如何为 h:dataTable/ui:repeat 的每一行/项目设置转换器属性? [英] How to set converter properties for each row/item of h:dataTable/ui:repeat?

问题描述

我创建了一个自定义的 ISO 日期时间 Converter:

public class IsoDateTimeConverter 实现了 Converter，StateHolder {私有类类型；私有字符串模式；私有布尔瞬态值 = 假；公共无效集类型(类类型){this.type = 类型；}公共无效setPattern(字符串模式){this.pattern = 模式；}@覆盖public Object getAsObject(FacesContext context, UIComponent component, String value) 抛出 ConverterException {如果(StringCheck.isNullOrEmpty(值)){throw new ConverterException("未指定值");}尝试 {如果(IsoDate.class.equals(类型)){如果(WebConst.ISO_DATE_NONE.equals(值)){返回 IsoDate.DUMMY;} 别的 {//TODO User spezifische TimeZone auslesen返回新的 IsoDate(value, TimeZone.getDefault().getID());}} else if (IsoTime.class.equals(type)) {如果(WebConst.ISO_TIME_NONE.equals(值)){返回 IsoTime.DUMMY;} 别的 {//TODO User spezifische TimeZone auslesen返回新的 IsoTime(value, TimeZone.getDefault().getID());}} else if (IsoTimestamp.class.equals(type)) {如果(WebConst.ISO_TIMESTAMP_NONE.equals(值)){返回 IsoTimestamp.DUMMY;} 别的 {//TODO User spezifische TimeZone auslesen返回新的 IsoTimestamp(value, TimeZone.getDefault().getID());}} 别的 {throw new ConverterException("值不可转换");}} 捕获(异常 e){throw new ConverterException(e.getMessage());}}@覆盖public String getAsString(FacesContext context, UIComponent component, Object value) 抛出 ConverterException {如果(值 == 空){throw new ConverterException("未指定值");}如果 (IsoDate.class.equals(value)) {IsoDate isoDate = (IsoDate) 值；如果(isoDate.isDummy()){返回 WebConst.ISO_DATE_NONE;} 别的 {//TODO User spezifische TimeZone auslesen返回 isoDate.toString(pattern, TimeZone.getDefault().getID(), false);}} else if (IsoTime.class.equals(value)) {IsoTime isoTime = (IsoTime) 值；如果(isoTime.isDummy()){返回 WebConst.ISO_TIME_NONE;} 别的 {//TODO User spezifische TimeZone auslesen返回 isoTime.toString(pattern, TimeZone.getDefault().getID(), false);}} else if (IsoTimestamp.class.equals(value)) {IsoTimestamp isoTimestamp = (IsoTimestamp) 值；如果(isoTimestamp.isDummy()){返回 WebConst.ISO_TIMESTAMP_NONE;} 别的 {//TODO User spezifische TimeZone auslesenreturn isoTimestamp.toString(pattern, TimeZone.getDefault().getID(), false);}} 别的 {throw new ConverterException("值不可转换");}}@覆盖公共对象 saveState(FacesContext 上下文){返回新对象[]{类型，模式}；}@覆盖public void restoreState(FacesContext上下文，对象状态){type = (Class) ((Object[]) state)[0];模式=(字符串)((对象[])状态)[1]；}@覆盖公共布尔 isTransient() {返回瞬态值；}@覆盖公共无效setTransient(布尔瞬态值){this.transientValue = 瞬态值；}}

我在以下视图中使用 Converter 作为 :

<p:列><h:outputText value="#{item.balanceDate}"immediate="true"><mh:IsoDateTimeConverter type="#{webConst.ISO_DATE_CLASS}" pattern="#{webConst.ISO_DATE_FORMAT}"/></h:outputText></p:列></p:dataTable>

问题是，当我第一次打开这个视图时，所有属性只在我的 Converter 类中设置一次，然后数据表根据初始属性呈现和转换值.

我希望属性是按行设置的.我怎样才能做到这一点?

解决方案

到目前为止，您希望每次呈现数据表行时都会设置转换器的属性.这确实不是真的.在构建视图时，JSF 将只为每个组件创建一个转换器实例，它不会在每次呈现行时创建/重置转换器.

有几种方法可以让它工作.

• 将动态属性作为组件的 传递，并让 Converter 拦截它.你可以在这里找到一个例子:JSF convertDateTime with timezone in datatable.这可以用作

  <f:converter converterId="isoDateTimeConverter"/><f:attribute name="pattern" value="#{item.pattern}"/></h:outputText>

  ---

• 使用 EL 函数代替 Converter.你可以在这里找到一个例子:Facelets 和 JSTL(将日期转换为用于字段的字符串).这可以用作

  <h:outputText value="#{mh:convertIsoDate(item.balanceDate, item.pattern)}"/>

  ---

• 将转换器和数据表的 DataModel 绑定为同一托管 bean 的属性.通过这种方式，您将能够在返回之前根据行数据设置转换器的属性.这是一个基于标准 JSF 组件和标准 DateTimeConverter 的基本启动示例(它应该在 PrimeFaces 组件和您的自定义转换器上同样有​​效):

  <h:列><h:outputText value="#{item.date}" converter="#{bean.converter}"/></h:列></h:dataTable>

  与

  @ManagedBean@ViewScoped公共类 Bean 实现了 Serializable {私人列表<项目>项目;私有数据模型模型;私有 DateTimeConverter 转换器；@PostConstruct公共无效初始化(){项目 = Arrays.asList(新项目(新日期()，dd-MM-yyyy")，新项目(新日期()，yyyy-MM-dd")，新项目(新日期()，MM/dd/yyyy"))；模型 = 新的 ListDataModel(items);转换器 = 新的 DateTimeConverter();}公共数据模型获取模型(){退货模式；}公共转换器 getConverter() {转换器.setPattern(model.getRowData().getPattern());返回转换器；}}

  (Item 类只是一个 bean，具有两个属性 Date date 和 String pattern)

  结果是

  <块引用>

  23-09-2011
  2011-09-23
  09/23/2011

  ---

• 改用 OmniFaces .它支持属性中 EL 的渲染时间评估.另请参阅 展示示例.

  <o:converter converterId="isoDateTimeConverter" pattern="#{item.pattern}"/></h:outputText>

I have created a custom ISO date time Converter:

public class IsoDateTimeConverter implements Converter, StateHolder {

    private Class type;
    private String pattern;

    private boolean transientValue = false;

    public void setType(Class type) {
        this.type = type;
    }

    public void setPattern(String pattern) {
        this.pattern = pattern;
    }

    @Override
    public Object getAsObject(FacesContext context, UIComponent component, String value) throws ConverterException {
        if (StringCheck.isNullOrEmpty(value)) {
            throw new ConverterException("value not specified");
        }

        try {
            if (IsoDate.class.equals(type)) {

                if (WebConst.ISO_DATE_NONE.equals(value)) {
                    return IsoDate.DUMMY;
                } else {
                    //TODO User spezifische TimeZone auslesen
                    return new IsoDate(value, TimeZone.getDefault().getID());
                }

            } else if (IsoTime.class.equals(type)) {

                if (WebConst.ISO_TIME_NONE.equals(value)) {
                    return IsoTime.DUMMY;
                } else {
                    //TODO User spezifische TimeZone auslesen
                    return new IsoTime(value, TimeZone.getDefault().getID());
                }

            } else if (IsoTimestamp.class.equals(type)) {

                if (WebConst.ISO_TIMESTAMP_NONE.equals(value)) {
                    return IsoTimestamp.DUMMY;
                } else {
                    //TODO User spezifische TimeZone auslesen
                    return new IsoTimestamp(value, TimeZone.getDefault().getID());
                }

            } else {
                throw new ConverterException("value not convertible");
            }
        } catch (Exception e) {
            throw new ConverterException(e.getMessage());
        }
    }

    @Override
    public String getAsString(FacesContext context, UIComponent component, Object value) throws ConverterException {
        if (value == null) {
            throw new ConverterException("value not specified");
        }

        if (IsoDate.class.equals(value)) {
            IsoDate isoDate = (IsoDate) value;

            if (isoDate.isDummy()) {
                return WebConst.ISO_DATE_NONE;
            } else {
                //TODO User spezifische TimeZone auslesen
                return isoDate.toString(pattern, TimeZone.getDefault().getID(), false);
            }

        } else if (IsoTime.class.equals(value)) {
            IsoTime isoTime = (IsoTime) value;

            if (isoTime.isDummy()) {
                return WebConst.ISO_TIME_NONE;
            } else {
                //TODO User spezifische TimeZone auslesen
                return isoTime.toString(pattern, TimeZone.getDefault().getID(), false);
            }

        } else if (IsoTimestamp.class.equals(value)) {
            IsoTimestamp isoTimestamp = (IsoTimestamp) value;

            if (isoTimestamp.isDummy()) {
                return WebConst.ISO_TIMESTAMP_NONE;
            } else {
                //TODO User spezifische TimeZone auslesen
                return isoTimestamp.toString(pattern, TimeZone.getDefault().getID(), false);
            }

        } else {
            throw new ConverterException("value not convertible");
        }
    }

    @Override
    public Object saveState(FacesContext context) {
        return new Object[]{type, pattern};
    }

    @Override
    public void restoreState(FacesContext context, Object state) {
        type = (Class) ((Object[]) state)[0];
        pattern = (String) ((Object[]) state)[1];
    }

    @Override
    public boolean isTransient() {
        return transientValue;
    }

    @Override
    public void setTransient(boolean transientValue) {
        this.transientValue = transientValue;
    }
}

And I use the Converter as <mh:IsoDateTimeConverter> in the following view:

<p:dataTable value="#{imports.list}" var="item">
    <p:column>
        <h:outputText value="#{item.balanceDate}" immediate="true">
            <mh:IsoDateTimeConverter type="#{webConst.ISO_DATE_CLASS}" pattern="#{webConst.ISO_DATE_FORMAT}"/>
        </h:outputText>
    </p:column>
</p:dataTable>

The problem is, when I first open this view, all properties are set in my Converter class only once and then the datatable renders and converts the values based on initial properties.

I expected that the properties are set on a per-row basis. How can I achieve this?

解决方案

To the point, you expected that the converter's properties are set every time a datatable row is rendered. This is indeed not true. JSF will create only one converter instance per component when the view is to be built, it will not create/reset the converter each time the row is rendered.

There are several ways to get it to work.

• Pass the dynamic attributes as <f:attribute> of the component and let the Converter intercept on that. You can find an example here: JSF convertDateTime with timezone in datatable. This can then be used as

  <h:outputText value="#{item.balanceDate}">
      <f:converter converterId="isoDateTimeConverter" />
      <f:attribute name="pattern" value="#{item.pattern}" />
  </h:outputText>
  

  ---

• Use an EL function instead of a Converter. You can find an example here: Facelets and JSTL (Converting a Date to a String for use in a field). This can then be used as

  <h:outputText value="#{mh:convertIsoDate(item.balanceDate, item.pattern)}" />
  

  ---

• Bind the converter and datatable's DataModel as a property of the same managed bean. This way you will be able to set the converter's properties based on the row data before returning it. Here's a basic kickoff example based on standard JSF components and standard DateTimeConverter (it should work equally good on PrimeFaces components and with your custom converter):

  <h:dataTable value="#{bean.model}" var="item">
      <h:column>
          <h:outputText value="#{item.date}" converter="#{bean.converter}" />
      </h:column>
  </h:dataTable>
  

  with

  @ManagedBean
  @ViewScoped
  public class Bean implements Serializable {
  
      private List<Item> items;
      private DataModel<Item> model;
      private DateTimeConverter converter;
  
      @PostConstruct
      public void init() {
          items = Arrays.asList(
              new Item(new Date(), "dd-MM-yyyy"), 
              new Item(new Date(), "yyyy-MM-dd"), 
              new Item(new Date(), "MM/dd/yyyy"));
          model = new ListDataModel<Item>(items);
          converter = new DateTimeConverter();
      }
  
      public DataModel<Item> getModel() {
          return model;
      }
  
      public Converter getConverter() {
          converter.setPattern(model.getRowData().getPattern());
          return converter;
      }
  
  }
  

  (the Item class is just a bean with two properties Date date and String pattern)

  this results in

  23-09-2011
  2011-09-23
  09/23/2011

  ---

• Use OmniFaces <o:converter> instead. It supports render time evaluation of EL in the attributes. See also the <o:converter> showcase example.

  <h:outputText value="#{item.balanceDate}">
      <o:converter converterId="isoDateTimeConverter" pattern="#{item.pattern}" />
  </h:outputText>
  

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