xmlbeaninfo.java

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/*
 * Copyright 2001-2004 The Apache Software Foundation.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */ 
package org.apache.commons.betwixt;

/** <p><code>XMLBeanInfo</code> represents the XML metadata information
  * used to map a Java Bean cleanly to XML. This provides a default
  * introspection mechansim, rather like {@link java.beans.BeanInfo} 
  * which can be customized through some mechansim, either via Java code 
  * or XSLT for example.</p>
  *
  * <h4><code>ID</code> and <code>IDREF</code> Attribute Names</h4>
  * <p>These special attributes are defined in the xml specification.
  * They are used by Betwixt to write bean graphs with cyclic references.
  * In most cases, these will take the values 'id' and 'idref' respectively 
  * but these names can be varied in the DTD.
  * Therefore, these names are specified by this class but default to the
  * usual values.</p>
  *
  * @author <a href="mailto:[e-mail]">James Strachan</a>
  * @version $Revision: 1.9 $
  */
public class XMLBeanInfo {
    /** Descriptor for main element */
    private ElementDescriptor elementDescriptor;
    
    /** the beans class that this XML info refers to */
    private Class beanClass;
    /** <code>ID</code> attribute name */
    private String idAttributeName = "id";
    /** <code>IDREF</code> attribute name */
    private String idrefAttributeName = "idref";
    /** Have we already cached the <code>idAttributeDescriptor</code>? */
    private boolean cachedIDAttribute = false;
    /** Cached <code>ID</code> attribute descriptor */
    private AttributeDescriptor idAttributeDescriptor;
    
    /** 
     * Base constructor 
     * @param beanClass for this Class
     */
    public XMLBeanInfo( Class beanClass ) {
        this.beanClass = beanClass;        
    }

    /** 
     * Gets descriptor for bean represention 
     *
     * @return ElementDescriptor describing root element
     */
    public ElementDescriptor getElementDescriptor() {
        return elementDescriptor;
    }

    /** 
     * Sets descriptor for bean represention 
     *
     * @param elementDescriptor descriptor for bean
     */
    public void setElementDescriptor(ElementDescriptor elementDescriptor) {
        this.elementDescriptor = elementDescriptor;
    }    
    
    /**  
     * Gets the beans class that this XML info refers to
     *
     * @return the beans class that this XML info refers to 
     */
    public Class getBeanClass() {
        return beanClass;
    }
    
    /** 
     * Sets the beans class that this XML info refers to 
     *
     * @param beanClass the class that this refers to
     */
    public void setBeanClass(Class beanClass) {
        this.beanClass = beanClass;
    }
    
    /** 
     * Search attributes for one matching <code>ID</code> attribute name 
     *
     * @return the xml ID attribute
     */
    public AttributeDescriptor getIDAttribute() {
        //
        // XXX for some reason caching isn't working at the moment
        // it could be that this method is called too early
        // and not reset when attributes change
        // on the other hand, the speed gain is likely to be too
        // small to bother about
        //
        //if ( cachedIDAttribute = false ) {
            idAttributeDescriptor = findIDAttribute();
          //  cachedIDAttribute = true;
        //}
        return idAttributeDescriptor;
    }
    
    /** 
     * ID attribute search implementation 
     * @return the AttributeDescriptor for the <code>ID</code> attribute
     */
    private AttributeDescriptor findIDAttribute() {
        // we'll check to see if the bean already has an id
        if ( getElementDescriptor().hasAttributes() ) {
            AttributeDescriptor[] attributes = getElementDescriptor().getAttributeDescriptors();
            if ( attributes != null ) {
                for ( int i = 0, size = attributes.length; i < size; i++ ) {
                    // support a match either on local or qualified name
                    if ( getIDAttributeName().equals( attributes[i].getQualifiedName() ) 
                        || getIDAttributeName().equals( attributes[i].getLocalName() )) {
                        // we've got a match so use this attribute
                        return attributes[i];
                        
                    }
                }
            }
        }
        return null;
    }
    
    /** 
      * <p>Get name of <code>ID</code> attribute.
      * This is used to write (for example) automatic <code>ID</code>
      * attribute values.</p>
      * 
      * <p>The default name is 'id'.</p>
      *
      * @return name for the special <code>ID</code> attribute
      */
    public String getIDAttributeName() {
        return idAttributeName;
    }
    
    /** 
      * Set name of <code>ID</code> attribute 
      * This is used to write (for example) automatic <code>ID</code>
      * attribute values.</p>
      * 
      * <p>The default name is 'id'.</p>
      *
      * @param idAttributeName the attribute name for the special <code>ID</code> attribute
      */
    public void setIDAttributeName(String idAttributeName) {
        this.idAttributeName = idAttributeName;
    }
    
    /** 
      * <p>Get <code>IDREF</code> attribute name 
      * This is used (for example) to deal with cyclic references.
      *
      * <p>The default name is 'idref'.</p>
      *
      * @return name for the special <code>IDREF</code> attribute
      */
    public String getIDREFAttributeName() {
        return idrefAttributeName;
    }
    
    /** 
      * Set <code>IDREF</code> attribute name 
      * This is used (for example) to deal with cyclic references.
      *
      * <p>The default name is 'idref'.</p>
      *
      * @param idrefAttributeName the attribute name for the special <code>IDREF</code> attribute
      */
    public void setIDREFAttributeName(String idrefAttributeName) {
        this.idrefAttributeName = idrefAttributeName;
    }
    
    /**
     * Gets log-friendly string representation.
     *
     * @return something useful for logging
     */
    public String toString() {
        return 
                "XMLBeanInfo [class=" + getBeanClass() 
                + ", descriptor=" + getElementDescriptor() + "]";
    }
}