Spring自动连接自动连接bean中的属性

Question

我是Spring的新手。我正面临Spring-Boot的问题。我正在尝试将外部配置文件中的字段自动装配到自动装配的bean中。我有以下类

应用程序。Java语言

public class App {

@Autowired
private Service service;

public static void main(String[] args) {

    final SpringApplication app = new SpringApplication(App.class);
    //app.setShowBanner(false);
    app.run();
}

@PostConstruct
public void foo() {
    System.out.println("Instantiated service name = " + service.serviceName);
}
}

AppConfig。Java语言

@Configuration
@ConfigurationProperties
public class AppConfig {

@Bean
public Service service()    {
    return new Service1();
}
}

服务接口

public interface Service {
    public String serviceName ="";
    public void getHistory(int days , Location location );
    public void getForecast(int days , Location location );
}

服务1

@Configurable
@ConfigurationProperties
public class Service1 implements Service {

@Autowired
@Value("${serviceName}") 
public String serviceName;
//Available in external configuration file.
//This autowiring is not reflected in the main method of the application.



public void getHistory(int days , Location location)
{
    //history code
}

public void getForecast(int days , Location location )
{
    //forecast code
}
}

我无法在App类的postconstruct方法中显示服务名称变量。我这样做对吗？

Answer 1

考虑到你的类App注释有@SpringBootApplication和App类在顶部包中，你可以把你的serviceName放在application.properties中，并使用@Value（"${serviceName}"）注入它。不要在类上使用@Component如果您已经在配置上使用@Bean，它会发生冲突，因此@Autowire与@Value

有关更多信息，请参阅文档

你会以这样的结尾

@Service // @Component specialization
public class Service1 implements Service {

@Value("${serviceName}") 
public String serviceName;
//Available in external configuration file.
//This autowiring is not reflected in the main method of the application.



public void getHistory(int days , Location location)
{
    //history code
}

public void getForecast(int days , Location location )
{
    //forecast code
}
}

当您有@组件/@服务/@存储库时，不需要@Bean声明

@Configuration
public class AppConfig {  //other stuff here not duplicated beans  }

还有你的主课

    package com.app;

    @SpringBootApplication // contains @EnableAutoConfiguration @ComponentScan @Configuration   
    public class App {

    @Autowired
    private Service service;

    public static void main(String[] args) {

        final SpringApplication app = new SpringApplication(App.class);
        //app.setShowBanner(false);
        app.run();
    }

    @PostConstruct
    public void foo() {
        System.out.println("Instantiated service name = " + service.serviceName);
    }
    }

Answer 2

您可以通过不同的方式加载属性：

想象一下下面的application.properties，它是由spry-boot自动加载的。

spring.app.serviceName=Boot demo
spring.app.version=1.0.0

>

使用@Value注入值

@Service
public class ServiceImpl implements Service {

@Value("${spring.app.serviceName}") 
public String serviceName;

}

使用@ConfigurationProperties注入值

@ConfigurationProperties(prefix="spring.app")
public class ApplicationProperties {

   private String serviceName;

   private String version;

   //setters and getters
}

您可以使用Autowired从另一个类访问此属性

@Service
public class ServiceImpl implements Service {

@Autowired
public ApplicationProperties applicationProperties;

}

正如您所注意到的，前缀将是spring。app然后spring boot将属性前缀与之匹配，并查找服务名称和版本，然后将注入值。