动态 JSF 转换器

Question

我的 JSF 应用程序背后的数据访问层使用两种不同的日期字段格式（有时是 ddmmyyyy，有时是 yyyymmdd）；显示的日期始终为 dd/mm/yyyy。

有没有办法为单个字段使用两个不同的转换器并动态决定使用哪一个？就像“如果单击此命令按钮，则使用此转换器，否则如果单击此其他命令按钮，请使用该转换器”。

Answer 1

BalusC 在这里解释了为什么这很困难：https://stackoverflow.com/a/7123153/3284943

根据他的建议，我创建了这个：

在 JSF 文件中，我使用我的自定义转换器及其定义的属性，在运行时选择转换器和动态属性。这是来自动态 PrimeFaces 数据表的 sn-p：

<h:outputText rendered = "#{column.dateTime}" value="#{table[column.name]}">
    <f:converter converterId="runtimeConverterSelector" />
    <f:attribute name="converterId" value="#{column.converterName}" />
    <f:attribute name="pattern" value="#{column.converterPattern}" />
</h:outputText>

自定义转换器：

@FacesConverter ("runtimeConverterSelector")
public class RuntimeConverterSelector implements Converter {
    Converter delegateConverter;
    @Override
    public Object getAsObject(FacesContext context, UIComponent component, String value) {
        retrieveAttributes(component);
        return delegateConverter.getAsObject(context, component, value);
    }
    @Override
    public String getAsString(FacesContext context, UIComponent component, Object value) {
        retrieveAttributes(component);
        return delegateConverter.getAsString(context, component, value);
    }
    private void retrieveAttributes(UIComponent component) {
        Object attribute;
        attribute = component.getAttributes().get("converterId");
        if (attribute != null) {
            String converterName = (String)attribute;
            switch (converterName) {
                case "javax.faces.BigDecimal":
                    delegateConverter = new BigDecimalConverter();
                    break;
                case "javax.faces.BigInteger":
                    delegateConverter = new BigIntegerConverter();
                    break;
                case "javax.faces.Boolean":
                    delegateConverter = new BooleanConverter();
                    break;
                case "javax.faces.Byte":
                    delegateConverter = new ByteConverter();
                    break;
                case "javax.faces.Character":
                    delegateConverter = new CharacterConverter();
                    break;
                case "javax.faces.DateTimeConverter":
                    delegateConverter = new DateTimeConverter();
                    attribute = component.getAttributes().get("pattern");
                    if (attribute != null) ((DateTimeConverter)delegateConverter).setPattern((String)attribute);
                    attribute = component.getAttributes().get("timeZone");
                    if (attribute != null) ((DateTimeConverter)delegateConverter).setTimeZone(TimeZone.getTimeZone((String)attribute));
                    attribute = component.getAttributes().get("dateStyle");
                    if (attribute != null) ((DateTimeConverter)delegateConverter).setDateStyle((String)attribute);
                    attribute = component.getAttributes().get("timeStyle");
                    if (attribute != null) ((DateTimeConverter)delegateConverter).setDateStyle((String)attribute);
                    attribute = component.getAttributes().get("type");
                    if (attribute != null) ((DateTimeConverter)delegateConverter).setDateStyle((String)attribute);
                    break;
                case "javax.faces.Double":
                    delegateConverter = new DoubleConverter();
                    break;
                case "javax.faces.Enum":
                    delegateConverter = new EnumConverter();
                    break;
                case "javax.faces.Float":
                    delegateConverter = new FloatConverter();
                    break;
                case "javax.faces.Integer":
                    delegateConverter = new IntegerConverter();
                    break;
                case "javax.faces.Long":
                    delegateConverter = new LongConverter();
                    break;
                case "javax.faces.Number":
                    delegateConverter = new NumberConverter();
                    attribute = component.getAttributes().get("currencyCode");
                    if (attribute != null) ((NumberConverter)delegateConverter).setCurrencyCode((String)attribute);
                    attribute = component.getAttributes().get("currencySymbol");
                    if (attribute != null) ((NumberConverter)delegateConverter).setCurrencySymbol((String)attribute);
                    attribute = component.getAttributes().get("groupingUsed");
                    if (attribute != null) ((NumberConverter)delegateConverter).setGroupingUsed(Boolean.parseBoolean((String)attribute));
                    attribute = component.getAttributes().get("integerOnly");
                    if (attribute != null) ((NumberConverter)delegateConverter).setIntegerOnly(Boolean.parseBoolean((String)attribute));
                    attribute = component.getAttributes().get("locale");
                    if (attribute != null) ((NumberConverter)delegateConverter).setLocale(new Locale((String)attribute));
                    attribute = component.getAttributes().get("maxFractionDigits");
                    if (attribute != null) ((NumberConverter)delegateConverter).setMaxFractionDigits(Integer.parseInt((String)attribute));
                    attribute = component.getAttributes().get("maxIntegerDigits");
                    if (attribute != null) ((NumberConverter)delegateConverter).setMaxIntegerDigits(Integer.parseInt((String)attribute));
                    attribute = component.getAttributes().get("minFractionDigits");
                    if (attribute != null) ((NumberConverter)delegateConverter).setMinFractionDigits(Integer.parseInt((String)attribute));
                    attribute = component.getAttributes().get("minIntegerDigits");
                    if (attribute != null) ((NumberConverter)delegateConverter).setMinIntegerDigits(Integer.parseInt((String)attribute));
                    attribute = component.getAttributes().get("pattern");
                    if (attribute != null) ((NumberConverter)delegateConverter).setPattern((String)attribute);
                    attribute = component.getAttributes().get("type");
                    if (attribute != null) ((NumberConverter)delegateConverter).setType((String)attribute);
                    break;
                case "javax.faces.Short":
                    delegateConverter = new ShortConverter();
                    break;
                default:
                    System.err.println("ConverterId provided to runtimeConverterSelector, '" + converterName + "' is invalid. The default converter will be used");
                    break;
            }
        } else {
            System.err.println("No converterId was provided to runtimeConverterSelector.  The default converter will be used.");
        }
    }
}

Answer 2

AFAIK 这是不可能的。但是您可以在一个转换器中检查这两种格式。当然，转换为字符串将基于一种格式完成。或者，您可以根据当前的Locale 格式化日期。基本示例：

@FacesConverter("doubleDateConverter")
public class DateConverter implements Converter {

    public Object getAsObject(FacesContext context, UIComponent component, String value) {
        if(value == null || value.equals("")) {
            return null;
        }
        SimpleDateFormat format1 = new SimpleDateFormat("ddMMyyyy");
        SimpleDateFormat format2 = new SimpleDateFormat("yyyyMMdd");
        Date date = null;
        boolean valid = true;
        try {
            date = format1.parse(value);
        } catch (ParseException e) {
            valid = false;
        }
        if(!valid) {
            try {
                date = format2.parse(value);
            } catch (ParseException e) {
                valid = false;
            }
        }
        if((!valid) || (date == null)) {
            throw new ConverterException(new FacesMessage("Date is in wrong format: " + value));
        }
        return date;
    }

    public String getAsString(FacesContext context, UIComponent component, Object value) {
        if (!(value instanceof Date) || (value == null)) {
            return null;
        }
        SimpleDateFormat format = new SimpleDateFormat("ddMMyyyy");
        return format.format((Date)value);
    }

}