加载构造函数时值为null

Question

Properties我没有在构造函数内部使用，而是看到@Value注解可以解决问题。

它可以在我拥有的另一个实现中工作，但在这里没有

控制器：

@Autowired
private Customer customer;

我的课

@Service
public class Customer {

    /** The soap GW endpoint. */
    @Value("${soapGWEndpoint}")
    private String soapGWEndpoint;

    /** The soap GW app name. */
    @Value("${soapGWApplName}")
    private String soapGWAppName;

    /** The soap GW user. */
    @Value("${generic.user}")
    private String soapGWUser;

    /** The soap GW password. */
    @Value("${generic.user.password}")
    private String soapGWPassword;

    public Customer () {
        // All parameters are null:
        login(soapGWEndpoint, soapGWAppName, soapGWUser, soapGWPassword);
    }
}

但是它们位于application.properties文件中。

为什么在这种情况下我不能使用@Value？

Answer 1

另一种选择是像这样使用构造函数注入

@Service
public class Customer {

  private String soapGWEndpoint;
  private String soapGWAppName;
  private String soapGWUser;
  private String soapGWPassword;

  @Autowired
  public Customer(@Value("${soapGWEndpoint}") String soapGWEndpoint,
                @Value("${soapGWApplName}") String soapGWAppName,
                @Value("${generic.user}") String soapGWUser,
                @Value("${generic.user.password}") String soapGWPassword) {
    this.soapGWEndpoint = soapGWEndpoint;
    this.soapGWAppName = soapGWAppName;
    this.soapGWUser = soapGWUser;
    this.soapGWPassword = soapGWPassword;
    login(soapGWEndpoint, soapGWAppName, soapGWUser, soapGWPassword);
  }
}

Answer 2

在对象完全实例化之前，Spring不会注入预操作对象的值（Spring要做的第一件事是调用构造函数，因为它是创建新对象的默认方式）。您应该在@PostConstruct方法中调用login（），以便Spring在初始化对象后自动调用它：

@Service
public class Customer {

    /** The soap GW endpoint. */
    @Value("${soapGWEndpoint}")
    private String soapGWEndpoint;

    /** The soap GW app name. */
    @Value("${soapGWApplName}")
    private String soapGWAppName;

    /** The soap GW user. */
    @Value("${generic.user}")
    private String soapGWUser;

    /** The soap GW password. */
    @Value("${generic.user.password}")
    private String soapGWPassword;

    public Customer () {
    }

    @PostConstruct
    public void init() {
      login(soapGWEndpoint, soapGWAppName, soapGWUser, soapGWPassword);
    }
}