Spring和@Value注释

Question

我试图用Spring框架构建一个控制台应用程序。

我有一个由@springbootapplication注释的类：

@SpringBootApplication
public class LoaderApplication {

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

和由@component注释的类

@Component
public class ElasticLoader implements CommandLineRunner {

    // Elastic properties
    @Value("${elasticTransportAddress:#{null}}")
    private String elasticTransportAddress;

    private static final Logger log = LoggerFactory.getLogger(ElasticLoader.class);

    @Override
    public void run(String... arg) throws Exception {
        if (!( elasticTransportAddress != null && elasticTransportAddress.isEmpty() )) {
            log.error("[elasticTransportAddress] is not defined in property file");
            return;
        }
        log.info("-> ElasticLoader.run");
    }
}

    <beans profile="companies">
    <!-- allows for ${} replacement in the spring xml configuration from the
        application-default.properties, application-dev files on the classpath -->
    <context:property-placeholder
            location="classpath:companies.properties"
            ignore-unresolvable="true" />

    <!-- scans for annotated classes in the com.env.dev package -->
    <context:component-scan base-package="ru.alexeyzhulin" />
</beans>

2017-01-15 00:10:39.697  INFO 10120 --- [           main] ru.alexeyzhulin.LoaderApplication        : The following profiles are active: companies

但是，当我在application.properties中定义属性并使用默认配置文件时，属性ElasticTransportAddress将被分配。

Answer 1

if条件中出现错误。这：

if (!( elasticTransportAddress != null && elasticTransportAddress.isEmpty() ))

相当于这个：

if (elasticTransportAddress == null || !elasticTransportAddress.isEmpty())

因此，在两种情况下会得到错误日志消息+返回：

null

if (elasticTransportAddress == null || elasticTransportAddress.isEmpty())

@Configuration
@Profile("companies")
@PropertySource("classpath:companies.properties")
public final class LoaderApplication {
}