beanmetadata.java

Java的面向对象数据库系统的源代码

/*
 * Copyright 2001 (C) MetaStuff, Ltd. All Rights Reserved.
 *
 * This software is open source.
 * See the bottom of this file for the licence.
 *
 * $Id: BeanMetaData.java,v 1.3 2003/11/02 18:04:59 per_nyfelt Exp $
 */

package org.dom4j.bean;

import org.dom4j.NodeFactory;
import org.dom4j.QName;

import java.beans.BeanInfo;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;

/** <p><code>BeanMetaData</code> contains metadata about a bean class.</p>
  *
  * @author <a href="mailto:[e-mail]">James Strachan</a>
  * @version $Revision: 1.3 $
  */
public class BeanMetaData {

    /** Empty arguments for reflection calls */
    protected static final Object[] NULL_ARGS = {};

    /** Singleton cache */
    private static Map singletonCache = new HashMap();

    private static final NodeFactory NODE_FACTORY = BeanDocumentFactory.getInstance();

    /** The class of the bean */
    private Class beanClass;

    /** Property descriptors for the bean */
    private PropertyDescriptor[] propertyDescriptors;

    /** QNames for the attributes */
    private QName[] qNames;

    /** Read methods used for getting properties */
    private Method[] readMethods;

    /** Write methods used for setting properties */
    private Method[] writeMethods;

    /** Index of names and QNames to indices */
    private Map nameMap = new HashMap();


    /** Static helper method to find and cache meta data objects for bean types
      */
    public static BeanMetaData get(Class beanClass) {
        BeanMetaData answer = (BeanMetaData) singletonCache.get( beanClass );
        if ( answer == null ) {
            answer = new BeanMetaData( beanClass );
            singletonCache.put( beanClass, answer );
        }
        return answer;
    }

    public BeanMetaData(Class beanClass) {
        this.beanClass = beanClass;
        if ( beanClass != null ) {
            try {
                BeanInfo beanInfo = Introspector.getBeanInfo( beanClass );
                propertyDescriptors = beanInfo.getPropertyDescriptors();
            }
            catch (IntrospectionException e) {
                handleException(e);
            }
        }
        if ( propertyDescriptors == null ) {
            propertyDescriptors = new PropertyDescriptor[0];
        }
        int size = propertyDescriptors.length;
        qNames = new QName[size];
        readMethods = new Method[size];
        writeMethods = new Method[size];
        for ( int i = 0; i < size; i++ ) {
            PropertyDescriptor propertyDescriptor = propertyDescriptors[i];
            String name = propertyDescriptor.getName();
            QName qName = NODE_FACTORY.createQName( name );
            qNames[i] = qName;
            readMethods[i] = propertyDescriptor.getReadMethod();
            writeMethods[i] = propertyDescriptor.getWriteMethod();

            Integer index = new Integer(i);
            nameMap.put( name, index );
            nameMap.put( qName, index );
        }
    }

    /** @return the number of attribtutes for this bean type
      */
    public int attributeCount() {
        return propertyDescriptors.length;
    }

    public BeanAttributeList createAttributeList(BeanElement parent) {
        return new BeanAttributeList( parent, this );
    }

    public QName getQName(int index) {
        return qNames[index];
    }

    public int getIndex(String name) {
        Integer index = (Integer) nameMap.get(name);
        return ( index != null ) ? index.intValue() : -1;
    }

    public int getIndex(QName qName) {
        Integer index = (Integer) nameMap.get(qName);
        return ( index != null ) ? index.intValue() : -1;
    }

    public Object getData(int index, Object bean) {
        try {
            Method method = readMethods[index];
            return method.invoke( bean, NULL_ARGS );
        }
        catch (Exception e) {
            handleException(e);
            return null;
        }
    }

    public void setData(int index, Object bean, Object data) {
        try {
            Method method = writeMethods[index];
            Object[] args = { data };
            method.invoke( bean, args );
        }
        catch (Exception e) {
            handleException(e);
        }
    }

    // Implementation methods
    //-------------------------------------------------------------------------
    protected void handleException(Exception e) {
        // ignore introspection exceptions
    }
}




/*
 * Redistribution and use of this software and associated documentation
 * ("Software"), with or without modification, are permitted provided
 * that the following conditions are met:
 *
 * 1. Redistributions of source code must retain copyright
 *    statements and notices.  Redistributions must also contain a
 *    copy of this document.
 *
 * 2. Redistributions in binary form must reproduce the
 *    above copyright notice, this list of conditions and the
 *    following disclaimer in the documentation and/or other
 *    materials provided with the distribution.
 *
 * 3. The name "DOM4J" must not be used to endorse or promote
 *    products derived from this Software without prior written
 *    permission of MetaStuff, Ltd.  For written permission,
 *    please contact [e-mail].
 *
 * 4. Products derived from this Software may not be called "DOM4J"
 *    nor may "DOM4J" appear in their names without prior written
 *    permission of MetaStuff, Ltd. DOM4J is a registered
 *    trademark of MetaStuff, Ltd.
 *
 * 5. Due credit should be given to the DOM4J Project
 *    (http://dom4j.org/).
 *
 * THIS SOFTWARE IS PROVIDED BY METASTUFF, LTD. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
 * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
 * METASTUFF, LTD. OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Copyright 2001 (C) MetaStuff, Ltd. All Rights Reserved.
 *
 * $Id: BeanMetaData.java,v 1.3 2003/11/02 18:04:59 per_nyfelt Exp $
 */