java的反射手写示例代码

首先创建需要动态加载的类

package classloader;

public class TestClass {
    private String value;
    public TestClass() {
        value = "123";
    }
    public void publicMethod(String s) {
        System.out.println("i love " + s);
    }
    private void privateMethod() {
        System.out.println("value is " + value);
    }
}

 

通过反射加载类

package classloader;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

public class Main {
    public static void main(String[] args) throws ClassNotFoundException, IllegalAccessException, InstantiationException, NoSuchMethodException, InvocationTargetException, NoSuchFieldException {
        // 获取TestClass类的Class对象
        Class<?> testClass=Class.forName("classloader.TestClass");
        // 创建TestClass类实例
        TestClass testClassObject= (TestClass) testClass.newInstance();
        // 获取Class类的方法
        Method[] methods=testClass.getDeclaredMethods();
        for (Method method : methods) {
            System.out.println(method);
        }
        // 获取指定方法并调用
        Method publicMethod = testClass.getDeclaredMethod("publicMethod",
                String.class);
        publicMethod.invoke(testClassObject,"zhanghs");
        //获取指定参数并对参数进行修改
        Field field = testClass.getDeclaredField("value");
        //私有变量取消安全检查
        field.setAccessible(true);
        field.set(testClassObject,"zhanghaos");
        // 调用 private 方法
        Method privateMethod=testClass.getDeclaredMethod("privateMethod");
        //私有方法也需取消安全检查
        privateMethod.setAccessible(true);
        privateMethod.invoke(testClassObject);
    }
}