Creating custom tag for Converter with attributes

问题

I have found a Converter online and changed it to my needs as far as I could. The problem is though that I need to add a flag (i.e. a string) that must be checked and than the converter must apply a certain pattern to a string.

Custom Converter:

@FacesConverter("convtest.UrlConverter")
public class UrlConverter implements Converter {

   @Override
   public Object getAsObject(FacesContext facesContext, UIComponent component, String value) {

      StringBuilder url = new StringBuilder();

      if(value!=null){
          if(value.length()==13){
              String tempstring;
              tempstring=value.toString();
              String finalstring= tempstring.substring(0, 4) + "-" + tempstring.substring(4, 8) + "-" + tempstring.substring(8, 13);
              url.append(finalstring);

          }else{
              url.append(value);
          }
      }else
     url.append("");

      try {
         new URI(url.toString());           
      } catch (URISyntaxException e) {

        return null;
      }

      UrlData urlData = new UrlData(url.toString()); 
      return urlData;
   }

   @Override
   public String getAsString(FacesContext facesContext,
      UIComponent component, Object value) {
         try {
            return value.toString();
        } catch (Exception e) {
            return null;
        }
   }


}

XHTML:

 <h:inputText value="#{userData.data}">
    <f:converter converterId="convtest.UrlConverter" />
 </h:inputText>

Now the problem is that for example I have 2 conversion types:

hju
zurt

Let's say that hju have the output format XXXX-XXXX-XXXXX and zurt has the output format XX-XX-XX-XX-XX-XX-X.

Now I would like to call the converter like for example:

 <f:converter converterId="convtest.UrlConverter" type="hju" />

Or something like that and get it to use the correct pattern.

Any ideas on how to do this?

回答1:

You need to register the custom converter as a new tag in *.taglib.xml wherein you can specify as many attributes as you want which will then be mapped as bean properties of the converter instance.

So, given a new property type:

@FacesConverter("convtest.UrlConverter")
public class UrlConverter implements Converter {

    private String type; // +getter+setter

}

And this /WEB-INF/my.taglib.xml (assuming JSF 2.x on Facelets):

<?xml version="1.0" encoding="UTF-8"?>
<facelet-taglib
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-facelettaglibrary_2_0.xsd"
    version="2.0"
>
    <namespace>http://example.com/ui</namespace>

    <tag>
        <tag-name>urlConverter</tag-name>
        <converter>
            <converter-id>convtest.UrlConverter</converter-id>
        </converter>
        <attribute>
            <name>type</name>
            <type>java.lang.String</type>
        </attribute>
    </tag>
</facelet-taglib>

Which is registered as below in /WEB-INF/web.xml:

<context-param>
    <param-name>javax.faces.FACELETS_LIBRARIES</param-name>
    <param-value>/WEB-INF/my.taglib.xml</param-value>
</context-param>

Then this usage should do:

<html ... xmlns:my="http://example.com/ui">
...
<h:inputText ...>
    <my:urlConverter type="hju" />
</h:inputText>

<html ... xmlns:my="http://example.com/ui">
...
<h:inputText ...>
    <my:urlConverter type="zurt" />
</h:inputText>

Alternatively, if you happen to use JSF utility library OmniFaces, then you can also save the above XML boilerplate by using <o:converter> as below:

<html ... xmlns:o="http://omnifaces.org/ui">
...
<h:inputText ...>
    <o:converter converterId="convtest.UrlConverter" type="hju" />
</h:inputText>

<html ... xmlns:o="http://omnifaces.org/ui">
...
<h:inputText ...>
    <o:converter converterId="convtest.UrlConverter" type="zurt" />
</h:inputText>

It will transparently set those attributes as converter properties.

回答2:

You should use <f:attribute/>

<h:outputText value="#{userData.data}" >
  <f:converter converterId="convtest.UrlConverter" />
  <f:attribute name="myCoolFlag" value="hju"/>
</h:outputText>

In the converter you can call component.getAttributes().get("myCoolFlag");

来源：https://stackoverflow.com/questions/31406474/creating-custom-tag-for-converter-with-attributes

标签

jsf

attributes

converter