Java reflection mechanism [field reflection]

Java reflection mechanism [field reflection]

1. Reflection Concept and function

Reflection is the mapping of the various components in the Java class into the corresponding Java classes. For example, a Java class is represented by an object of class. The components of a class are divided into member variables, methods, construction methods, packages, and so on.

The Java Reflection mechanism provides the following functions: To judge the class that any object belongs to at run time, to construct an object of any class at run time, to judge the member variables and methods that any class has at run time, to invoke the method of any object at run time, and to generate a dynamic proxy.

2. Field Reflection

The following code replaces the character containing I in the value of type string in the Obj object with ABC. This simple case is a preliminary analysis of the Java reflection mechanism.

Java Code

/* * System abbrev: * System Name: * Component No: * Component Name: * File Name:ReflectTestMain.java * author:qiuzhenping * date:2014-10-25 * Description: <description> */ /* Updation record 1: * Updation date:2014-10-25 * updator:qiuzhenping * Trace No: <trace no> * updation No: <updation no> * Updation Content: <list All contents of updation and all methods updated.> */ Package com.qiuzhping.reflect.main; Import Java.lang.reflect.Constructor; Import Java.lang.reflect.Field; Import Java.lang.reflect.Method; /** * <description functions in a word> * Reflection is the mapping of the various components in the Java class into the corresponding Java classes. * <detail description> * * @author qiuzhenping * @version [version NO, 2014-10-25] * @see [related classes/methods] * @since [Product/module version] */ public class Reflecttestmain { /** <default constructor> */ Public Reflecttestmain () { TODO auto-generated Constructor stub } /** <description functions in a word> * 2014-10-25 * <detail description> * @author qiuzhenping * @param args [Parameters description] * @return void [return type description] * @exception throws [Exception] [exception description] * @see [Related classes#related methods#related properties] */ public static void Main (string[] args) throws exception{ TODO auto-generated Method Stub constructor[] Contructor = Person.class.getConstructors (); Method[] method = Person.class.getMethods (); Person p = new person ("qiuzhping", "100001", "qiuzhping"); field [] field = P.getclass (). Getdeclaredfields (); for (Field F:field) { F.setaccessible (TRUE); System.out.println (F.getname ()); Object obj = F.get (p); System.out.println (obj); //               } Changestringvalue (P); System.out.println (P.tostring ()); } /** <description functions in a word> * Replace the character of type string in the Obj object with the characters in value containing I in abc<br> * 2014-10-26 * <detail description> * @author qiuzhenping * @param obj [Parameters description] * @return void [return type description] * @exception throws [Exception] [exception description] * @see [Related classes#related methods#related properties] */ private static void Changestringvalue (Object obj) throws Exception { field[] fields = Obj.getclass (). Getdeclaredfields (); for (Field f:fields) { F.setaccessible (TRUE);//Violent reflexes if (f.gettype () = = String.class) {//byte-code comparison is used = = String oldValue = (string) f.get (obj); String newvalue = Oldvalue.replaceall ("i", "abc");//Replace All I with ABC F.set (obj, newvalue); } } } Static class Person { public person (int age, string name, string ID, string pwd) { Super (); This.age = age; THIS.name = name; This.id = ID; This.pwd = pwd; } @Override Public String toString () { Return "age =" +age + "\tname =" +name+ "\tid =" +id+ "\tpwd =" +PWD; } private int age; private String name; Private String ID; Private String pwd; public int getage () { return age; } public void Setage (int.) { This.age = age; } Public String GetName () { return name; } public void SetName (String name) { THIS.name = name; } Public String getId () { return ID; } public void SetId (String id) { This.id = ID; } Public String getpwd () { return pwd; } public void SetPwd (String pwd) { This.pwd = pwd; } /** <default constructor> */ Public person () { TODO auto-generated Constructor stub } } }

Java reflection mechanism [field reflection]