Introspector(内省)简单演示样例 与 简单应用

简单演示样例：

package com.asdfLeftHand.test;

import java.beans.BeanDescriptor;
import java.beans.BeanInfo;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.MethodDescriptor;
import java.beans.PropertyDescriptor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

class Person {

	private String name;
	private int age;

	public int getAge() {
		return age;
	}

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

	public String getName() {
		return name;
	}

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

}

public class IntrospectorTest {

	/**
	 * @param args
	 * @throws IntrospectionException
	 * @throws InvocationTargetException 
	 * @throws IllegalArgumentException 
	 * @throws IllegalAccessException 
	 */
	public static void main(String[] args) throws IntrospectionException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
		// 
		Person person = new Person();
		person.setAge(22);
		person.setName("小强");
		
		BeanInfo beanInfo = Introspector.getBeanInfo(person.getClass());
		//BeanInfo beanInfo = Introspector.getBeanInfo(Person.class);

		System.out.println("--------BeanDescriptor--------");
		BeanDescriptor beanDesc = beanInfo.getBeanDescriptor();
		Class cls = beanDesc.getBeanClass();
		System.out.println(cls.getName());

		System.out.println("--------MethodDescriptor-------");
		MethodDescriptor[] methodDescs = beanInfo.getMethodDescriptors();
		for (int i = 0; i < methodDescs.length; i++) {
			Method method = methodDescs[i].getMethod();
			System.out.println(method.getName());
		}
		
		System.out.println("--------PropertyDescriptor------");
		
		PropertyDescriptor[] propDescs = beanInfo.getPropertyDescriptors();
		for(int i = 0; i < propDescs.length; i++) {
			Method methodR = propDescs[i].getReadMethod();
			if (methodR != null) {
				System.out.println("读方法："+methodR.getName());
				Object o= methodR.invoke(person);
				System.out.println(methodR.getName()+":"+o);
			}
			Method methodW = propDescs[i].getWriteMethod();
			if (methodW != null) {
				System.out.println("写方法："+methodW.getName());
				if(methodW.getName().equals("setName")){
					methodW.invoke(person,"小王");
					System.out.println("调用"+methodW.getName()+"方法后的值为："+person.getName());//此处为了方便就直接用person.getName()方法了
				}
			}
		}
	}

}

--------BeanDescriptor--------
com.asdfLeftHand.test.Person
--------MethodDescriptor-------
hashCode
wait
setAge
notifyAll
equals
wait
wait
toString
setName
getAge
notify
getClass
getName
--------PropertyDescriptor------
读方法：getAge
getAge:22
写方法：setAge
读方法：getClass
getClass:class com.asdfLeftHand.test.Person
读方法：getName
getName:小强
写方法：setName
调用setName方法后的值为：小王

一个简单应用：利用内省简化一系列类似的方法为一个通用的方法。

部分代码：

用到common BeanUtils包。

/**
	 * 有一张图片Image表，存有何种对象相应的图像（如 用户头像），用hql语句查处相应的图片集合，
	 * 各种对象字段有差别可是查询方法相似，就写一个通用的方法（相对通用）
	 * 得到某个对象集合的图片。
	 * key:guid+id,value:address+fileName
	 * @param list
	 * @param type 
	 * @return
	 */
	public  Map<String,String> getImagesMap(List<?> list,int imageType) {
		Map<String, String> imagesMap = new HashMap<String, String>();
		List<?> entityList = list;
		for(int i=0;i<entityList.size();i++){ 
			Object entity = entityList.get(i);
			String id = "";
			String guid = "";
			try {
				BeanInfo bi = Introspector.getBeanInfo(entity.getClass(), Object.class);
				PropertyDescriptor[] props = bi.getPropertyDescriptors();
		        for (int i2 = 0; i2 < props.length; i2++) {
		        	String str = props[i2].getName();
		        	if(str.equals("guid")){
		        		guid = BeanUtils.getProperty(entity, str);
		        	}else if(str.endsWith("ID")){
		        		id = BeanUtils.getProperty(entity, str);
		        	}
		        }
			} catch (Exception e) {
				e.printStackTrace();
			}
	        String hql2 = "from Image where guid='"+guid+"' and FKID='"+id+"' and type="+imageType";
			List<Image> list2 = imageDao.query(hql2);
			//,,,
		}
		return imagesMap;
		
	}