SPRING IN ACTION 第4版笔记-第一章-004-用类来管理DI

一、

1.

 package chapter01.sia.knights.config;

 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;

 import chapter01.sia.knights.BraveKnight;
 import chapter01.sia.knights.Knight;
 import chapter01.sia.knights.Quest;
 import chapter01.sia.knights.SlayDragonQuest;

 @Configuration
 public class KnightConfig {

   @Bean
   public Knight knight() {
     return new BraveKnight(quest());
   }

   @Bean
   public Quest quest() {
     return new SlayDragonQuest(System.out);
   }

 }

解析：

(1)public Knight knight() {

return new BraveKnight(quest());
}　　说明new knight时用BraveKnight

(2)@Bean

public Quest quest() {
return new SlayDragonQuest(System.out);
}　　说明new quest时用SlayDragonQuest

 package chapter01.sia.knights;

 import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;

 public class KnightMain {

   public static void main(String[] args) throws Exception {
     //ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath:knight.xml");
     //ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath:minstrel.xml");
     ApplicationContext context = new AnnotationConfigApplicationContext(
             chapter01.sia.knights.config.KnightConfig.class);
     Knight knight = context.getBean(Knight.class);
     knight.embarkOnQuest();
     //context.close();
   }

 }

运行

Embarking on quest to slay the dragon!