java - 如果可能的话，是否可以在请求范围内注入(inject)bean，如果它对于线程不活跃，则注入(inject)原型(prototype)？

Question

我想将请求作用域 bean 注入(inject)到单例作用域中。我可以使用Provider来做到这一点。当没有范围请求对线程不活动时，就会出现此问题。在这种情况下，我想将 bean 注入(inject)例如原型(prototype)范围。那可能吗？例如。代码:

public class Tenant {

    private String name;

    ...
}

@Configuration
public class AppConfig {

  @Bean
  @Scope(ConfigurableBeanFactory.SCOPE_REQUEST)
  public Tenant prototypeBean() {
      return new Tenant();
  }

  @Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE)
  public Tenant prototypeBean() {
      return new Tenant();
  }

  @Bean
  public MySingletonBean singletonBean() {
      return new MySingletonBean();
  }

public class MySingletonBean {

  @Autowired
  private Provider<Tenant> beanProvider;
//inject conditionally on request or prototype scope

  public void showMessage() {
      Tenant bean = beanProvider.get();
  }
}

我想避免此消息出现错误:

Error creating bean with name 'tenantDetails': 
Scope 'request' is not active for the current thread; 
consider defining a scoped proxy for this bean if you intend to 
refer to it from a singleton; 
nested exception is java.lang.IllegalStateException: No thread-bound 
request found: Are you referring to request attributes outside of an 
actual web request, or processing a request outside of the originally 
receiving thread? If you are actually operating within a web request 
and still receive this message, your code is probably running outside 
of DispatcherServlet/DispatcherPortlet: In this case, use 
RequestContextListener or RequestContextFilter to expose the current 
request.

Answer 1

如果需要类似的东西，那么应该重新考虑应用程序的设计。

这可能吗？是的。

@Component
@RequestScope
public class RequestScopeTenant implements Tenant {

    private String name;

    ...
}

这样我们就有了请求作用域的 bean。

@Component
@PrototypeScope
public class DefaultTenant implements Tenant {

    private String name;

    ...
}

这里我们有默认的租户。

@Configuration
public class AppConfig {

  @Primary
  @Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE)
  public Tenant prototypeBean(RequestScopeTenant requestScopeTenant, DefaultTenant defaultTenant) {
      return RequestContextHolder.getRequestAttributes() != null ? requestScopeTenant : defaultTenant;
  }

  @Bean
  public MySingletonBean singletonBean() {
      return new MySingletonBean();
  }

这样，当没有可用的请求范围时，将返回默认租户。

再说一次，如果您必须实现类似的东西 - 更改设计或创建自定义范围。