/*
* $Id: ConverterELTag.java,v 1.9 2007/04/27 22:00:11 ofung Exp $
*/
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package javax.faces.webapp;
import javax.faces.component.UIComponent;
import javax.faces.component.ValueHolder;
import javax.faces.context.FacesContext;
import javax.faces.convert.Converter;
import javax.faces.convert.ConverterException;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
/**
* <p><strong>ConverterELTag</strong> is a base class for all JSP custom
* actions that create and register a <code>Converter</code> instance on
* the {@link ValueHolder} associated with our most immediate
* surrounding instance of a tag whose implementation class is a
* subclass of {@link UIComponentClassicTagBase}. To avoid creating duplicate
* instances when a page is redisplayed, creation and registration of a
* {@link Converter} occurs <strong>only</strong> if the corresponding
* {@link UIComponent} was created (by the owning {@link
* UIComponentTag}) during the execution of the current page.</p>
*
* <p>This class may be used as a base class for tag instances that
* support specific {@link Converter} subclasses.</p>
*
* <p>Subclasses of this class must implement the
* <code>createConverter()</code> method, which creates and returns a
* {@link Converter} instance. Any configuration properties that specify
* behavior of this {@link Converter} must have been set by the
* <code>createConverter()</code> method. Generally, this occurs
* by copying corresponding attribute values on the tag instance.</p>
*
* <p>This tag creates no output to the page currently being created. It
* is used solely for the side effect of {@link Converter} creation.</p>
*
*/
public abstract class ConverterELTag extends TagSupport {
// ---------------------------------------------------------- Public Methods
/**
* <p>Create a new instance of the specified {@link Converter}
* class, and register it with the {@link UIComponent} instance associated
* with our most immediately surrounding {@link UIComponentClassicTagBase} instance, if
* the {@link UIComponent} instance was created by this execution of the
* containing JSP page. If the localValue of the
* {@link UIComponent} is a String, attempt to convert it.</p></p>
*
* @throws JspException if a JSP error occurs
*/
public int doStartTag() throws JspException {
// Locate our parent UIComponentTag
UIComponentClassicTagBase tag =
UIComponentClassicTagBase.getParentUIComponentClassicTagBase(pageContext);
if (tag == null) { // PENDING - i18n
throw new JspException("Not nested in a UIComponentTag Error for tag with handler class:"+
this.getClass().getName());
}
// Nothing to do unless this tag created a component
if (!tag.getCreated()) {
return (SKIP_BODY);
}
UIComponent component = tag.getComponentInstance();
if (component == null) {
//PENDING i18n
throw new JspException("Can't create Component from tag.");
}
if (!(component instanceof ValueHolder)) {
//PENDING i18n
throw new JspException("Not nested in a tag of proper type. Error for tag with handler class:"+
this.getClass().getName());
}
Converter converter = createConverter();
if (converter == null) {
throw new JspException("Can't create class of type:"+
" javax.faces.convert.Converter, converter is null");
}
ValueHolder vh = (ValueHolder)component;
FacesContext context = FacesContext.getCurrentInstance();
// Register an instance with the appropriate component
vh.setConverter(converter);
// Once the converter has been set, attempt to convert the
// incoming "value"
Object localValue = vh.getLocalValue();
if (localValue instanceof String) {
try {
localValue = converter.getAsObject(context, (UIComponent)vh, (String) localValue);
vh.setValue(localValue);
}
catch (ConverterException ce) {
// PENDING - Ignore? Throw an exception? Set the local
// value back to "null" and log a warning?
}
}
return (SKIP_BODY);
}
// ------------------------------------------------------- Protected Methods
/**
* <p>Create and return a new {@link Converter} to be registered
* on our surrounding {@link UIComponent}.</p>
*
* @throws JspException if a new instance cannot be created
*/
protected abstract Converter createConverter()
throws JspException;
}