Reflection and illegalaccessexception exception during application

First, learn about reflection ：

Reflection ： Encapsulate the components of a class into other objects , This is the reflection mechanism

After the bytecode file is loaded into memory , Will form a Class Class object
Here's how to get Class Three ways of objects ：
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Class.forName(” Full class name “)： Load the bytecode file into memory , return Class object

More for configuration files , You can define the class name in the configuration file . Read the file and load the class

If bytecode file has been loaded into memory , Just pass the class name .Class To get

It is mainly used for parameter passing

An instantiated object already exists , Through the object .getClass() Method ,getClass Method inherited from Object class

It is mainly used for obtaining bytecode of objects

Conclusion ： The same bytecode file （*.class） In a program run , It will only be loaded once , No matter which method you get Class Objects are member methods in the same source code 、 Member variables and constructors will be encapsulated into their corresponding array objects

adopt Class Object can get member variables respectively 、 Member methods and constructors ：

Because the member method 、 The access modifiers of member variables and constructors are different
Different methods of obtaining may lead to the situation that private members cannot be obtained ,
The same thing , After getting the member variable 、 After member methods and constructors , Cannot directly operate on member variables, member methods and constructors modified by private permission modifiers
If you directly operate on the past private members , Will throw out IllegalAccessException abnormal

Solution ： Ignore security checks for permission modifiers

Object obtained .setAccessible(true);
After getting the member method 、 Member variables 、 After the constructor , In the corresponding class method、Field、Constructor You can also further operate on the obtained object .