the program can take further action.
An annotation is a construct associated with Java source code elements such as classes, methods, and variables.
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