java f:convertDateTime 是否支持 Java8 LocalDate / LocalDateTime？
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f:convertDateTime support for Java8 LocalDate / LocalDateTime?
提问by alfonx
The JSF Core Tag f:convertDateTimecan format java.util.Dateobjects. The Date class has many deprecated methods and with Java 8 come new classes to present local dates and times: LocalDateTimeand LocalDate.
JSF 核心标签f:convertDateTime可以格式化java.util.Date对象。Date 类有许多不推荐使用的方法，Java 8 提供了新的类来显示本地日期和时间：LocalDateTime和LocalDate。
f:convertDateTimecan not format LocalDateTimenor LocalDate.
f:convertDateTime不能格式化LocalDateTime或LocalDate。
Does anybody know, if there is an equivalent to the JSF core tag convertDateTime that can deal with LocalDateTime objects? Is support planned for a future release, or are alternative tags available?
有人知道，是否有等效于 JSF 核心标记 convertDateTime 可以处理 LocalDateTime 对象？是否计划为未来版本提供支持，或者是否有替代标签可用？
回答by hinneLinks
Just write your own Converter and extend the javax.faces.convert.DateTimeConverter- that way you can Reuse all the attributes that <f:convertDateTime>supports. Also it will take care of Localization too. Unfortunately it's a bit more complicated to write a Converter with Attributes.
只需编写您自己的转换器并扩展javax.faces.convert.DateTimeConverter- 这样您就可以重用所有<f:convertDateTime>支持的属性。它也将负责本地化。不幸的是，编写带有属性的转换器有点复杂。
Create component
First write your own Converter that extends javax.faces.convert.DateTimeConverter- just let the super-calls do all the work (including locale-stuff) and convert the result from/to LocalDate.
创建组件
首先编写您自己的扩展转换器javax.faces.convert.DateTimeConverter- 只需让超级调用完成所有工作（包括语言环境）并将结果从/到 LocalDate 转换。
@FacesConverter(value = LocalDateConverter.ID)
public class LocalDateConverter extends DateTimeConverter {
public static final String ID = "com.example.LocalDateConverter";
@Override
public Object getAsObject(FacesContext facesContext, UIComponent uiComponent, String value) {
Object o = super.getAsObject(facesContext, uiComponent, value);
if (o == null) {
return null;
}
if (o instanceof Date) {
Instant instant = Instant.ofEpochMilli(((Date) o).getTime());
return LocalDateTime.ofInstant(instant, ZoneId.systemDefault()).toLocalDate();
} else {
throw new IllegalArgumentException(String.format("value=%s could not be converted to a LocalDate, result super.getAsObject=%s", value, o));
}
}
@Override
public String getAsString(FacesContext facesContext, UIComponent uiComponent, Object value) {
if (value == null) {
return super.getAsString(facesContext, uiComponent,value);
}
if (value instanceof LocalDate) {
LocalDate lDate = (LocalDate) value;
Instant instant = lDate.atStartOfDay().atZone(ZoneId.systemDefault()).toInstant();
Date date = Date.from(instant);
return super.getAsString(facesContext, uiComponent, date);
} else {
throw new IllegalArgumentException(String.format("value=%s is not a instanceof LocalDate", value));
}
}
}
Then create a file LocalDateConverter-taglib.xmlin META-INF:
然后LocalDateConverter-taglib.xml在META-INF以下位置创建一个文件：
<facelet-taglib version="2.2"
xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-facelettaglibrary_2_2.xsd">
<namespace>http://example.com/LocalDateConverter</namespace>
<tag>
<tag-name>convertLocalDate</tag-name>
<converter>
<converter-id>com.example.LocalDateConverter</converter-id>
</converter>
</tag>
</facelet-taglib>
And lastly, register the taglib in web.xml:
最后，在web.xml以下位置注册 taglib ：
<context-param>
<param-name>javax.faces.FACELETS_LIBRARIES</param-name>
<param-value>/META-INF/LocalDateConverter-taglib.xml</param-value>
</context-param>
Usage
To use the new Tag in your JSF-Page add the new Taglib xmlns:ldc="http://example.com/LocalDateConverter"and use the tag:
用法
要在您的 JSF-Page 中使用新标签，请添加新的 Taglibxmlns:ldc="http://example.com/LocalDateConverter"并使用该标签：
<ldc:convertLocalDate type="both" dateStyle="full"/>
