Java反射学习(一)

以前不知道为什么安装jdk后，程序就会执行。老土的话说是：安装了Java虚拟机，最近看到相关的文章，说是类加载器实现了类加载。

测试代码如下：

@Test
public void getPerson() throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
ClassLoader loader = Thread.currentThread().getContextClassLoader();
Class clazz =loader.loadClass("com.cn.Person");
Constructor constructor = clazz.getDeclaredConstructor((Class[]) null);
Person person = (Person) constructor.newInstance();
Method[] methods = clazz.getMethods();
for(int i=0;i<methods.length;i++){
// System.out.println(methods[i]);
}
Method[] methods1 = clazz.getDeclaredMethods();
for (int i=0;i<methods1.length;i++){
// System.out.println(methods1[i]);
}
/*
设置属性的值
*/
Method method = clazz.getMethod("setAge",int.class);
method.invoke(person,10);

// System.out.println(person.getAge());
Method method1 = clazz.getMethod("say");
method1.invoke(person);

}
@Test
public void getClassLoader(){
ClassLoader classLoader =Thread.currentThread().getContextClassLoader();
System.out.println(classLoader);
System.out.println(classLoader.getParent());
System.out.println(classLoader.getParent().getParent());
}

提到了几个重要的反射相关的类：classLoader     class    constructor     method。
涉及到的类加载器：   根类加载器      ExtClassLoader    AppClassLoader