spring中注册bean(通过代码动态注册)

看公司的源代码，在一个类中使用到了BeanDefinitionBuilder这个类，在学习之后才知道在项目中可能没有注册bean，在使用的时候才会进行注册，就涉及到了动态bean的注册，所以，在文章中会整理一下关于这方面的知识。

2017.12.22，这篇文档还有些难，下次复习时再研究一下这篇文档：https://www.cnblogs.com/hanjiehu/p/5978260.html

一：概述

1.目录

　　

2.知识点

　　Spring 2.0 增加了 BeanDefinitionBuilder ，通过 BeanDefinitionBuilder 可以动态的创建一个Applicatoin Context 而不需要使用XML。

　　

二：程序

1.User.java

 package cn.caojun.spring;

 public class User {
     private String username;
     private String password;

     public String getUsername() {
         return username;
     }

     public void setUsername(String username) {
         this.username = username;
     }

     public String getPassword() {
         return password;
     }

     public void setPassword(String password) {
         this.password = password;
     }

     @Override
     public String toString() {
         return "User{" +
                 "username='" + username + '\'' +
                 ", password='" + password + '\'' +
                 '}';
     }
 }

2.UserService

 package cn.caojun.spring;

 public class UserService {
     private User user;

     public void test(){
         System.out.println(user.getUsername()+"--------------------");
     }

     public User getUser() {
         return user;
     }

     public void setUser(User user) {
         this.user = user;
     }
 }

3.applicationContext.xml

 <?xml version="1.0" encoding="UTF-8"?>
 <beans xmlns="http://www.springframework.org/schema/beans"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
     <bean id="SpringDemo" class="cn.caojun.spring.SpringDemo"></bean>
 </beans>

4.SpringDemo.java

 package cn.caojun.spring;

 import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryAware;
 import org.springframework.beans.factory.support.BeanDefinitionBuilder;
 import org.springframework.beans.factory.support.DefaultListableBeanFactory;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationListener;
 import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.event.ContextRefreshedEvent;
 import org.springframework.context.support.ClassPathXmlApplicationContext;

 public class SpringDemo implements BeanFactoryAware, ApplicationListener<ContextRefreshedEvent> {

     private DefaultListableBeanFactory beanFactory;

     /**
      * 主函数
      * @param args
      */
     public static void main(String[] args) {
         ApplicationContext applicationContext = new ClassPathXmlApplicationContext("classpath:spring/applicationContext.xml");
         ////将applicationContext转换为ConfigurableApplicationContext
         ConfigurableApplicationContext configurableApplicationContext = (ConfigurableApplicationContext) applicationContext;
         //// 获取bean工厂并转换为DefaultListableBeanFactory
         DefaultListableBeanFactory defaultListableBeanFactory = (DefaultListableBeanFactory) configurableApplicationContext.getBeanFactory();
         System.out.println("ContextRefreshed**");
         //获取bean
         User user=(User) defaultListableBeanFactory.getBean("user");
         String userName=user.getUsername();
         String password=user.getPassword();
         System.out.println("userName="+userName+","+"password="+password);
     }

     /**
      *BeanFactory转换为DefaultListableBeanFactory
      * @param beanFactory
      * @throws BeansException
      */
     public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
         System.out.println("setBeanFactory==");
         this.beanFactory = (DefaultListableBeanFactory) beanFactory;
     }

     /**
      *
      * @param contextRefreshedEvent
      */
     public void onApplicationEvent(ContextRefreshedEvent contextRefreshedEvent) {
         System.out.println("ContextRefreshed--");
         BeanDefinitionBuilder userBeanDefinitionBuilder = BeanDefinitionBuilder.genericBeanDefinition(User.class);
         userBeanDefinitionBuilder.addPropertyValue("username", "chinfeng");
         userBeanDefinitionBuilder.addPropertyValue("password", "123456");
         beanFactory.registerBeanDefinition("user", userBeanDefinitionBuilder.getRawBeanDefinition());
         System.out.println("ContextRefreshed++");
         BeanDefinitionBuilder usersBeanDefinitionBuilder = BeanDefinitionBuilder.genericBeanDefinition(UserService.class);
         usersBeanDefinitionBuilder.addPropertyReference("user", "user");
         //beanFactory.registerBeanDefinition("userService", usersBeanDefinitionBuilder.getRawBeanDefinition());
     }
 }

5.效果