jsf - 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决定动态使用哪个？就像“如果单击此命令按钮，请使用此转换器，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 数据表的片段：

<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. 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);
    }

}