java introspection Introspector

Outline:

1. JavaBean specification
2. introspection

A, JavaBean specifications

JavaBean - like subject to the following specifications.

1. Implement java.io.Serializable.
2.  javaBean property is a private member variables have getter / setter methods. It can also be provided only getter methods, such as read-only attribute called attribute; can also be provided only setter methods, such property called write-only property.
3. JavaBean must have an empty constructor
4. JavaBean must have a public constructor

Second, introspection

• First introspective nature is reflective use
• You can quickly get getter and setter javaBean variable by introspection, to quickly operate bean object.

Test javaBean

public class Person {
    private String name ;
    private int age ;
    public void say(){
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

 

1. JavaBean class descriptor can get all the properties and methods of an object by BeanInfo

    public  static  void main (String [] args) throws Exception {
         // Get BeanInfo object that is used to acquire an attribute description javaBean 
        BeanInfo BeanInfo = Introspector.getBeanInfo (the Person. class );
         // The method described is 
        MethodDescriptor [] methodDescriptors = beanInfo.getMethodDescriptors ();
         // attribute descriptor 
        the PropertyDescriptor [] = propertyDescriptors beanInfo.getPropertyDescriptors ();
         // test object 
        the Person Person = new new the Person (); 

        for (the PropertyDescriptor PropertyDescriptor: propertyDescriptors) {
             //属性名
            System.out.println("Person的属性:"+propertyDescriptor.getName());
            if("name".equals(propertyDescriptor.getName())){
                //属性读方法
                Method readMethod = propertyDescriptor.getReadMethod();
                //属性的写方法
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(person,"xiaoming");
                System.out.println("person的name:"+readMethod.invoke(person));
                Class<?> propertyType = propertyDescriptor.getPropertyType();
                System.out.println ("Type property:" + propertyType.getName ()); 
            } 
        } 
    }

 

2. direct access to a property descriptor

    public  static  void main (String [] args) throws Exception { 
        the Person p = new new the Person ();
         // direct access by name descriptor attribute
         // Get the name attribute descriptor facilitate our direct manipulation of the object name property p. 
        Descriptor = the PropertyDescriptor new new the PropertyDescriptor (. "Name", the Person class ); 
        Method, writeMethod = descriptor.getWriteMethod (); 
        writeMethod.invoke (P, "nananan" ); 
        System.out.println ( "Person Object name:" + descriptor. . getReadMethod () Invoke (P)); 
    }