Spring <idref>与<ref>的区别
Spring中,<idref>和<ref>还是比较容易混淆的。。 他们的本质区别是<idref>对应的是id的值，对应该值的property一般来说是String类型， 而<idref>对应的是bean的值， 对应该值的property是bean的类型。 这样说还是比较模糊的，看下面的例子。

package Impl;public class Teacher {public Teacher(){}public Teacher(String name,Student student){}}

package Impl;public class Student {private Teacher teacher;  //Teacher类型//private IPhone phone;private String teacherId;  //String类型public Student(){}public Student(Teacher teacher){this.teacher = teacher;}public Teacher getTeacher() {return teacher;}public void setTeacher(Teacher teacher) {this.teacher = teacher;}public String getTeacherId() {return teacherId;}public void setTeacherId(String teacherId) {this.teacherId = teacherId;}}

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:p = "http://www.springframework.org/schema/p"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd"><bean id="student" ><property name="teacher"><ref bean="teacher"/></property><property name="teacherId"><idref bean="teacher"/></property></bean><bean id="teacher" type="java.lang.String"><value>Morgan</value></constructor-arg><constructor-arg index="1" ref="student"></constructor-arg></bean></beans>

package test;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;import Impl.Student;public class TestConstructorBeans {public static void main(String args[]){ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");//context.getBean("teacher");ApplicationContext context2 = new ClassPathXmlApplicationContext(new String[]{"constructorBeans.xml"},context);//context.getBean("phone2");    Student s = (Student)context2.getBean("student");    System.out.println(s.getTeacherId());}}

需要指出的是，<idref bean="teacher"/> 可以用<value>teacher</value>替代，但是Spring是不会检出value是否存在的。。而是用idref， sping在加载的时候会检出idref的值是否存在。 因为拿到另一个bean的id， 基本上都是想在运行时通过getBean得到bean的实例。