object2xml.java

用Java写的面相对象的数据库管理系统

// You can redistribute this software and/or modify it under the terms of
// the Ozone Core License version 1 published by ozone-db.org.
//
// The original code and portions created by SMB are
// Copyright (C) 1997-2000 by SMB GmbH. All rights reserved.
//
// $Id: Object2XML.java,v 1.6 2000/10/28 16:55:19 daniela Exp $

package org.ozoneDB.core.xml;

import java.util.*;
import java.io.*;
import java.lang.reflect.*;

import org.xml.sax.*;
import org.xml.sax.helpers.*;

import org.ozoneDB.core.ObjectContainer;
import org.ozoneDB.OzoneInterface;


/**
 * This class transform an Object into XML.
 * 
 * @version $Revision: 1.6 $
 * @author <a href="http://www.softwarebuero.de">SMB</a>
 */


public class Object2XML implements Consts {
    
    //
    // member
    //
    
    /**
     * ObjCache saves the references of the processed objects.
     */
    private Hashtable objCache = new Hashtable();
    
    /**
     * This flag decides if transient member will be serialized or not.
     */
    private boolean serializeTransientFlag = false;
    
    /**
     * ... for making SAX.
     */
    private ContentHandler ch;
    
    /**
     * Factory for the attributes of the first obj-Tag.
     */
    private ObjAttsFactory oaf;
    
    
    //
    // construcor
    //
    
    
    /**
     * @param docHandler
     */
    public Object2XML( ContentHandler contHandler ) {
        ch = contHandler;
        oaf = new OzoneObjAttsFactory();
    }
    
    
    /**
     * @param docHandler
     * @param serializeTransientFlag
     */
    public Object2XML( ContentHandler contHandler, boolean serializeTransientFlag ) {
        this( contHandler );
        this.serializeTransientFlag = serializeTransientFlag;
    }
    
    //
    // methods
    //
    
    
    /**
     * ToXML(obj) gets an object and serialize this object into XML.
     *
     * @param obj (the Object)
     */
    public void toXML( Object obj ) throws SAXException {
        ch.startDocument();
        writeObjStartTag( obj.getClass().getName(), getID( obj ), oaf.additionallyAtts( obj ) );
        objCache.put( getID( obj ), getID( obj ) );
        
        getMember( obj, obj.getClass() );
        
        writeObjEndTag();
        ch.endDocument();
    } 
    
    
    /**
     * GetMember gets the informations (name/type/value)
     * of all members (private and protected too) !!
     *
     * @param obj (the Object)
     * @param objClass (the Class of the Object)
     */
    protected void getMember( Object obj, Class objClass ) throws SAXException {
        // System.out.println ("getMember(): " + obj.getClass().getName() + ", " + objClass.getName());
        
        Field[] fds = objClass.getDeclaredFields();
        AccessibleObject.setAccessible( fds, true );
        for (int i = 0; i < fds.length; i++) {
            Field fd = fds[i];
            
            // avoid converting the container of a database object
            if (ObjectContainer.class.isAssignableFrom( fd.getType() )) {
                continue;
            } 
            if (OzoneInterface.class.isAssignableFrom( fd.getType() )) {
                continue;
            } 
            if (Modifier.isStatic( fd.getModifiers() )) {
                continue;
            } 
            if (!serializeTransientFlag && Modifier.isTransient( fd.getModifiers() )) {
                continue;
            } 
            
            String memberName = fd.getName();
            writeMemberStartTag( memberName );
            
            try {
                
                Object value = fd.get( obj );
                getValue( value );
            
            } catch (IllegalAccessException iae) {
                System.err.println( "(getMember) EXCEPTION: " + iae );
            } 
            writeMemberEndTag();
        } 
        
        superClass( obj, objClass );
    } 
    
    
    /**
     * SuperClass gets the informations about the Superclass of the Object.
     *
     * @param obj (the Object)
     * @param objClass (the Class of the Object)
     */
    private void superClass( Object obj, Class objClass ) throws SAXException {
        
        Class superClass = objClass.getSuperclass();
        if (superClass == null) {
            return;
        } 
        
        writeSuperClStartTag( superClass.getName() );
        
        getMember( obj, superClass );
        writeSuperClEndTag();
    } 
    
    
    /**
     * GetValue gets the value of the certain member.
     *
     * @param value (value of the member)
     */
    protected void getValue( Object value ) throws SAXException {
        if (value == null) {
            return;
        } 
        
        getValue( value, value.getClass() );
    } 
    
    
    /**
     * GetValue gets the value of the certain member.
     *
     * @param value (value of the member)
     * @param valueType (the Class of the certainMember)
     */
    protected void getValue( Object value, Class valueType ) throws SAXException {
        if (value == null) {
            return;
        } 
        
        if (valueType.isPrimitive() || value instanceof Boolean || value instanceof Byte || value instanceof Character 
                || value instanceof Double || value instanceof Float || value instanceof Long 
                || value instanceof Integer || value instanceof Short || value instanceof String) {
            
            if (valueType.isPrimitive()) {
                writeValueStartTag( valueType.getName(), getID( value ) );
            } else {
                if (objCache.containsKey( getID( value ) )) {
                    writeObjRefElement( getID( value ) );
                    return;
                } 
                writeValueStartTag( value.getClass().getName(), getID( value ) );
                objCache.put( getID( value ), getID( value ) );
            } 
            
            writeValue( value.toString() );
            writeValueEndTag();
            
            return;
        } 
        
        
        if (objCache.containsKey( getID( value ) )) {
            writeObjRefElement( getID( value ) );
            return;
        } 
        
        
        if (valueType.isArray() && value != null) {
            int length = Array.getLength( value );
            Class subType = value.getClass().getComponentType();
            writeArrayStartTag( valueType.getName(), getID( value ) );
            objCache.put( getID( value ), getID( value ) );
            for (int l = 0; l < length; l++) {
                Object subValue = Array.get( value, l );
                
                if (subType.isPrimitive()) {
                    getValue( subValue, subType );
                } else {
                    getValue( subValue );
                } 
            } 
            writeArrayEndTag();
        
        } else {
            if (value != null) {
                writeValueObjStartTag( value.getClass().getName(), getID( value ) );
                objCache.put( getID( value ), getID( value ) );
                
                getMember( value, value.getClass() );
                writeValueObjEndTag();
            } 
        } 
    } 
    
    
    /**
     * GetId gets the reference/address of the Object.
     *
     * @param obj (the Object)
     * @return id
     */
    protected Integer getID( Object obj ) {
        Integer id = new Integer( System.identityHashCode( obj ) );
        return id;
    } 
    
    
    //
    // writeMethods
    // The writeMethods helps to write XML/SAX.
    //
    protected void writeObjStartTag( String classname, Integer id, Attributes additionallyAtts ) throws SAXException {
        
        AttributesImpl atts;
        if (additionallyAtts != null) {
            atts = new AttributesImpl( additionallyAtts );
        } else {
            atts = new AttributesImpl();
        } 
        
        atts.addAttribute( "", ATTR_TYPE, ATTR_TYPE, "String", classname );
        atts.addAttribute( "", ATTR_ID, ATTR_ID, "Integer", id + "" );
        
        ch.startElement( "", TAG_OBJ, TAG_OBJ, atts );
    } 
    
    
    protected void writeObjEndTag() throws SAXException {
        ch.endElement( "", TAG_OBJ, TAG_OBJ );
    } 
    
    
    protected void writeSuperClStartTag( String classname ) throws SAXException {
        AttributesImpl atts = new AttributesImpl();
        atts.addAttribute( "", ATTR_TYPE, ATTR_TYPE, "String", classname );
        
        ch.startElement( "", TAG_SUPERCLASS, TAG_SUPERCLASS, atts );
    } 
    
    
    protected void writeSuperClEndTag() throws SAXException {
        ch.endElement( "", TAG_SUPERCLASS, TAG_SUPERCLASS );
    } 
    
    
    protected void writeMemberStartTag( String name ) throws SAXException {
        AttributesImpl atts = new AttributesImpl();
        atts.addAttribute( "", ATTR_NAME, ATTR_NAME, "String", name );
        
        ch.startElement( "", TAG_MEMBER, TAG_MEMBER, atts );
    } 
    
    
    protected void writeMemberEndTag() throws SAXException {
        ch.endElement( "", TAG_MEMBER, TAG_MEMBER );
    } 
    
    
    protected void writeValue( String value ) throws SAXException {
        ch.characters( value.toCharArray(), 0, value.length() );
    } 
    
    
    protected void writeValueStartTag( String type, Integer id ) throws SAXException {
        AttributesImpl atts = new AttributesImpl();
        atts.addAttribute( "", ATTR_TYPE, ATTR_TYPE, "String", type );
        atts.addAttribute( "", ATTR_ID, ATTR_ID, "Integer", id + "" );
        
        ch.startElement( "", TAG_VALUE, TAG_VALUE, atts );
    } 
    
    
    protected void writeValueEndTag() throws SAXException {
        ch.endElement( "", TAG_VALUE, TAG_VALUE );
    } 
    
    
    protected void writeValueObjStartTag( String type, Integer id ) throws SAXException {
        AttributesImpl atts = new AttributesImpl();
        atts.addAttribute( "", ATTR_TYPE, ATTR_TYPE, "String", type );
        atts.addAttribute( "", ATTR_ID, ATTR_ID, "Integer", id + "" );
        
        ch.startElement( "", TAG_VALUEOBJ, TAG_VALUEOBJ, atts );
    } 
    
    
    protected void writeValueObjEndTag() throws SAXException {
        ch.endElement( "", TAG_VALUEOBJ, TAG_VALUEOBJ );
    } 
    
    
    protected void writeArrayStartTag( String type, Integer id ) throws SAXException {
        AttributesImpl atts = new AttributesImpl();
        atts.addAttribute( "", ATTR_TYPE, ATTR_TYPE, "String", type );
        atts.addAttribute( "", ATTR_ID, ATTR_ID, "Integer", id + "" );
        
        ch.startElement( "", TAG_VALUEARRAY, TAG_VALUEARRAY, atts );
    } 
    
    
    protected void writeArrayEndTag() throws SAXException {
        ch.endElement( "", TAG_VALUEARRAY, TAG_VALUEARRAY );
    } 
    
    
    protected void writeObjRefElement( Integer sourceId ) throws SAXException {
        AttributesImpl atts = new AttributesImpl();
        atts.addAttribute( "", ATTR_REF, ATTR_REF, "Integer", sourceId + "" );
        
        ch.startElement( "", TAG_VALUE, TAG_VALUE, atts );
        ch.endElement( "", TAG_VALUE, TAG_VALUE );
    } 
}