码迷,mamicode.com
首页 > 编程语言 > 详细

Java Reflection API | Java.lang.Class

时间:2016-06-27 12:15:23      阅读:202      评论:0      收藏:0      [点我收藏+]

标签:

ref: http://www.studytonight.com/java/reflection-api

Reflection API

reflection means ability of a software to analyze itself. In java, Reflection API provides facility to analyze and change runtime behavior of a class, at runtime

For Example, using reflection at the runtime you can determine what method or modifiers a class supports

 

What is reflect package ?

java.lang.reflect package encapsulates serveral important interface and classes. These classes and interface define methods which are used for reflection

 

 class            description

----------------------------------------------------------------------------------------------------------

Array            allow you to dynamically created and manipulate arrays

Constructor         gives info abt constructor of a class

Field              provides info abt field

Method            procide info abt method

Modifier           provide info abt class and member access modifier

Proxy             supports dynamic proxy classes

 

java.lang.Class is another important class used in Reflection API

 

 

Uses of Reflection

1. Developing IDE
2. Debugging and Test tools

3. Loading drivers and providing dynamic info

 

Disadvantages of Reflection

1. Low performance

2. Security risk

3. Violation of OOPs concept

 

************************* cut**************************

Reflection Class

 

java.lang.Class 

Class is a final class injava.lang package which extends Object class. Instance of this class 

represents classes and interfaces in a running java application. It is used to analyze and change dynamic behavior of a class at runtime

 

Some Important Methods of java.lang.Class class

This class defines several methods using which we can get info about methods, constructors, modifiers and members of a class at runtime

forName()    

1. this method takes fully qualified name of classes or nterfaces as its argument and return instance 

   of the class associated with it. 

2. static Class<?> forName(String className)

class Student{}
class Test
{
 public static void main(String args[])
 {
  Class c = Class.forName("Student");
  System.out.println(c.getName());
 }
}
output: Student


getConstructors() and getDeclaredConstructors()

1. getConstructors() returns array of Constructors object that represent all the public constructors of the invoking object. This method only returns public constructor. getDeclaredConstructors() will return all constructors

Constructor< ?>[] getConstructors();
Constructor< ?>[] getDeclaredConstructors();

Example using getConstructors() and getDeclaredConstructors() method

Class c = Class.forName("Student");
  Constructor< Student>[] ct = c.getConstructors();
  for(int i=0; i< ct.length; i++)
    { System.out.println(ct[i]); }
  Constructor< Student>[] cdt = c.getDeclaredConstructors();
  for(int i=0;i< cdt.length;i++)
    { System.out.println(cdt[i]);}

output:
  public Student()
  public Student()
  Student(java.lang.String)

getMethods() and getDeclaredMethods()

getFields() and getDeclaredFields()

Example using getFields() and getDeclaredFields() method

 




 

Java Reflection API | Java.lang.Class

标签:

原文地址:http://www.cnblogs.com/morningdew/p/5619385.html

(0)
(0)
   
举报
评论 一句话评论(0
登录后才能评论!
© 2014 mamicode.com 版权所有  联系我们:gaon5@hotmail.com
迷上了代码!