详解Java如何利用反射提高代码的灵活性

public class ReflectionDemo {
    public static void main(String[] args) {
        // 获取类的Class对象
        Class<?> clazz = String.class;
        // 获取类的名称
        String name = clazz.getName();
        System.out.println("类的名称：" + name);
        // 获取类的方法
        Method[] methods = clazz.getMethods();
        System.out.println("类的方法：");
        for (Method method : methods) {
            System.out.println(method.getName());
        }
        // 获取类的属性
        Field[] fields = clazz.getFields();
        System.out.println("类的属性：");
        for (Field field : fields) {
            System.out.println(field.getName());
        }
    }
}

public interface Hello {
    void sayHello(String name);
}
public class HelloImpl implements Hello {
    @Override
    public void sayHello(String name) {
        System.out.println("Hello, " + name + "!");
    }
}
public class HelloProxy implements InvocationHandler {
    private Object target;
    public HelloProxy(Object target) {
        this.target = target;
    }
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("Before method " + method.getName());
        Object result = method.invoke(target, args);
        System.out.println("After method " + method.getName());
        return result;
    }
}
public class DynamicProxyDemo {
    public static void main(String[] args) {
        Hello hello = new HelloImpl();
        InvocationHandler handler = new HelloProxy(hello);
        Hello proxy = (Hello) Proxy.newProxyInstance(hello.getClass().getClassLoader(),
                hello.getClass().getInterfaces(), handler);
        proxy.sayHello("World");
    }
}

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface Log {
}
public class LogProcessor {
    public static void process(Object target) {
        Class<?> clazz = target.getClass();
        Method[] methods = clazz.getMethods();
        for (Method method : methods) {
            if (method.isAnnotationPresent(Log.class)) {
                System.out.println("Method " + method.getName() + " is annotated with @Log");
            }
        }
    }
}
public class LogDemo {
    @Log
    public void sayHello(String name) {
        System.out.println("Hello, " + name + "!");
    }
    public static void main(String[] args) {
        LogDemo demo = new LogDemo();
        LogProcessor.process(demo);
    }
}