java - 将 ConversionService 注入(inject)自定义转换器

Question

使用 Spring mvc-3。我正在编写一个自定义转换器，它需要访问注册到 ConversionService 的其他转换器。

我怎样才能做到这一点？我尝试将我的自定义转换器编写为:

  class CustomConverter<X, Y>{
     @Autowired ConversionService service;
     //+getter & setters of service

     public Y convert(X input){
          // I need access to service to lookup simple conversions such as
          // String array to Long array etc..

     }

  }

我通过 applicationContext.xml 注册了我的自定义转换器

  <bean id="conversionService" class="org.springframework.context.support.ConversionServiceFactoryBean">
     <property name = "converters">
         <list>
            <bean class="CustomConverter"/>
         </list>
     </property>
  </bean>

但是，spring 拒绝将服务注入(inject)我的 CustomConverter(它始终为空)。我怎样才能做到这一点？

谢谢!

Answer 1

我遇到了同样的问题。有一个issue SPR-6415在 Spring JIRA 中涵盖了这个问题。我已经根据这个问题的讨论在这里给出了我的解决方案。这与@nmervaillie 的回答原理相同，但您不必实现自己的 ConversionServiceFactoryBean。

/**
 * Base class of @{code Converter} that need to use {@code ConversionService}.
 * Instances of implementing classes must be spring-managed to inject ConversionService.
 * 
 * @author Michal Kreuzman
 */
public abstract class CoversionServiceAwareConverter<S, T> implements Converter<S, T> {

  @Inject
  private ConversionService conversionService;

  protected ConversionService conversionService() {
    return conversionService;
  }

  /**
   * Add this converter to {@code ConverterRegistry}.
   */
  @SuppressWarnings("unused")
  @PostConstruct
  private void register() {
    if (conversionService instanceof ConverterRegistry) {
      ((ConverterRegistry) conversionService).addConverter(this);
    } else {
      throw new IllegalStateException("Can't register Converter to ConverterRegistry");
    }
  }
}

@Component
public class SampleConverter extends CoversionServiceAwareConverter<Object, Object> {

    @Override
    public String convert(Object source) {
        ConversionService conversionService = conversionService();

        // Use conversionService and convert
    }
}