Spring Boot如何动态创建Bean示例代码

package com.spring.configuration;  import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.support.BeanDefinitionBuilder; import org.springframework.beans.factory.support.DefaultListableBeanFactory; import org.springframework.boot.autoconfigure.condition.ConditionalOnExpression; import org.springframework.context.ApplicationContext; import org.springframework.context.ConfigurableApplicationContext; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.jdbc.core.JdbcTemplate;  @Configuration /**  * 这里的conditional是一个可选条件，表示当这个表达式为true的时候，才动态创建bean  */ @ConditionalOnExpression("${my.configuration.enabled}") public class DynamicConfiguration {  @Autowired  private ApplicationContext applicationContext;    /**   * 这个方法返回Runnable只是一个幌子，最重要的是执行方法里面的代码   */  @Bean  public Runnable dynamicConfiguration() throws Exception  {   ConfigurableApplicationContext context = (ConfigurableApplicationContext)applicationContext;   DefaultListableBeanFactory beanFactory = (DefaultListableBeanFactory)context.getBeanFactory();      BeanDefinitionBuilder beanDefinitionBuilder = BeanDefinitionBuilder.rootBeanDefinition(UserService.class);   /**    * 设置属性    */   beanDefinitionBuilder.addPropertyValue("name", "myConfigure");   beanDefinitionBuilder.addPropertyValue("jdbcTemplate", applicationContext.getBean(JdbcTemplate.class));      /**    * 注册到spring容器中    */   beanFactory.registerBeanDefinition("userService", beanDefinitionBuilder.getBeanDefinition());   return null;  } } class UserService {  private String name;  private JdbcTemplate jdbcTemplate;  public String getName()  {   return name;  }  public void setName(String name)  {   this.name = name;  }  public JdbcTemplate getJdbcTemplate()  {   return jdbcTemplate;  }  public void setJdbcTemplate(JdbcTemplate jdbcTemplate)  {   this.jdbcTemplate = jdbcTemplate;  } } 

applicationContext.getBean(UserService.class);applicationContext.getBean("userService", UserService.class)