D-Net

package eu.dnetlib.springutils.condbean;

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

import org.springframework.beans.factory.config.BeanDefinition;

import org.springframework.beans.factory.config.BeanDefinitionHolder;

import org.springframework.beans.factory.support.BeanDefinitionReaderUtils;

import org.springframework.beans.factory.xml.BeanDefinitionParser;

import org.springframework.beans.factory.xml.BeanDefinitionParserDelegate;

import org.springframework.beans.factory.xml.ParserContext;

import org.springframework.core.io.ResourceLoader;

import org.springframework.core.io.support.ResourcePatternResolver;

import org.springframework.core.io.support.ResourcePatternUtils;

import org.springframework.util.xml.DomUtils;

import org.w3c.dom.Element;

import com.google.common.collect.Lists;

import eu.dnetlib.springutils.condbean.parser.CondBeanParser;

import eu.dnetlib.springutils.condbean.parser.RunccExpressionParser;

/**

 * Taken from http://robertmaldon.blogspot.com/2007/04/conditionally-defining-spring-beans.html .

 * 

 * modified to fix a problem caused by http://jira.springframework.org/browse/SPR-2955 improved expression parsing

 * 

 * @author marko

 * 

 */

public class ConditionalBeanDefinitionParser implements BeanDefinitionParser {

	/**

	 * logger.

	 */

	@SuppressWarnings("unused")

	// NOPMD by marko on 11/24/08 5:02 PM

	private static final Log log = LogFactory.getLog(ConditionalBeanDefinitionParser.class);

	/**

	 * expression parser.

	 */

	private transient RunccExpressionParser expressionParser = null;

	public void init(ResourceLoader resourceLoader) {

		if(expressionParser != null)

			return;

		final ResourcePatternResolver resolver = ResourcePatternUtils.getResourcePatternResolver(resourceLoader);

		ChainPropertyFinder chain = new ChainPropertyFinder();

		ResourcePropertyFinder res1 = new ResourcePropertyFinder();

		res1.setResource(resolver.getResource("classpath:/eu/dnetlib/cnr-default.properties"));

		ResourcePropertyFinder res2 = new ResourcePropertyFinder();

		res2.setResource(resolver.getResource("classpath:/eu/dnetlib/cnr-site.properties"));

		ResourcePropertyFinder res3 = new ResourcePropertyFinder();

		res3.setResource(resolver.getResource("classpath:/cnr-override.properties"));

		chain.setFinders(Lists.newArrayList(new SystemPropertiesFinder(), res3, res2, res1));

		CondBeanParser condBeanParser = new CondBeanParser();

		condBeanParser.setPropertyFinder(chain);

		expressionParser = new RunccExpressionParser();

		expressionParser.setCondBeanParser(condBeanParser);

	}

	/**

	 * Parse the "cond" element and check the mandatory "test" attribute. If the system property named by test is null

	 * or empty (i.e. not defined) then return null, which is the same as not defining the bean.

	 * 

	 * @param element

	 *            element to parse

	 * @param parserContext

	 *            spring parser context

	 * @return registered bean or null.

	 */

	@Override

	public BeanDefinition parse(final Element element, final ParserContext parserContext) {

		init(parserContext.getReaderContext().getResourceLoader());

		if (DomUtils.nodeNameEquals(element, "cond")) {

			final String test = element.getAttribute("test");

			if (expressionParser.expressionValue(test)) {

				final Element beanElement = DomUtils.getChildElementByTagName(element, "bean");

				return parseAndRegisterBean(beanElement, parserContext);

			}

		}

		return null;

	}

	/**

	 * the real job of registering the child element of this conditional bean is performed here.

	 * 

	 * @param element

	 *            element

	 * @param parserContext

	 *            spring parser context

	 * @return registered bean.

	 */

	private BeanDefinition parseAndRegisterBean(final Element element, final ParserContext parserContext) {

		if (element == null)

			throw new IllegalStateException("trying to register a null bean");

		final BeanDefinitionParserDelegate delegate = parserContext.getDelegate();

		BeanDefinitionHolder holder = delegate.parseBeanDefinitionElement(element);

		BeanDefinitionReaderUtils.registerBeanDefinition(holder, parserContext.getRegistry());

		// necessary because of http://jira.springframework.org/browse/SPR-2955

		holder = delegate.decorateBeanDefinitionIfRequired(element, holder);

		return holder.getBeanDefinition();

	}

}