The Java class library uses the "Reflections" framework to obtain instance analysis of the annotation information
In the Java class library, the annotation information can be easily obtained by using the "Reflections" framework.This article will introduce how to use the framework to obtain the annotation information through an example analysis.
Java's "Reflections" framework is a powerful library that allows us to obtain and operate metadata of Java class during runtime.Using this framework, we can easily obtain the annotation information in the code, which is very useful for achieving some specific needs.
First, we need to introduce the dependence of the "Reflections" framework in the project.It can be achieved by adding the following dependencies in Maven or Gradle:
Maven:
<dependency>
<groupId>org.reflections</groupId>
<artifactId>reflections</artifactId>
<version>0.9.12</version>
</dependency>
Gradle:
groovy
implementation 'org.reflections:reflections:0.9.12'
Next, let's look at a simple example to demonstrate how to use the "Reflections" framework to get the annotation information.
Suppose we have a comment`@myannotation`, it can be used to mark a certain class:
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotation {
String value();
}
Then we use the annotation in a class:
@MyAnnotation("Example")
public class MyClass {
// Class implementation content
}
Next, we use the "Reflections" framework to obtain the annotation information on the `MyClass` class:
import org.reflections.Reflections;
import java.util.Set;
public class AnnotationExample {
public static void main(String[] args) {
Reflections reflections = new Reflections("your.package.name");
Set<Class<?>> annotatedClasses = reflections.getTypesAnnotatedWith(MyAnnotation.class);
for (Class<?> annotatedClass : annotatedClasses) {
MyAnnotation annotation = annotatedClass.getAnnotation(MyAnnotation.class);
System.out.println(annotatedClass.getName() + " has annotation value: " + annotation.value());
}
}
}
In the above code, we first created a Reflections object and specified the package name to be scanned.Then, use the collection of categories with `GettypesannotatedWith` to obtain a class with a category with the` Myannotation`.Finally, we traverse each of the classes with annotations, and use the `Getannotation` method to obtain an example of the annotation, and print the value of the annotation.
Through the above code, we can output class names and annotations on the console.
In summary, using the "Reflections" framework can easily obtain annotations of the Java class. This framework provides a set of powerful tools that allows us to obtain and operate metadata at runtime.Through the above example analysis, we can flexibly use the framework to meet various needs.
