XpathReturnType.java

/*
 * Copyright 2011 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.xmlmatchers.xpath;

import javax.xml.namespace.QName;
import javax.xml.xpath.XPathConstants;

/**
 * The type of value returned from an XPath expression. This value can be fed to
 * additional matchers after being extracted from an XML document via an XPath
 * query. For example:
 * 
 * {@code
 * 		assertThat(xml, hasXPath("count(/mountains/mountain)", equalTo("2")));
		assertThat(xml,//
				hasXPath("count(/mountains/mountain)", //
						returningANumber(), //
						greaterThanOrEqualTo(2d)));
 * }
 * 
 * @author David Ehringer
 */
public abstract class XpathReturnType<T> {

	protected abstract QName evaluationMode();

	public static XpathReturnType<Double> returningANumber() {
		return new XpathReturnType<Double>() {
			@Override
			protected QName evaluationMode() {
				return XPathConstants.NUMBER;
			}
		};
	}

	/**
	 * Warning: The return type passed to subsequent matchers will actually be a
	 * Source rather than a Node. Returning a Node is not particularly useful
	 * because it is nearly impossible to create any useful matchers for Node.
	 * This is a slight inconsistency in naming but makes the result much more
	 * usable.
	 * 
	 */
	public static XpathReturnType<String> returningAnXmlNode() {
		return new XpathReturnType<String>() {
			@Override
			protected QName evaluationMode() {
				return XPathConstants.NODE;
			}
		};
	}

	public static XpathReturnType<String> returningAString() {
		return new XpathReturnType<String>() {
			@Override
			protected QName evaluationMode() {
				return XPathConstants.STRING;
			}
		};
	}

	public static XpathReturnType<Boolean> returningABoolean() {
		return new XpathReturnType<Boolean>() {
			@Override
			protected QName evaluationMode() {
				return XPathConstants.BOOLEAN;
			}
		};
	}
}