将ConversionService注入自定义Converter

Question

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

我怎么能做到这一点？我尝试将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拒绝将服务注入我的CustomConverter(它总是为null).我怎么能做到这一点？

谢谢!

Answer 1

我遇到过同样的问题.Spring JIRA中存在SPR-6415问题,涵盖了这个问题.我根据本期的讨论给出了我的解决方案.它与@nmervaillie的答案相同,但你不必实现自己的原则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
    }
}

Answer 2

我最近用过这样的东西来解决这个问题.使用自定义工厂:

public class MyConversionServiceFactoryBean extends ConversionServiceFactoryBean {

    @Override
    public void afterPropertiesSet() {
        super.afterPropertiesSet();
        ConversionService conversionService = getObject();
        ConverterRegistry registry = (ConverterRegistry) conversionService;
        // register converters that need a nested conversion service
        registry.addConverter(new MyCustomConverter(conversionService));
    }
}

这是这样声明的:

<bean id="conversionService"
    class="com.company.MyConversionServiceFactoryBean">
    <property name="converters">
        <list>
            ... declare standard converters here ...
        </list>
    </property>
</bean>