package com.javaworld.JavaBeans.XMLBeans;


import java.io.*;
import java.beans.*;
import org.w3c.dom.*;
import com.ibm.xml.parser.*;
import java.lang.reflect.*;

/**
 * This class contains static methods that write a JavaBean
 * to a Writer object, formatted as XML.
 */
public class XMLBeanWriter {

/**
 * Constructor is, for the most part, superfluous, since all
 * of the object's methods are <B>static</B>.
 */
public XMLBeanWriter() {
	super();
}
/**
 * Build a DOM DocumentFragment representing the class and properties of
 * a JavaBean.
 * @return org.w3c.dom.DocumentFragment - the document representing the JavaBean.
 * @param doc Creates nodes using this document as a factory.
 * @param bean The JavaBean for which we want the DOM tree
 * @exception java.beans.IntrospectionException An error occurred during
 * introspection of the JavaBean.
 */
public static DocumentFragment getAsDOM(Document doc, Object bean) throws IntrospectionException, InstantiationException, IllegalAccessException {

	// Create the fragment we'll return
	DocumentFragment dfResult = null;

	// Analyze the bean
	Class classOfBean = bean.getClass();

	// If the bean knows how to encode itself in XML, then
	// use the DOM document it returns.
	try {
		Method mgetAsDOM = classOfBean.getMethod("getAsDOM",
				new Class[] { org.w3c.dom.Document.class } );
		dfResult = (DocumentFragment) mgetAsDOM.invoke(bean,
				new Object[] { doc });
	} catch (Exception e) {
		; // Ignore exceptions
	}

	// If the bean doesn't know how to encode itself in XML,
	// then create a DOM document by introspecting it.
	if (dfResult == null) {
		dfResult = doc.createDocumentFragment();
		BeanInfo bi = Introspector.getBeanInfo(classOfBean);
		PropertyDescriptor[] pds = bi.getPropertyDescriptors();

		// Add an Element indicating that this is a JavaBean.
		// The element has a single attribute, which is that Element's class.
		Element eBean = doc.createElement("JavaBean");
		dfResult.appendChild(eBean);
		eBean.setAttribute("CLASS", classOfBean.getName());
		Element eProperties = doc.createElement("Properties");
		eBean.appendChild(eProperties);

		// For each property of the bean, get a DocumentFragment that
		// represents the individual property. Append that DocumentFragment
		// to the Properties element of the document
		for (int i = 0; i < pds.length; i++) {
			PropertyDescriptor pd = pds[i];
			DocumentFragment df = getAsDOM(doc, bean, pd);
			if (df != null) {
				// Create a Property element and add to Properties element
				Element eProperty = doc.createElement("Property");
				eProperties.appendChild(eProperty);

				// Create NAME attribute, add it to Property element,
				// and set it to name of property
				eProperty.setAttribute("NAME", pd.getName());

				// Append the DocumentFragment to the Property element
				// This "splices" the entire DOM representation of the
				// Property into the tree at this point.
				eProperty.appendChild(df);
			}
		}
	}
	return dfResult;
}
/**
 * Return a DOM DocumentFragment representing a property of a JavaBean
 * @return org.w3c.dom.DocumentFragment
 * @param doc The document to use as a factory for
 * subelements of the tree.
 * @param bean The object that is the value of the property.
 * This object must be a JavaBean.
 * @param pd A property descriptor describing
 * the property of which the object is a value.
 * @exception IllegalAccessException
 * @exception InstantiationException
 * @exception IntrospectionException
 */
public static DocumentFragment getAsDOM(Document doc, Object bean, PropertyDescriptor pd) throws IntrospectionException, InstantiationException, IllegalAccessException {
	Class classOfBean = bean.getClass();
	Class classOfProperty = pd.getPropertyType();
	DocumentFragment dfResult = null;
	String sValueAsText = null;
	Class[] paramsNone = {};
	Object[] argsNone = {};

	// If the property is "class", and the type is java.lang.class, then
	// this is the class of the bean, which we've already encoded.
	// So, in this special case, return null.
	if (pd.getName().equals("class") && classOfProperty.equals(java.lang.Class.class)) {
		return null;
	}

	// 1. Try to represent the property as XML.
	// This bean may know how to describe itself, or parts of
	// itself, as XML. There are two possibilities:
	// [a] The bean has a method called get<Propname>AsXML()
	// [b] The property class has a method called getAsDOM()
	// We'll try both of these, and the first (if any) that
	// works will be the DocumentFragment we want to return.
	// If none of these are true, then we try to find the object's
	// value as text

	// [1a] Does the bean have a method called get<Propname>AsXML()?
	// Capitalize property name
	StringBuffer sPropname = new StringBuffer(pd.getName());
	char c = sPropname.charAt(0);
	if (c >= 'a' && c <= 'z') {
		c += 'A' - 'a';
	}
	sPropname.setCharAt(0, c);
	String sXMLGetterName = "get" + sPropname + "AsXML";

	// If both of these methods succeed, then dfResult will be set
	// to non-null; that is, the method existed and returned a
	// DocumentFragment
	try {
		Class [] params = { org.w3c.dom.Document.class };
		Method mXMLGetter = classOfBean.getMethod(sXMLGetterName, params);
		Object[] args = { doc };
		dfResult = (DocumentFragment) (mXMLGetter.invoke(bean, args));
	} catch (Exception ee) {
		; // Ignore... couldn't get the method
	}

	// Hereafter, we're trying to create a representation of the property
	// based somehow on the property's value.
	// The very first thing we need to do is get the value of the
	// property as an object. If we can't do that, we can get no
	// representation of the property at all.
	Object oPropertyValue = null;
	try {
		Method getter = pd.getReadMethod();
		if (getter != null) {
			oPropertyValue = getter.invoke(bean, argsNone);
		}
	} catch (InvocationTargetException ex) {
		; // Couldn't get value. Probably should be an error.
	}

	// [1b] If we don't have a DocumentFragment, the previous block failed.
	// So, let's find out if the property's class has a method called
	// getAsDOM() and, if it does, call that instead.
	if (dfResult == null) {
		try {
			Class [] params = { org.w3c.dom.Document.class };
			Method mXMLGetter = classOfProperty.getMethod("getAsDOM", params);
			Object[] args = { doc };
			dfResult = (DocumentFragment) (mXMLGetter.invoke(oPropertyValue, args));
		} catch (Exception ee) {
			; // Ignore -- who cares why it failed?
		}
	}


	// 2. Try to represent the property as a String.
	// See if this property's value
	// is something we can represent as Text, or if it's something
	// that must be represented as a JavaBean. Let's assume that this
	// object can be represented as text if:
	// [a] it has a PropertyEditor associated with it, because
	// PropertyEditors always have setAsText() and getAsText()
	// If it can't be represented as text, then we pass it to
	// getAsDOM(Document, Object) and return the result.

	if (dfResult == null) {

		// [2a] Can we get either a custom or built-in property editor?
		// If the PropertyDescriptor returns an editor class, we
		// create an instance of it; otherwise, we ask the system for
		// a default editor for that class.
		Class pedClass = pd.getPropertyEditorClass();
		PropertyEditor propEditor = null;
		if (pedClass != null) {
			propEditor = (PropertyEditor) (pedClass.newInstance());
		} else {
			propEditor = PropertyEditorManager.findEditor(classOfProperty);
		}

		// If the property editor's not null, pass the property's
		// value to the PropertyEditor, and then ask the PropertyEditor
		// for a text representation of the object.
		if (propEditor != null) {
			propEditor.setValue(oPropertyValue);
			sValueAsText = propEditor.getAsText();
		}

		// If somewhere above we found a string value, then create
		// a DocumentFragment to return, and append to it
		// a Text element.
		if (sValueAsText != null) {
			dfResult = doc.createDocumentFragment();
			Text textValue = doc.createTextNode(sValueAsText);
			dfResult.appendChild(textValue);
		}
	}

	// 3. Try to represent the property value as a JavaBean
	// If we don't have a DocumentFragment yet, we'll
	// have to introspect the value of the object, because
	// it's apparently something that can't be represented
	// as flat text. We'll assume it's a JavaBean.
	// If it isn't... oh, well.
	//
	if (dfResult == null) {
		dfResult = getAsDOM(doc, oPropertyValue);
	}
	return dfResult;
}
/**
 * This main method tests XMLBeanWriter.writeXMLBean() by loading
 * an JavaBean from the file whose name appears as the first argument
 * on the command line.
 * @param args java.lang.String[]
 */
public static void main(String args[]) {
	Object b = null;
	try {
		b = XMLBeanReader.readXMLBean(args[0]);
		try {
			Method printer = b.getClass().getMethod("print", null);
			P("--- Read a JavaBean of type " + b.getClass().getName());
			printer.invoke(b, null);
		} catch (Exception ee) {
			P("Unable to print JavaBean");
		}
	} catch (Exception ee) {
		P("Couldn't read JavaBean from file " + args[0]);
		ee.printStackTrace();
	}

	// Now, write it back out
	if (b != null && args.length > 1) {
		try {
			XMLBeanWriter.writeXMLBean(b, args[1]);
		} catch (Exception ee) {
			P("Couldn't write JavaBean to file " + args[1]);
			ee.printStackTrace();
		}
	}
}
/**
 * Shorthand method to print to stdout.
 * @param s The string to print
 */
static public void p(String s) {
	XMLBeanReader.p(s);
}
/**
 * Shorthand method to print to stdout, with a newline appended.
 * @param s The string to print
 */
static public void P(String s) {
	XMLBeanReader.P(s);
}
/**
 * Write a JavaBean as XML to a File. 
 * @param bean The JavaBean to write
 * @param file The File to which to write the JavaBean.
 * @exception java.io.FileNotFoundException
 * @exception java.beans.IntrospectionException
 */
public static void writeXMLBean(Object bean, File file) throws java.io.IOException, java.beans.IntrospectionException,
InstantiationException, IllegalAccessException {
	writeXMLBean(bean, new FileWriter(file));
}


/**
 * Write a JavaBean as XML to a Writer. 
 * @param bean The JavaBean to write.
 * @param writer The writer to which the XML is written.
 * @exception java.beans.IntrospectionException
 * @exception IOException
 * @exception InstantiationException
 * @exception IllegalAccessException
 */
public static void writeXMLBean(Object bean, Writer writer) throws IOException,
java.beans.IntrospectionException,
InstantiationException, IllegalAccessException {
	// Create a DOM document tree for this JavaBean and return it
	// NOTE: This method specifically references TXDocument,
	// which is an xml4j class!
	TXDocument doc = new TXDocument();
	DocumentFragment df = getAsDOM(doc, bean);
	doc.appendChild(df);

	// Write out the document as XML to the Writer.
	// NOTE AGAIN: Specifically references TXDocument.printWithFormat(),
	// which is xml4j-specific!
	doc.printWithFormat(writer);

}
/**
 * Write a JavaBean, formatted as XML, to a file whose name is passed as <b>sFilename</b>.
 * @param bean The JavaBean to write
 * @param sFilename The name or path to the file to write.
 * @exception java.io.FileNotFoundException 
 * @exception java.beans.IntrospectionException 
 */
public static void writeXMLBean(Object bean, String sFilename) throws java.io.IOException, java.beans.IntrospectionException,
InstantiationException, IllegalAccessException {
	writeXMLBean(bean, new FileWriter(sFilename));
}
}