Dom4J example of creating an XML document from xpath and value information. Dependencies: Dom4J, Jaxen, Apache Commons, Log4J

1-generated.xml

<?xml version="1.0" encoding="ISO-8859-1"?>

<root>
  <data>
    <discharge_status>ACTIVE</discharge_status>
    <suspension_rec>
      <start>0815</start>
      <end>0115</end>
    </suspension_rec>
    <suspension_rec>
      <start>0915</start>
    </suspension_rec>
    <suspension_rec>
      <start>0115</start>
    </suspension_rec>
  </data>
</root>

DriverAppXMLService.java

/**
 * 
 */
package com.bmchild.service.driverapp.xml;


/**
 * @author bchild
 *
 */
public interface DriverAppXMLService {

  void buildXml();
}

DriverAppXmlServiceImpl.java

/**
 * 
 */
package com.bmchild.service.driverapp.xml;

import java.io.IOException;
import java.io.StringWriter;
import java.util.List;

import org.apache.log4j.Logger;
import org.dom4j.Document;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;
import org.dom4j.Node;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.XMLWriter;
import org.springframework.stereotype.Service;

/**
 * @author bchild
 *
 */
@Service
public class DriverAppXmlServiceImpl implements DriverAppXMLService {
  
	private static final Logger LOGGER = Logger.getLogger(DriverAppXmlServiceImpl.class.getName());
	
	private static final String ROOT = "root";
	private static final String BASE_XPATH = "/" + ROOT + "/data";

	/* (non-Javadoc)
	 * @see com.bmchild.service.driverapp.xml.DriverAppXMLService#buildXml()
	 */
	@Override
	public void buildXml() {
		Document document = DocumentHelper.createDocument(DocumentHelper.createElement(ROOT));

		addElementToParent(document, prependBase("/discharge_status"), "ACTIVE");
		addElementToParent(document, prependBase("/suspension_rec[2]/start"), "0915");
		addElementToParent(document, prependBase("/suspension_rec[1]/start"), "0815");
		addElementToParent(document, prependBase("/suspension_rec[3]/start"), "0115");
		addElementToParent(document, prependBase("/suspension_rec[1]/end"), "0115");
		
		printDoc(document);
		
	}
	
	/**
	 * @param string
	 * @return
	 */
	private String prependBase(String string) {
		return BASE_XPATH + string;
	}

	private void printDoc(Document document) {
		OutputFormat format = OutputFormat.createPrettyPrint();
		format.setEncoding("ISO-8859-1");
		StringWriter writer = new StringWriter();
		XMLWriter xmlwriter = new XMLWriter(writer, format);
		try {
			xmlwriter.write( document );
			LOGGER.debug(writer.getBuffer().toString());
		} catch (IOException e) {
			LOGGER.error(e.getMessage(), e);
		}
	}
	
	/**
	 * Recursive method to create an element and, if necessary, its parents and siblings
	 * @param document
	 * @param xpath to single element
	 * @param value if null an empty element will be created
	 * @return the created Node
	 */
	private Node addElementToParent(Document document, String xpath, String value) {
		if(LOGGER.isDebugEnabled()) {
			LOGGER.debug("adding Element: " + xpath + " -> " + value);
		}
		
		String elementName = XPathUtils.getChildElementName(xpath);
		String parentXPath = XPathUtils.getParentXPath(xpath);
		Node parentNode = document.selectSingleNode(parentXPath);
		if(parentNode == null) {
			parentNode = addElementToParent(document, parentXPath, null);
		}
		
		// create younger siblings if needed
		Integer childIndex = XPathUtils.getChildElementIndex(xpath);
		if(childIndex > 1) {
			List<?> nodelist = document.selectNodes(XPathUtils.createPositionXpath(xpath, childIndex));
			// how many to create = (index wanted - existing - 1 to account for the new element we will create)
			int nodesToCreate = childIndex - nodelist.size() - 1;
			for(int i = 0; i < nodesToCreate; i++) {
				((Element)parentNode).addElement(elementName);
			}
		}
		
		// create requested element
		Element created = ((Element)parentNode).addElement(elementName);
		if(null != value) {
			created.addText(value);
		}
		return created;
	}

}

DriverAppXmlServiceImplTest.java

/**
 * 
 */
package com.bmchild.service.driverapp.xml;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.InjectMocks;
import org.mockito.runners.MockitoJUnitRunner;

/**
 * @author bchild
 *
 */
@RunWith(MockitoJUnitRunner.class)
public class DriverAppXmlServiceImplTest {
  
	@InjectMocks
	private DriverAppXMLService driverAppXMLService = new DriverAppXmlServiceImpl();

	@Test
	public void testBuildXml() throws Exception {
		driverAppXMLService.buildXml();
	}

}

XPathUtils.java

/**
 * 
 */
package com.bmchild.service.driverapp.xml;

import org.apache.commons.lang3.StringUtils;

/**
 * @author bchild
 *
 */
public class XPathUtils {

  private static final String SLASH = "/";
	private static final String R_BRACKET = "]";
	private static final String L_BRACKET = "[";
	
	/**
	 * Looks for the last '/' and returns the name of the last element
	 * @param xpath
	 * @return the child element name or null
	 */
	public static final String getChildElementName(String xpath) {
		if(StringUtils.isEmpty(xpath)) {
			return null;
		}
		String childName = xpath.substring(xpath.lastIndexOf(SLASH) + 1);
		return stripIndex(childName);
	}
	
	/**
	 * returns the xpath if traversing up the tree one node
	 * i.e. /root/suspension_rec returns /root
	 * @param xpath
	 * @return
	 */
	public static final String getParentXPath(String xpath) {
		if(StringUtils.isEmpty(xpath) || xpath.lastIndexOf(SLASH) <= 0) {
			return null;
		}
		return xpath.substring(0, xpath.lastIndexOf(SLASH));
	}
	
	/**
	 * returns the index of the child element xpath
	 * i.e. /suspension_rec[3] returns 3.  /suspension_rec defaults to 1
	 * @param xpath
	 * @return 1, the index, or null if the provided xpath is empty
	 */
	public static Integer getChildElementIndex(String xpath) {
		if(StringUtils.isEmpty(xpath)) {
			return null;
		}
		
		if(xpath.endsWith(R_BRACKET)) {
			String value = xpath.substring(xpath.lastIndexOf(L_BRACKET) + 1, xpath.lastIndexOf(R_BRACKET));
			if(StringUtils.isNumeric(value)) {
				return Integer.valueOf(value);
			}
		} 
		return 1;
	}
	
	/**
	 * @param xpath
	 * @param childIndex
	 * @return
	 */
	public static String createPositionXpath(String xpath, Integer childIndex) {
		if(StringUtils.isEmpty(xpath)) {
			return null;
		}
		return stripIndex(xpath) + "[position()<" + childIndex + "]";
	}
	
	/**
	 * @param childName
	 * @return
	 */
	private static String stripIndex(String childName) {
		if(childName.endsWith(R_BRACKET)) {
			return childName.substring(0, childName.lastIndexOf(L_BRACKET));
		} else {
			return childName;
		}
	}

	

	
}

XPathUtilsTest.java

/**
 * 
 */
package com.bmchild.service.driverapp.xml;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNull;

import org.junit.Test;

/**
 * @author bchild
 *
 */
public class XPathUtilsTest {

  @Test
	public void testGetChildElementName() throws Exception {
		String childElement = XPathUtils.getChildElementName("/root/child[3]");
		assertEquals("child", childElement);
		assertNull(XPathUtils.getChildElementName(""));
		assertNull(XPathUtils.getChildElementName(null));
	}

	@Test
	public void testGetParentXPath() throws Exception {
		String parentPath = XPathUtils.getParentXPath("/root[1]/child");
		assertEquals("/root[1]", parentPath);
		assertNull(XPathUtils.getParentXPath("/root"));
		assertNull(XPathUtils.getParentXPath(""));
		assertNull(XPathUtils.getParentXPath(null));
	}

	@Test
	public void testGetChildElementIndex() throws Exception {
		Integer childIndex = XPathUtils.getChildElementIndex("/root/child[3]");
		assertEquals(new Integer(3), childIndex);
		childIndex = XPathUtils.getChildElementIndex("/root/child");
		assertEquals(new Integer(1), childIndex);
		assertNull(XPathUtils.getChildElementIndex(""));
		assertNull(XPathUtils.getChildElementIndex(null));
	}

	@Test
	public void testCreatePositionXpath() throws Exception {
		String positionXPath = XPathUtils.createPositionXpath("/root/child", 5);
		assertEquals("/root/child[position()<5]", positionXPath);
		
		positionXPath = XPathUtils.createPositionXpath("/root/anotherChild[6]", 6);
		assertEquals("/root/anotherChild[position()<6]", positionXPath);
	}

}

excellent work! really need it !

Very nice work , do you have code to address the attributes as well ?? Or can you share some highlights on this ...