Java introspection mechanism Introspector

Two ways to access the JavaBean property

1) Call the Bean's Setxxx or getxxx method directly;

2) through introspective technology access (the Java.beans package provides an introspective API), introspective technical access is also available in two ways:

A) The properties of the bean are manipulated through the PropertyDescriptor class;

b) The BeanInfo of the Bean object is obtained through the Introspector class, and then the descriptor (PropertyDescriptor) of the property is obtained through BeanInfo, and the property descriptor is used to obtain a corresponding getter/ Setter methods, and then invoke these methods through the reflection mechanism.

public class person {    private string name;//field    private string password;//field    private Integer age;//field 
    //a Get or set method is added to the field, it is called the property public     String getXxx () {        return "AA";    }    setter/getter}   

The following is an introspective mechanism to manipulate the person object.

Get all the properties of the class

@Test public    void Test1 () throws Exception {        BeanInfo BeanInfo = introspector.getbeaninfo (Person.class  );        propertydescriptor[] PropertyDescriptors = beaninfo.getpropertydescriptors ();//Get the property descriptor        for ( PropertyDescriptor propertydescriptor:propertydescriptors) {            System.out.println (Propertydescriptor.getname ( ));        }    }

Execution Result: Age class money name password xxx

Includes the attribute class inherited from the parent class.

Get all the properties in this class

@Test public    void Test2 () throws Exception {        //rejects the property inherited from Object        BeanInfo BeanInfo =  Introspector.getbeaninfo (Person.class, Object.class);        propertydescriptor[] PropertyDescriptors = beaninfo.getpropertydescriptors ();        For (PropertyDescriptor propertydescriptor:propertydescriptors) {System.out.println ( Propertydescriptor.getname ()); } }

Manipulating a bean's specified properties

@Test public    void Test3 () throws Exception {person person        = new Person ();        PropertyDescriptor PropertyDescriptor = new PropertyDescriptor ("Age", Person.class);        Get the Write method of the attribute, assign a value to the property method        Setagemethod = Propertydescriptor.getwritemethod ();//Setage        Setagemethod.invoke ( Person, a.); Gets the value of the property System.out.println (Person.getage ()); Method Getagemethod = Propertydescriptor.getreadmethod (); System.out.println (Getagemethod.invoke (person, null));}       

Gets the type of the property of the current operation

@Test public    void Test4 () throws Exception {        PropertyDescriptor propertydescriptor = new PropertyDescriptor ("Money", Person.class);                class<?> PropertyType = propertydescriptor.getpropertytype ();        System.out.println (PropertyType);    }   

Java introspection mechanism Introspector