JSF列表转换器

Question

如何为JSF2中的A类项目列表编写转换器？我已经为A类编写了一个转换器,但这些项目使用默认的toString()函数显示:"A @ hashcode".

我需要使用转换器而不是支持bean方法,以便进行验证(Hibernate Validator).

更多信息

这就是我使用列表的方式:

<h:inputText id="destinations" value="#{rule.destinations}" converter="gr.panayk.vinyls.Destination"/>

#{rule.destinations}的List<Destination>类型.我期待以逗号分隔的已转换目的地列表.

解

我附上了BalusC提出的List转换器.

@FacesConverter(value="gr.panayk.vinyls.converter.DestinationList")
public class DestinationListConverter implements Converter
{
    @Override
    public Object getAsObject(final FacesContext context, final UIComponent component, final String values)
    {
        final Validator validator = Validation.buildDefaultValidatorFactory().getValidator();

        final List<Destination> result = new ArrayList<Destination>(); 
        for (String value : values.split(",", -1))
        {           
            final String trimmedValue = value.trim();

            final Set<ConstraintViolation<Destination>> violations = validator.validateValue(Destination.class, "data", trimmedValue);
            if (!violations.isEmpty())
            {
                throw new ConverterException(new FacesMessage(violations.iterator().next().getMessage()));
            }

            result.add(new Destination(trimmedValue));
        }       

        final Set<ConstraintViolation<Rule>> violations = validator.validateValue(Rule.class, "destinations", result);
        if (!violations.isEmpty())
        {
            throw new ConverterException(new FacesMessage(violations.iterator().next().getMessage()));
        }       

        return result;
    }

    @Override
    public String getAsString(final FacesContext context, final UIComponent component, final Object value)
    {
        if (value instanceof List<?>)
        {
            final StringBuffer result = new StringBuffer();

            final List<?> list = (List<?>) value;

            for (int i = 0; i < list.size()-1; i++)
            {               
                if (list.get(i) instanceof Destination)
                {
                    result.append(((Destination) list.get(i)).getData());
                    result.append(", ");
                }
                else
                {
                    throw new IllegalArgumentException( "Cannot convert " + value + " object to Destination in DestinationConverter." );
                }
            }

            if (!list.isEmpty())
            {
                if (list.get(list.size()-1) instanceof Destination)
                {
                    result.append(((Destination) list.get(list.size()-1)).getData());
                }
                else
                {
                    throw new IllegalArgumentException( "Cannot convert " + value + " object to Destination in DestinationConverter." );
                }
            }

            return result.toString();
        }
        else
        {
            throw new IllegalArgumentException( "Cannot convert " + value + " object to List in DestinationConverter." );
        }
    }
}

Answer 1

我已经为A类编写了一个转换器,但这些项目使用默认的toString()函数显示:"A @ hashcode".

如果您没有在组件上明确声明转换器,则会发生这种情况.在例如<h:selectManyCheckbox>并<h:selectManyListbox>明确声明转换器是必需的,因为所有的JSF/EL知道是该值的类型List,而不是List<A>(通用类型运行时期间丢失).如果您没有声明转换器,那么这些值将被视为String(因为HTML输出和HTTP请求参数值的默认值).

例如

<h:selectManyCheckbox converter="aConverter">

同

@FacesConverter(value="aConverter", forClass=A.class)
public class AConverter implements Converter {

    // ...

}

当你使用单项输入,比如明确声明上述转换器中是没有必要<h:selectOneMenu>因为forClass无论如何都会匹配.