Java安全-01反射
雷石安全实验室
共 5284字,需浏览 11分钟
·
2022-02-20 22:07
知识基础
类
对象
构造方法
重载
单例模式
动态加载
JVM在执行的时候,并不是一次性把所有的class加载到内存中的,而是用到谁加载谁。
反射的概述
https://www.cnblogs.com/tech-bird/p/3525336.html
Reflection(反射)是Java被视为动态语言的关键,反射机制允许程序在执行期借助于Reflection API取得任何类的內部信息,并能直接操作任意对象的内部属性及方法
获取class对象的三种方式
class.forName("全类名")
类名.class
对象.getClass(),如果上下文存在某个实例对象,可以通过getClass获取他的类
public class re {
public static void main(String[] args) throws ClassNotFoundException, IllegalAccessException, InstantiationException, NoSuchMethodException, InvocationTargetException {
Class cls1 = Class.forName("demo.Person");
Class cls2 = Person.class;
Person person = new Person();
Class cls3 = person.getClass();
System.out.println(cls1);
System.out.println(cls2);
System.out.println(cls3);
System.out.println(cls1==cls2);
System.out.println(cls3==cls2);
}
类“初始化”执行顺序是什么
package demo;
public class test {
public static void main(String[] args) {
Ref ref = new Ref();
}
}
class Ref{
static {
System.out.println("最先执行\r\n");
}
{
System.out.println("第二执行\r\n");
}
public Ref(){
System.out.println("最后执行\r\n");
}
}
demo1
package demo;
public class test {
public static void main(String[] args) throws ClassNotFoundException {
Class.forName("demo.CalcDemo");
}
}
class CalcDemo {
static {
try {
Runtime rt = Runtime.getRuntime();
Process pc = rt.exec("calc");
pc.waitFor();
} catch (Exception e) {
}
}
}
Class方法
获取变量
Field getField(name):根据字段名获取某个public的field(包括父类)
Field getDeclaredField(name):根据字段名获取当前类的某个field(不包括父类)
Field[] getFields():获取所有public的field(包括父类)
Field[] getDeclaredFields():获取当前类的所有field(不包括父类)
cls3.getField("aaa");//指定名称的public修饰的
cls3.getFields();//获取所有public修饰的成员变量
cls3.getDeclaredField("aaaa");//获取所有
cls3.getDeclaredFields();
获取构造方法
cls3.getConstructors();
cls3.getConstructor("aaa");
cls3.getDeclaredConstructor("bbb");
cls3.getDeclaredConstructors();
package demo;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
public class test {
public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
// Ref ref = new Ref();
Class cls = Class.forName("demo.Person");
Constructor constructor = cls.getConstructor();
Constructor constructor1 = cls.getConstructor(String.class);
constructor.newInstance();
constructor1.newInstance("jl");
}
}
demo2
package demo;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.List;
public class test {
public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
Class cls = Class.forName("java.lang.ProcessBuilder");
Method methodStart = cls.getMethod("start");
Constructor constructor = cls.getConstructor(List.class);
Object obj = constructor.newInstance(Arrays.asList("calc.exe"));
methodStart.invoke(obj);
}
}
demo3-可变长参数
package demo;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.List;
public class test {
public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
Class cls = Class.forName("java.lang.ProcessBuilder");
Method methodStart = cls.getMethod("start");
Constructor constructor = cls.getConstructor(String[].class);
Object obj = constructor.newInstance(new String[][]{{"calc.exe"}});
methodStart.invoke(obj);
}
}
获取成员方法
cls3.getConstructors();
cls3.getConstructor("aaa");
cls3.getDeclaredConstructor("bbb");
cls3.getDeclaredConstructors();
demo4
package demo;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
public class test {
public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
// Ref ref = new Ref();
Class cls = Class.forName("demo.Person");
Constructor constructor = cls.getConstructor();
Constructor constructor1 = cls.getConstructor(String.class);
constructor.newInstance();
constructor1.newInstance("jl");
}
}
demo5
package demo;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
public class test {
public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, InvocationTargetException, IllegalAccessException {
Class cls = Class.forName("java.lang.Runtime");
Method method = cls.getMethod("exec", String.class);
Method method1 = cls.getMethod("getRuntime");
method.invoke(method1.invoke(cls),"calc.exe");
}
}
Runtime类就是单例模式,我们只能通过 Runtime.getRuntime() 来获取到 Runtime 对 象。
往期回顾
小程序测试流
ModSecurity 搭建web安全防火墙和流量检测
评论