Springboot组件返回属性值为空

Question

@Component
public class ConnectionService {
    @Value("${spring.datasource.url}")
    private String url;
    @Value("${spring.datasource.username}")
    private String username;
    @Value("${spring.datasource.password}")
    private String password;
    @Value("{spring.liquibase.change-log}")
    private String changelog;

    public ConnectionService() {

    }

    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getChangelog() {
        return changelog;
    }

    public void setChangelog(String changelog) {
        this.changelog = changelog;
    }
}

  @SpringBootApplication
public class MigrationsApplication {
    private static final Logger logger = LoggerFactory.getLogger(MigrationsApplication.class);
    @Autowired
    static
    ConnectionService cs;
    public static void main(String[] args) throws DatabaseException {
          try{
                    cs=new ConnectionService();
                    String dbUrl=cs.getUrl();
                    logger.info("URL:"+dbUrl);
                    String dbUsername=cs.getUsername();
                    logger.info("USERNAME:"+dbUsername);
                    String dbPassword=cs.getPassword();
                    logger.info("PASSWORD:"+dbPassword);
                    String changelogPath=cs.getChangelog();
    }

我做错了什么？我需要组件的完整构造函数吗？这是因为cs是静态的？springboot不是要自动填充这些值吗？

Answer 1

component表示这是一个bean，因此Spring将处理它的生命周期。当bean被创建时，它将用请求的数据填充它。但是，您尝试用它填充静态值，这不是生命周期的一部分。在类中添加一个完整的arg构造函数，并让Spring将其注入到您想要使用它的地方，它就会很好地工作。

编辑：

我刚刚意识到您没有使用静态变量，所以当您适当地让Spring初始化bean时，字段注入应该可以工作

@SpringBootApplication
public class MigrationsApplication.class implements CommandLineRunner {

    private static final Logger logger = LoggerFactory.getLogger(MigrationsApplication.class);
    
    @Autowired
    ConnectionService cs;

    public static void main(String[] args) {
        SpringApplication.run(MigrationsApplication.class, args);
    }
 
    @Override
    public void run(String... args) {
        String dbUrl=cs.getUrl();
        logger.info("URL:"+dbUrl);
        String dbUsername=cs.getUsername();
        logger.info("USERNAME:"+dbUsername);
        String dbPassword=cs.getPassword();
        logger.info("PASSWORD:"+dbPassword);
        String changelogPath=cs.getChangelog();
    }
}