java The reflection mechanism is implemented through the following mechanisms: The reflection API provides interfaces and classes for accessing and manipulating reflection data. The JVM maintains an internal data structure that contains metadata for all loaded classes. The reflection mechanism performs introspection operations by accessing this data.
The principle of Java reflection mechanism
The Java reflection mechanism allows programs to inspect and modify the structure and behavior of Java classes at runtime. It provides an introspection capability that enables us to load classes, create objects, call methods and get or set field values.
Principle
The reflection mechanism is implemented through the following mechanism:
Class
and Method
, are used to access and manipulate reflected data. Usage
To use the reflection mechanism, you need to use the Class
class. Class
The object represents the class being inspected or modified. The Class
object can be obtained as follows:
ClassName.class
, for example: String.class
Class.forName("ClassName")
Object.getClass()
Practical case
The following is an example of creating an object and calling its methods through the reflection mechanism:
import java.lang.reflect.Class; import java.lang.reflect.Method; public class ReflectionDemo { public static void main(String[] args) throws Exception { // 获取 String 类 Class<?> stringClass = String.class; // 创建 String 对象 Object stringObject = stringClass.newInstance(); // 获取 concat 方法 Method concatMethod = stringClass.getMethod("concat", String.class); // 调用 concat 方法 String result = (String) concatMethod.invoke(stringObject, "World"); // 打印结果 System.out.println(result); // 输出: HelloWorld } }
In this example, we obtain String# through
String.class ## The
Class object of the class. Then, use
newInstance() to create a
String object. Next, get the
Method object of the
concat() method and call it, passing an argument and getting the result.
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