spring依赖注入原理与用法实例分析

package com.wisely.highlight_spring4.ch1.di;
import org.springframework.stereotype.Service;
//使用@Service注解声明当前FunctionService类是Spring管理的一个Bean。
//使用@Component、@Service、@Respository、@Controller是等效的，可
//根据需要选择
@Service
public class FunctionService {
  public String sayHello(String word){
    return "Hello " + word +" !";
  }
}

package com.wisely.highlight_spring4.ch1.di;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service //使用@Service注解声明当前UseFunctionService类是Spring管理的一个Bean
public class UseFunctionService {
  //使用@Autowired 将FunctionService的实体Bean注入到UseFunctionService中
  //让UseFunctionService具备FunctionService的功能，此处使用JSR-330的Inject
  //注解或者JSR-250的@Resource注解等效
  @Autowired
  FunctionService functionService;
  public String SayHello(String word){
    return functionService.sayHello(word);
  }
}

package com.wisely.highlight_spring4.ch1.di;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
@Configuration //@Configuration声明当前类是一个配置类。
//使用@ComponentScan，自动扫描包下所有@Component、@Service、@Respository、@Controller
//的类，并注册为Bean
@ComponentScan("com.wisely.highlight_spring4.ch1.di")
public class DiConfig {
}

package com.wisely.highlight_spring4.ch1.di;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
public class Main {
  public static void main(String[] args) {
     //使用AnnotationConfigApplicationContext作为Spring容器，接收
     //一个配置类作为参数
     AnnotationConfigApplicationContext context =
          new AnnotationConfigApplicationContext(DiConfig.class);
     //获得声明配置UseFunctionService的Bean
     UseFunctionService useFunctionService = context.getBean(UseFunctionService.class);
     System.out.println(useFunctionService.SayHello("world"));
     context.close();
  }
}