14th. Type Information 1 (reflection of Java)

Reflection of the 1.java language

1  Packagecn.itcast_01;2 /*1. Get the construction method through reflection and use3 *//Get byte-code file Object4 Class C = class.forname ("Cn.itcast_01.Person");5 //Gets the specified constructor object (only acquired)6 The formal parameter of the method is the form parameter of the construction method. Class object (class<?> .... parametertypes)7 * The Parametertypes parameter is an array of Class objects8 Constructor con = c.getdeclaredconstructor (string.class);9 //using the constructor to create an instance object of the classTen //con.setaccessible (true); Canceling language access checks One Object obj = Con.newinstance ("Wind Qing"); A * 2. Get the member method by reflection and use - *//Get byte-code file Object - Class C = class.forname ("Cn.itcast_01.Person"); the Constructor con = c.getconstructor (); - Object obj = con.newinstance (); - //Public Method GetMethod (String name,class<?> .... parametertypes) - The first parameter represents the method name, and the second parameter represents the class type of the method's argument + //Get Member Method Object - Method m1 = C.getmethod ("show"); + method m2 = C.getmethod ("method", String.class); A //Call member methods through this object at M1.invoke (obj);//M1 method that invokes the Obj object - M2.invoke (obj, "hello");//M2 method that invokes the Obj object - * 3. Get member variables by reflection and use - *//Get a single member variable - * Field Addressfield = C.getfield ("address"); - *//Assign a value to the specified variable in * Addressfield.set (obj, "Beijing"); -  *  to *//Cancel language access check + * Addressfield.setaccessible (TRUE); - * Con.setaccessible (TRUE); the * M1.setaccessible (TRUE); *  */ $  Public classReflectdemo {Panax Notoginseng  -}

2. Get the constructor object and use the

1  Packagecn.itcast_01;2 3 ImportJava.lang.reflect.Constructor;4 5  Public classReflectDemo2 {6      Public Static voidMain (string[] args)throwsException {7         //Class public final class Class<t>extends Object8         //gets the byte-code file object for the class9         /*1.static class<?> forname (String className)Ten * 2.public final class<?> getclass () One * 3. For example, the type of String.class is class<string>.  A          */ -          //Get bytecode File object -Class C = class.forname ("Cn.itcast_01.Person"); the         //Get Constructor Method object -          /*1.constructor<t> getconstructor (class<?> ... parametertypes) - gets the public constructor object for the specified parameter - * 2. Constructor<?>[] GetConstructors () + get all public constructor objects - 3. Constructor<t> getdeclaredconstructor (class<?> ... parametertypes) + gets the constructor object for the specified argument A 4.constructor<?>[] getdeclaredconstructors () at get all constructor objects -           */ -         //Get Constructor Object -         //Constructor con = c.getconstructor ();//non-parametric construction -Constructor con = c.getdeclaredconstructor (String.class,int.class); -         //To call a construction method using a constructor object inObject obj = con.newinstance ("Zhang San", 22); -Person P = (person) con.newinstance ("Zhang San", 22); toSystem.out.println (obj);//Person [Name= Zhang San, age=22] +SYSTEM.OUT.PRINTLN (P);//Person [Name= Zhang San, age=22] -     } the}

3. Get the normal member method

1  Packagecn.itcast_01;2 ImportJava.lang.reflect.Constructor;3 ImportJava.lang.reflect.Method;4  Public classReflectDemo3 {5@SuppressWarnings ("Unchecked")6      Public Static voidMain (string[] args)throwsException {7         //gets the byte-code file object for the class8Class C = class.forname ("Cn.itcast_01.Person");9         //Get Constructor ObjectTenConstructor con =c.getdeclaredconstructor (); One         //Create a new instance AObject obj =con.newinstance (); -         /*get a member method object from a bytecode file object: - * 1.Method GetMethod (String name, Class<?> .... parametertypes) the * 2.method[] getmethods () - * 3.Method Getdeclaredmethod (String name, Class<?> .... parametertypes) - * Returns a method object that reflects the specified declared method of the class or interface represented by this class object.  - * 4.method[] getdeclaredmethods () + * Returns an array of method objects, including private and public methods, except for inheritance -          */ +         //method[] m = C.getdeclaredmethods (); A         //gets the member method object (Parameter list: Method name, method parameter of the. Class object) atMethod m1 = C.getdeclaredmethod ("Show"); -         //using member method Objects -M1.invoke (obj);//Show Method -         //Get Member Method Object -Method m2 = C.getdeclaredmethod ("Method", String.class); -         //Use this method inM2.setaccessible (true); -M2.invoke (obj, "Zhang San");//method of Zhang San to System.out.println (M2.getname ()); +     } -}

4. Get Field Properties

1  Packagecn.itcast_01;2 ImportJava.lang.reflect.Constructor;3 ImportJava.lang.reflect.Field;4 5  Public classReflectDemo4 {6      Public Static voidMain (string[] args)throwsException {7         //gets the byte-code file object for the class8Class C = class.forname ("Cn.itcast_01.Person");9         //Get Constructor ObjectTenConstructor con = c.getdeclaredconstructor ();//no parameter constructor One         //Create a new instance of the class (using the parameterless constructor) AObject obj =con.newinstance (); -         //Get Field Object -         /*1.Field Getdeclaredfield (String name) the * 2.field[] getdeclaredfields () - * 3.Field GetField (String name) - * 4.field[] getfields () -          */ +Field NameField = C.getdeclaredfield ("name"); -Field Agefield = C.getdeclaredfield ("Age"); +         //Assigning a value to a Field object (object must be set) ANamefield.setaccessible (true); atAgefield.setaccessible (true); -Namefield.set (obj, "Zhang San"); -Agefield.set (obj, 22); -System.out.println (obj);//Person [Name= Zhang San, age=22] -     } -}

14th. Type Information 1 (reflection of Java)