beanbindaction.java

JAVA 文章管理系统源码

/*
 * Copyright 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.io.read;

import java.util.Map;

import org.apache.commons.betwixt.AttributeDescriptor;
import org.apache.commons.betwixt.ElementDescriptor;
import org.apache.commons.betwixt.TextDescriptor;
import org.apache.commons.betwixt.XMLBeanInfo;
import org.apache.commons.betwixt.expression.Updater;
import org.apache.commons.logging.Log;
import org.xml.sax.Attributes;

/**
 * Action that creates and binds a new bean instance.
 * 
 * @author <a href='http://jakarta.apache.org/'>Jakarta Commons Team</a>
 * @version $Revision: 1.2 $
 */
public class BeanBindAction extends MappingAction.Base {

    /** Singleton instance */
    public static final BeanBindAction INSTANCE = new BeanBindAction();

    /**
     * Begins a new element which is to be bound to a bean.
     */
    public MappingAction begin(
        String namespace,
        String name,
        Attributes attributes,
        ReadContext context)
                    throws Exception {
                        
        Log log = context.getLog();

        ElementDescriptor computedDescriptor = context.getCurrentDescriptor();

        if (log.isTraceEnabled()) {
            log.trace("Element Pushed: " + name);
        }

        // default to ignoring the current element
        MappingAction action = MappingAction.EMPTY;

        Object instance = null;
        Class beanClass = null;
        if (computedDescriptor == null) {
            log.trace("No Descriptor");
        } else {
            beanClass = computedDescriptor.getSingularPropertyType();
        }
        // TODO: this is a bit of a workaround 
        // need to come up with a better way of doing maps
        if (beanClass != null && !Map.class.isAssignableFrom(beanClass)) {

            instance =
                createBean(
                    namespace,
                    name,
                    attributes,
                    computedDescriptor,
                    context);
                    
            if (instance != null) {
                action = this;
                context.markClassMap(beanClass);

                if (log.isTraceEnabled()) {
                    log.trace("Marked: " + beanClass);
                }

                context.pushBean(instance);

                // if we are a reference to a type we should lookup the original
                // as this ElementDescriptor will be 'hollow' 
                // and have no child attributes/elements.
                // XXX: this should probably be done by the NodeDescriptors...
                ElementDescriptor typeDescriptor =
                    getElementDescriptor(computedDescriptor, context);
                //ElementDescriptor typeDescriptor = descriptor;

                // iterate through all attributes        
                AttributeDescriptor[] attributeDescriptors =
                    typeDescriptor.getAttributeDescriptors();
                context.populateAttributes(attributeDescriptors, attributes);

                if (log.isTraceEnabled()) {
                    log.trace("Created bean " + instance);
                }

                // add bean for ID matching
                if (context.getMapIDs()) {
                    // XXX need to support custom ID attribute names
                    // XXX i have a feeling that the current mechanism might need to change
                    // XXX so i'm leaving this till later
                    String id = attributes.getValue("id");
                    if (id != null) {
                        context.putBean(id, instance);
                    }
                }
            }
        }
        return action;
    }


    public void body(String text, ReadContext context) throws Exception {
        Log log = context.getLog();
        // Take the first content descriptor
        ElementDescriptor currentDescriptor = context.getCurrentDescriptor();
        if (currentDescriptor == null) {
            if (log.isTraceEnabled()) {
                log.trace("path descriptor is null:");
            }
        } else {
            TextDescriptor bodyTextdescriptor =
                currentDescriptor.getPrimaryBodyTextDescriptor();
            if (bodyTextdescriptor != null) {
                if (log.isTraceEnabled()) {
                    log.trace("Setting mixed content for:");
                    log.trace(bodyTextdescriptor);
                }
                Updater updater = bodyTextdescriptor.getUpdater();
                if (log.isTraceEnabled())
                {    
                    log.trace("Updating mixed content with:");
                    log.trace(updater);
                }
                if (updater != null && text != null) {
                    updater.update(context, text);
                }
            }
        }
    }

    public void end(ReadContext context) throws Exception {
        // force any setters of the parent bean to be called for this new bean instance
        Object instance = context.popBean();
        update(context, instance);
    }

    private void update(ReadContext context, Object value) throws Exception {
        Log log = context.getLog();

        Updater updater = context.getCurrentUpdater();
        
        if ( updater == null ) {
            if ( context.getLog().isTraceEnabled() ) {
                context.getLog().trace("No updater for " + context.getCurrentElement());
            }
        } else {
            updater.update(context, value);
        }

        String poppedElement = context.popElement();
    }




    /** 
    * Factory method to create new bean instances 
    *
    * @param namespace the namespace for the element
    * @param name the local name
    * @param attributes the <code>Attributes</code> used to match <code>ID/IDREF</code>
    * @return the created bean
    */
    protected Object createBean(
        String namespace,
        String name,
        Attributes attributes,
        ElementDescriptor descriptor,
        ReadContext context) {
        // TODO: recycle element mappings 
        // Maybe should move the current mapping into the context
        ElementMapping mapping = new ElementMapping();
        Class beanClass = descriptor.getSingularPropertyType();
        if (beanClass != null && beanClass.isArray()) {
            beanClass = beanClass.getComponentType();
        }

        // TODO: beanClass can be deduced from descriptor
        // so probably 
        mapping.setType(beanClass);
        mapping.setNamespace(namespace);
        mapping.setName(name);
        mapping.setAttributes(attributes);
        mapping.setDescriptor(descriptor);

        Object newInstance =
            context.getBeanCreationChain().create(mapping, context);

        return newInstance;
    }

    /** Allows the navigation from a reference to a property object to the 
    * descriptor defining what the property is. i.e. doing the join from a reference 
    * to a type to lookup its descriptor.
    * This could be done automatically by the NodeDescriptors. 
    * Refer to TODO.txt for more info.
    *
    * @param propertyDescriptor find descriptor for property object 
    * referenced by this descriptor
    * @return descriptor for the singular property class type referenced.
    */
    ElementDescriptor getElementDescriptor(
        ElementDescriptor propertyDescriptor,
        ReadContext context) {
        Log log = context.getLog();
        Class beanClass = propertyDescriptor.getSingularPropertyType();
        if (beanClass != null && !Map.class.isAssignableFrom(beanClass)) {
            if (beanClass.isArray()) {
                beanClass = beanClass.getComponentType();
            }
            if (log.isTraceEnabled()) {
                log.trace("Filling descriptor for: " + beanClass);
            }
            try {
                XMLBeanInfo xmlInfo =
                    context.getXMLIntrospector().introspect(beanClass);
                return xmlInfo.getElementDescriptor();

            } catch (Exception e) {
                log.warn("Could not introspect class: " + beanClass, e);
            }
        }
        // could not find a better descriptor so use the one we've got
        return propertyDescriptor;
    }

}