在春靴里找回豆子？

Question

我以前和legacy Spring合作过。我们通过xml配置定义了bean，并手动连接它们。我的团队最终做出了一致的努力来更新注释，并使用Spring Boot而不是Spring MVC的‘传统’方法。

package com.ots;


import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;
import org.springframework.stereotype.Service;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
public class GriefUIApplication{

    public static void main(String[] args) {
        SpringApplication.run(GriefUIApplication.class, args);

        SessionFactory factory = new Configuration().configure("hibernate.cfg.xml")
                .addAnnotatedClass(GriefRecord.class).addAnnotatedClass(RecordId.class)
                .addAnnotatedClass(CrossReferenceRecord.class)
                .buildSessionFactory();

        Statics.setSessionFactory(factory);

        TennisCoach tCoach = new TennisCoach();
        tCoach.getCoach();

    }

}



interface Coach{
    public String workout();
}


@Service
class TennisCoach implements Coach{

    private Coach soccerCoach;
    @Autowired
    private ApplicationContext context;


    public TennisCoach() {

    }

    public Coach getCoach() {

        System.out.println(context + " IS THE VALUE OF THE CONTEXT OBJECT");

        soccerCoach = (SoccerCoach)context.getBean("soccerCoach");

        System.out.println(soccerCoach.getClass());

        return soccerCoach;

    }

    @Override
    public String workout() {
        String practice = "practice your backhand!";
        System.out.println(practice);
        return practice;
    }


}

@Service
class SoccerCoach implements Coach{

    public SoccerCoach() {

    }

    @Override
    public String workout() {
        String practice = "practice your footwork!";
        System.out.println(practice);
        return practice;
    }

}

@RestController
class MyController{

    @GetMapping("/")
    public String sayHello() {

        return "Time on server is: " + new java.util.Date();
    }

}

Answer 1

最常见的方法是使用@autowired注释。另外，因为您有coach接口的两个不同实现，所以您应该使用@qualifier注释来告诉Spring要注入哪个接口实现。

关于这两个注释的一些教程，让您开始：

• https://www.baeldung.com/spring-autowire
• https://www.baeldung.com/spring-qualifier-annotation

对于您的示例，要将bean注入到您的控制器中，您应该执行以下操作：

@RestController
class MyController {

    @Autowired
    @Qualifier("soccerCoach")
    private Coach coach;

    @GetMapping("/")
    public String sayHello() {
        // this should invoke the workout() from SoccerCoach implementation
        System.out.println(coach.workout());

        return "Time on server is: " + new java.util.Date();
    }

}

或者，按照您的意图，使用构造函数注入将SoccerCoach注入到TennisCoach中，代码将变成：

@Service
class TennisCoach implements Coach {

    private Coach soccerCoach;

    @Autowired
    public TennisCoach(@Qualifier("soccerCoach") Coach soccerCoach) {
        this.soccerCoach = soccerCoach;
    }

    public Coach getCoach() {
        System.out.println(soccerCoach.getClass());

        return soccerCoach;
    }

}

@Component
public class AnyComponent {

    @Autowired
    private ApplicationContext applicationContext;

    public void invokeCoach() {
        System.out.println(applicationContext.getBean("tennisCoach"));
        System.out.println(applicationContext.getBean(SoccerCoach.class));
    }

}

@RestController
class MyController {

    @Autowired
    private AnyComponent anyComponent;

    @GetMapping("/")
    public String sayHello() {
        anyComponent.invokeCoach();

        return "Time on server is: " + new java.util.Date();
    }

}

网址：https://www.baeldung.com/spring-autowire：

从Spring2.5开始，框架引入了一种由@Autowired注释驱动的新样式的依赖注入。这个注释允许Spring解析协作bean并将其注入到bean中。