/*
 * Copyright 2005-2014 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.xml.xpath;

import java.util.Map;

import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;

/**
 * Spring {@link FactoryBean} for {@link XPathExpression} object. Facilitates injection of XPath expressions into
 * endpoint beans.
 *
 * <p>Uses {@link XPathExpressionFactory} underneath, so support is provided for JAXP 1.3, and Jaxen XPaths.
 *
 * @author Arjen Poutsma
 * @see #setExpression(String)
 * @since 1.0.0
 */
public class XPathExpressionFactoryBean implements FactoryBean<XPathExpression>, InitializingBean {

	private Map<String, String> namespaces;

	private String expressionString;

	private XPathExpression expression;

	/** Sets the XPath expression. Setting this property is required. */
	public void setExpression(String expression) {
		expressionString = expression;
	}

	/** Sets the namespaces for the expressions. The given properties binds string prefixes to string namespaces. */
	public void setNamespaces(Map<String, String> namespaces) {
		this.namespaces = namespaces;
	}

	@Override
	public void afterPropertiesSet() throws IllegalStateException, XPathParseException {
		Assert.notNull(expressionString, "expression is required");
		if (CollectionUtils.isEmpty(namespaces)) {
			expression = XPathExpressionFactory.createXPathExpression(expressionString);
		}
		else {
			expression = XPathExpressionFactory.createXPathExpression(expressionString, namespaces);
		}
	}

	@Override
	public XPathExpression getObject() throws Exception {
		return expression;
	}

	@Override
	public Class<? extends XPathExpression> getObjectType() {
		return XPathExpression.class;
	}

	@Override
	public boolean isSingleton() {
		return true;
	}
}