Brief introduction of reflection mechanism

Reflection is Java Seen as the key to dynamic language , The reflection mechanism allows programs to use reflection during execution API Get internal information about any class , And can directly operate the internal properties and methods of any object .
obtain Class Common methods of objects ：

Class c=Class.forName("java.lang.String");

Even if it's private Modified keywords can also be read .
function ：
1） Judge the member variables and methods of any class at run time ;
2） Get generic information at runtime ;
3） Processing annotations at run time ;
4） Generate dynamic agents ;
5） At run time, determine the class that any object belongs to ;
6） Construct an object of any class at run time ;

• instanceof Used to determine whether it is an instance of a class ：

System.out.println(Class.forName(properties.getProperty("FactoryName")).newInstance() instanceof IFactory );

• Use newInstance() Method to create Class Object corresponds to an instance of the class .

IFactory operFactory = (IFactory) Class.forName("AddFactory").newInstance();

• Advantages and disadvantages ：
  advantage ：
  1） It improves the flexibility and expansibility of the program , Reduce module coupling ;
  2） Get the various contents of the class at run time , Method of calling object .
  3） Using reflection prevents code from being written dead in the framework .
  shortcoming ：
  1） Reflection consumes a certain amount of system resources , The efficiency of reflection operation is much lower than that of normal operation ;
  2） The permission check can be ignored when the reflection calls the method , As a result, encapsulation may be broken and security problems may arise .