Java Reflection Classic Summary

1: Parse the constructor of this class by reflection

public class Person {public String name= ' Jack ';p rivate int password=123;private static int age;public person () {System.out . println ("person");} Public person (String name) {System.out.println ("person Name:" +name);} Public person (String Name,int age) {System.out.println (' Person name: ' +name+ ' person ' Age: ' +age);} Private person (List list) {System.out.println (' person list ');} public void aa () {System.out.println ("AA");} public void Aa1 (String name,int age) {System.out.println ("Name:" +name+ "Age:" +age);} private void Aa2 (InputStream inputstream) {System.out.println ("in");} public static void Aa3 (int num) {System.out.println ("Aa3" +num);}}

2: Reflection of the constructor of this class

//the constructor of the reflection class that creates the object of the class/** The purpose of the structure method of reflection: To create an image of a human being, to instantiate an image as a 1: to load a type Class.forName * 2: To obtain the structure of a function GetConstructor * 3: The method of construction (in practice) newinstance ()*/ Public classDemo1 {//reflection Constructor Public person ()@Test Public voidTest1 ()throwsclassnotfoundexception, SecurityException, Nosuchmethodexception, IllegalArgumentException, Ins Tantiationexception, Illegalaccessexception, invocationtargetexception {//The class is loaded first, and the constructor for the class is obtained (the constructor is intended to create the object), and the object is createdClass C = class.forname ("Com.reflction.person"); Constructor Constructor= C.getconstructor (NULL);//accept mutable arguments, NULL for no argumentsPerson person = (Com.reflction.person) constructor.newinstance (NULL);    System.out.println (Person.name); }    //reflection Constructor Public person (String name)@Test Public voidtest2 () {Try{Class C= Class.forName ("Com.reflction.person"); Constructor Constructor1= C.getconstructor (String.class); Person Person1= (person) constructor1.newinstance ("* * *");        System.out.println (Person1.name); } Catch(Exception e) {}}//Reflection Structure Public number (String Name,int age)@Test Public voidtest3 () {Try{Class C= Class.forName ("Com.reflction.person"); Constructor Constructor3= C.getconstructor (String.class,int.class); Person Person3= (person) constructor3.newinstance ("Jack", 23);        System.out.println (Person3.name); } Catch(Exception e) {}}//Reflection structure function private person (list list)@Test Public voidtest4 () {Try{Class C= Class.forName ("Com.reflction.person"); Constructor Constructor4=c.getdeclaredconstructor (java.util.List.class); //private things are not accessible to outsiders, but reflection can, compellingly openConstructor4.setaccessible (true);//violent reflexesArraylist<string> list=NewArraylist<string>(); List.add ("Name"); List.add ("Age"); Person Person4=(person) constructor4.newinstance (list);        System.out.println (Person4.name); } Catch(Exception e) {} }}

3: Method of Reflection Class

Method of Reflection Type */* The purpose of the method of reflection: To run the method * 1: Load the object Class.forName () * 2: Get the Method Getmethod,getdeclaredmethod () * 3: Run the method Invoke ();            */public class demo2{//reflection type public void AA () @Testpublic void Test1 () {try {human person=new person (); Load Class c = class.forname ("Com.reflction.person");//Obtain Method Method=c.getmethod ("AA", NULL);//The first method, the second one /Let the method Method.invoke (person, null);//Let the elephant run//For example: WC method, who must go to WC, to spread the person to the like} catch (Exception e) {}}//reflect this method public void Aa1 (String name,int age) @Testpublic void Test2 () {try {person person=new person (); Class C = class.forname ("Com.reflction.person"); Method Method=c.getmethod ("Aa1", String.class,int.class); Method.invoke (person, "Jack", 23);} catch (Exception e) {}}//reflect this method private void Aa2 (InputStream inputstream) @Testpublic void Test3 () {try {person person=new P Erson (); Class C = class.forname ("Com.reflction.person"); Method Method=c.getdeclaredmethod ("Aa2", Inputstream.class);//private method.setaccessible (TRUE);//Violence opens, Without this remark, private cannot visit Method.invoke (person, New FileInputStream ("F:\\1.txt"));} catch (Exception e) {}}//reflection public static void Aa3 (int num) @Testpublic void Test4 () throws Exception{person Person=new Perso N (); Class C = class.forname ("Com.reflction.person"); Method Method=c.getmethod ("Aa3", Int.class), Method.invoke (null,23),//static method does not have to be transferred to the image, and of course can also be transferred}}

3: Field of Reflection class

　

Reflection Field/** Reflection field purpose: To get the value of a field, or to block a field's value by * 1: Load class * 2: Fetch field * 3: Gets the value of that field *///public String Npublic class Demo3 {@Testpublic void tes T1 () throws Exception{person person=new person ();//load Class c = class.forname ("Com.reflction.person");//Fetch field fields Field=c.getfield ("name");//Obtain the field of the image, take the value of the field System.out.println (Field.get (person));//You can also set the value of the field field.set (person, "Xiaoli"); System.out.println (person.name);} The Reflection field private int password=123; @Testpublic void Test2 () throws Exception{person person=new person (); Class C = class.forname ("Com.reflction.person"); Field Field=c.getdeclaredfield ("password"); Field.setaccessible (true);//Violence opens PrivateSystem.out.println (Field.get ( person)); Field.set (person, 456); System.out.println (Field.get (person));}}

　　

Java Reflection Classic Summary