package com.javaranch.dynadto;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.Map;
import org.apache.commons.beanutils.BasicDynaClass;
import org.apache.commons.beanutils.DynaBean;
import org.apache.commons.beanutils.DynaClass;
import org.apache.commons.digester.Digester;
import org.xml.sax.SAXException;

/**
 * <p>A class that makes new instances of Dynamic Data Transfer Objects (DTO).
 * The DTOs are implementations of <tt>org.apache.commons.beanutils.DynaBean</tt>.
 * The DTOS and their properties are specified in an xml configuration file.</p>
 *
 * <p>The default name of the configuration file is "dto-config.xml", and should
 * reside somewhere in the classpath.  The configuration file is validated
 * with "dynaDTO.dtd", which can be found in this package, and must point to the
 * location of this DTD.</p>
 *
 * <p>An example "dto-config.xml" file:</p>
 *
 * <p><pre>
 * &lt;?xml version="1.0" encoding="ISO-8859-1"?&gt;
 * &lt;!DOCTYPE dto-config SYSTEM "file://C/dynaDTO/dynaDTO.dtd"&gt;
 * &lt;dto-config&gt;
 *   &lt;dto name="book" type="org.apache.commons.beanutils.BasicDynaBean"&gt;
 *     &lt;property name="title" type="java.lang.String"/&gt;
 *     &lt;property name="isbn" type="java.lang.String"/&gt;
 *   &lt;/dto&gt;
 *   &lt;dto name="author"&gt;
 *     &lt;property name="firstName" type="java.lang.String"/&gt;
 *     &lt;property name="lastName" type="java.lang.String"/&gt;
 *   &lt;/dto&gt;
 * &lt;/dto-config&gt;
 * </pre></p>
 *
 * <p>Each &lt;dto&gt; element represents a different Data Transfer Object.
 * The <i>name</i> attribute of the &lt;dto&gt; element indicates the name of
 * the DTO which will be used when calling <tt>newInstance()</tt>.  The
 * <i>type</i> attribute of the &lt;dto&gt; element is the class type
 * instantiated by a call to <tt>newInstance()</tt>, and must be a class which
 * implements the <tt>org.apache.commons.beanutils.DynaBean</tt> interface.
 * The <i>type</i> attribute is optional, with DTOs of type
 * <tt>com.javaranch.dynadto.DynaDTODynaBean</tt> being instantiated if
 * no <i>type</i> is specified.</p>
 *
 * <p>The properties of each DTO are specified with &lt;property&gt; elements.
 * The name of each property is indicated by the <i>name</i> attribute, and the
 * type of each property is indicated by the <i>type</i> attribute.  Both of
 * these attributes are required.</p>
 *
 * <p>As has already been mentioned, DTOs are instantiated by a call to the
 * <tt>newInstance()</tt> method of the <tt>DynaDTOFactory</tt> class.  If the
 * above "dto-config.xml" file were used, we could retrieve and use a new
 * instance of a <i>book</i> DTO in the following manner:</p>
 *
 * <p><pre>
 * DynaDTOFactory factory = new DynaDTOFactory();
 * DynaBean book = factory.newInstance("book");
 * book.set("title", "War and Peace");
 * String title = (String) book.get("title");
 * </pre></p>
 *
 * @author Jason Menard
 * @version 1.0
 */
public class DynaDTOFactory {

    /*
     * The set of DynaClass objects that are part of this factory,
     * keyed by the name of the DynaBean associated with each DynaClass.
     */
    private Map dynaClassMap = new HashMap();

    /* Default file name for the config file. */
    private String config = "dto-config.xml";

    /**
     * Constructs a new DynaDTOFactory with default parameters.
     * @throws FileNotFoundException
     * @throws IOException
     * @throws SAXException
     */
    public DynaDTOFactory() throws FileNotFoundException,
                                   IOException,
                                   SAXException {
        init();
    }

    /**
     * Constructs a new DynaDTOFactory with the specified parameters.
     * @param config the name of the configuration file to use with this
     * instance
     * @throws FileNotFoundException
     * @throws IOException
     * @throws SAXException
     */
    public DynaDTOFactory(String config) throws FileNotFoundException,
                                                IOException,
                                                SAXException {
        this.config = config;
        init();
    }

    /**
     * Instantiate a new instance of the specified DynaDTO
     * @param name the name of the DynaDTO to return
     * @return a new instance of the DynaDTO specified
     * @throws java.lang.InstantiationException
     * @throws java.lang.IllegalAccessException
     */
    public DynaBean newInstance(String name) throws InstantiationException,
                                                    IllegalAccessException {
        DynaBean dynaBean = null;
        DynaClass dynaClass = (DynaClass) dynaClassMap.get(name);
        if (dynaClass != null) {
            dynaBean = dynaClass.newInstance();
        }
        return dynaBean;
    }

    /**
     * Add a DynaClass to the DynaDTOFactory
     * @param dynaClass the DynaClass to add to this factory
     */
    void addDynaClass(DynaClass dynaClass) {
        dynaClassMap.put(dynaClass.getName(), dynaClass);
    }

    /* Initialize the DynaDTOFactory by digesting the config file */
    private void init() throws FileNotFoundException,
                               IOException,
                               SAXException {
        InputStream is =
            Thread.currentThread().getContextClassLoader().getResourceAsStream(config);
        if (is == null) {
            throw new FileNotFoundException(config + " file not found.");
        }
        Digester digester = new Digester();
        digester.setNamespaceAware(true);
        digester.setValidating(true);
        digester.setUseContextClassLoader(true);
        digester.addRuleSet(new DynaDTORuleSet());
        digester.push(this);
        digester.parse(is);
        is.close();
    }

    public static void main(String[] args) {
        try {
            DynaDTOFactory ddf = null;
            ddf = new DynaDTOFactory();
            DynaDTODynaBean program = (DynaDTODynaBean)ddf.newInstance("program");
            program.set("name", "KIV-7");
            System.out.println(program.get("name"));
            System.out.println(program);
        }
        catch (Exception e) {
            e.printStackTrace();
        }
    }
}