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Struts example source code file (AdapterFactory.java)

This example Struts source code file (AdapterFactory.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Struts tags/keywords

adapternode, class, class, document, document, dom, illegalaccessexception, instantiationexception, namednodemap, node, node, object, string, string, strutsexception, util

The Struts AdapterFactory.java source code

/*
 * $Id: AdapterFactory.java 803589 2009-08-12 16:37:46Z musachy $
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.struts2.views.xslt;

import java.util.Collection;
import java.util.HashMap;
import java.util.Map;

import org.apache.struts2.StrutsException;
import org.w3c.dom.Attr;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.Text;

/**
 * AdapterFactory produces Node adapters for Java object types.
 * Adapter classes are generally instantiated dynamically via a no-args constructor
 * and populated with their context information via the AdapterNode interface.
 *
 * This factory supports proxying of generic DOM Node trees, allowing arbitrary
 * Node types to be mixed together.  You may simply return a Document or Node
 * type as an object property and it will appear as a sub-tree in the XML as
 * you'd expect. See #proxyNode().
 *
 * Customization of the result XML can be accomplished by providing
 * alternate adapters for Java types.  Adapters are associated with Java
 * types through the registerAdapterType() method.
 *
 * For example, since there is no default Date adapter, Date objects will be
 * rendered with the generic Bean introspecting adapter, producing output
 * like:
 * <pre>
     <date>
        <date>19
        <day>1
        <hours>0
        <minutes>7
        <month>8
        <seconds>4
        <time>1127106424531
        <timezoneOffset>300
        <year>105
    </date>
 * </pre>
 *
 * By extending the StringAdapter and overriding its normal behavior we can
 * create a custom Date formatter:
 *
 * <pre>
      public static class CustomDateAdapter extends StringAdapter {
        protected String getStringValue() {
            Date date = (Date)getPropertyValue();
            return DateFormat.getTimeInstance( DateFormat.FULL ).format( date );
        }
    }
 * </pre>
 *
 * Producing output like:
 *
<pre>
     <date>12:02:54 AM CDT
 </pre>
 *
 * The StringAdapter (which is normally invoked only to adapt String values)
 * is a useful base for these kinds of customizations and can produce
 * structured XML output as well as plain text by setting its parseStringAsXML()
 * property to true.
 *
 * See provided examples.
 */
public class AdapterFactory {

    private Map<Class, Class> adapterTypes = new HashMap();

    /**
     * Register an adapter type for a Java class type.
     *
     * @param type        the Java class type which is to be handled by the adapter.
     * @param adapterType The adapter class, which implements AdapterNode.
     */
    public void registerAdapterType(Class type, Class adapterType) {
        adapterTypes.put(type, adapterType);
    }

    /**
     * Create a top level Document adapter for the specified Java object.
     * The document will have a root element with the specified property name
     * and contain the specified Java object content.
     *
     * @param propertyName The name of the root document element
     * @return
     * @throws IllegalAccessException
     * @throws InstantiationException
     */
    public Document adaptDocument(String propertyName, Object propertyValue)
            throws IllegalAccessException, InstantiationException {
        //if ( propertyValue instanceof Document )
        //  return (Document)propertyValue;

        return new SimpleAdapterDocument(this, null, propertyName, propertyValue);
    }


    /**
     * Create an Node adapter for a child element.
     * Note that the parent of the created node must be an AdapterNode, however
     * the child node itself may be any type of Node.
     *
     * @see #adaptDocument( String, Object )
     */
    public Node adaptNode(AdapterNode parent, String propertyName, Object value) {
        Class adapterClass = getAdapterForValue(value);
        if (adapterClass != null)
            return constructAdapterInstance(adapterClass, parent, propertyName, value);

        // If the property is a Document, "unwrap" it to the root element
        if (value instanceof Document)
            value = ((Document) value).getDocumentElement();

        // If the property is already a Node, proxy it
        if (value instanceof Node)
            return proxyNode(parent, (Node) value);

        // Check other supported types or default to generic JavaBean introspecting adapter
        Class valueType = value.getClass();

        if (valueType.isArray())
            adapterClass = ArrayAdapter.class;
        else if (value instanceof String || value instanceof Number || value instanceof Boolean || valueType.isPrimitive())
            adapterClass = StringAdapter.class;
        else if (value instanceof Collection)
            adapterClass = CollectionAdapter.class;
        else if (value instanceof Map)
            adapterClass = MapAdapter.class;
        else
            adapterClass = BeanAdapter.class;

        return constructAdapterInstance(adapterClass, parent, propertyName, value);
    }

    /**
     * Construct a proxy adapter for a value that is an existing DOM Node.
     * This allows arbitrary DOM Node trees to be mixed in with our results.
     * The proxied nodes are read-only and currently support only
     * limited types of Nodes including Element, Text, and Attributes.  (Other
     * Node types may be ignored by the proxy and not appear in the result tree).
     * <p/>
     * // TODO:
     * NameSpaces are not yet supported.
     * <p/>
     * This method is primarily for use by the adapter node classes.
     */
    public Node proxyNode(AdapterNode parent, Node node) {
        // If the property is a Document, "unwrap" it to the root element
        if (node instanceof Document)
            node = ((Document) node).getDocumentElement();

        if (node == null)
            return null;
        if (node.getNodeType() == Node.ELEMENT_NODE)
            return new ProxyElementAdapter(this, parent, (Element) node);
        if (node.getNodeType() == Node.TEXT_NODE)
            return new ProxyTextNodeAdapter(this, parent, (Text) node);
        if (node.getNodeType() == Node.ATTRIBUTE_NODE)
            return new ProxyAttrAdapter(this, parent, (Attr) node);

        return null; // Unsupported Node type - ignore for now
    }

    public NamedNodeMap proxyNamedNodeMap(AdapterNode parent, NamedNodeMap nnm) {
        return new ProxyNamedNodeMap(this, parent, nnm);
    }

    /**
     * Create an instance of an adapter dynamically and set its context via
     * the AdapterNode interface.
     */
    private Node constructAdapterInstance(Class adapterClass, AdapterNode parent, String propertyName, Object propertyValue) {
        // Check to see if the class has a no-args constructor
        try {
            adapterClass.getConstructor(new Class []{});
        } catch (NoSuchMethodException e1) {
            throw new StrutsException("Adapter class: " + adapterClass
                    + " does not have a no-args consructor.");
        }

        try {
            AdapterNode adapterNode = (AdapterNode) adapterClass.newInstance();
            adapterNode.setAdapterFactory(this);
            adapterNode.setParent(parent);
            adapterNode.setPropertyName(propertyName);
            adapterNode.setPropertyValue(propertyValue);

            return adapterNode;

        } catch (IllegalAccessException e) {
            e.printStackTrace();
            throw new StrutsException("Cannot adapt " + propertyValue + " (" + propertyName + ") :" + e.getMessage());
        } catch (InstantiationException e) {
            e.printStackTrace();
            throw new StrutsException("Cannot adapt " + propertyValue + " (" + propertyName + ") :" + e.getMessage());
        }
    }

    /**
     * Create an appropriate adapter for a null value.
     *
     * @param parent
     * @param propertyName
     */
    public Node adaptNullValue(AdapterNode parent, String propertyName) {
        return new StringAdapter(this, parent, propertyName, "null");
    }

    //TODO: implement Configuration option to provide additional adapter classes
    public Class getAdapterForValue(Object value) {
        return adapterTypes.get(value.getClass());
    }
}

Other Struts examples (source code examples)

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