How does the Java reflection mechanism work with the reflector itself?

Java reflection mechanism allows exploring the reflector itself, and annotations on the Method object can be obtained through reflection, including annotation type and value.

Java reflection mechanism is used in the reflector itself

Java reflection mechanism allows the program to inspect and modify the structure of the class at runtime, But it is rarely used to explore the reflection mechanism itself. This article will use a practical case to show how to use the reflection mechanism to study the operation of the reflector.

Case: Get theAnnotationon the

object. We can use reflection to get theMethodAnnotations attached to the object. Here is the sample code:

import java.lang.annotation.Annotation; import java.lang.reflect.Method; public class Main { public static void main(String[] args) { try { // 获取 Method 对象 Method method = Main.class.getMethod("annotatedMethod"); // 使用反射获取注解 Annotation[] annotations = method.getAnnotations(); // 遍历并打印注解 for (Annotation annotation : annotations) { System.out.println(annotation); } } catch (NoSuchMethodException e) { e.printStackTrace(); } } @MyAnnotation("Hello, World!") public void annotatedMethod() { } }

Result:

@MyAnnotation(value=Hello, World!)

Parsing:

• We first useMain.class.getMethod("annotatedMethod")Gets theMethodobject of theannotatedMethodmethod of theMainclass.
• Then we usemethod.getAnnotations()to get all the annotations on the method and store them in theannotationsarray.
• Finally, we loop through theannotationsarray and print the type and value of each annotation.

This example shows how to use the reflection mechanism to obtain the annotations on theMethodobject. The same principle can be used to explore any other aspect of the reflection mechanism, for example:

• Get the parent class and interface of the class
• Get the type and value of the field
• Modify the attributes of the class (such as access rights)

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