B.4. Coding a BeanDefinitionParser

A BeanDefinitionParser will be used if the NamespaceHandler encounters an XML element of the type that has been mapped to the specific bean definition parser (which is 'dateformat' in this case). In other words, the BeanDefinitionParser is responsible for parsing one distinct top-level XML element defined in the schema. In the parser, we'll have access to the XML element (and thus it's subelements too) so that we can parse our custom XML content, as can be seen in the following example:

package org.springframework.samples.xml;

import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.xml.AbstractSingleBeanDefinitionParser;
import org.springframework.util.StringUtils;
import org.w3c.dom.Element;

import java.text.SimpleDateFormat;

public class SimpleDateFormatBeanDefinitionParser extends AbstractSingleBeanDefinitionParser { 

   protected Class getBeanClass(Element element) {
      return SimpleDateFormat.class; 
   }

   protected void doParse(Element element, BeanDefinitionBuilder bean) {
      // this will never be null since the schema explicitly requires that a value be supplied
      String pattern = element.getAttribute("pattern");
      bean.addConstructorArg(pattern);

      // this however is an optional property
      String lenient = element.getAttribute("lenient");
      if (StringUtils.hasText(lenient)) {
         bean.addPropertyValue("lenient", Boolean.valueOf(lenient));
      }
   }
}

	We use the Spring-provided AbstractSingleBeanDefinitionParser to handle a lot of the basic grunt work of creating a single BeanDefinition.
	We supply the AbstractSingleBeanDefinitionParser superclass with the type that our single BeanDefinition will represent.

In this simple case, this is all that we need to do. The creation of our single BeanDefinition is handled by the AbstractSingleBeanDefinitionParser superclass, as is the extraction and setting of the bean definition's unique identifier.