Struts example source code file (BeanAdapter.java)

This example Struts source code file (BeanAdapter.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

bean, beanadapter, beanadapter, class, dom, exception, invocationtargetexception, javabean, list, nodelist, nullparams, object, object, propertydescriptor, propertydescriptor, reflection, string, string, util

The Struts BeanAdapter.java source code

/*
 * $Id: BeanAdapter.java 651946 2008-04-27 13:41:38Z apetrelli $
 *
 * 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.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.struts2.StrutsException;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

import com.opensymphony.xwork2.util.logging.Logger;
import com.opensymphony.xwork2.util.logging.LoggerFactory;


/**
 * This class is the most general type of adapter, utilizing reflective introspection to present a DOM view of all of
 * the public properties of its value.  For example, a property returning a JavaBean such as:
 *
 * <pre>
 * public Person getMyPerson() { ... }
 * ...
 * class Person {
 *      public String getFirstName();
 *      public String getLastName();
 * }
 * </pre>
 *
 * would be rendered as: <myPerson> ... ... 
 */
public class BeanAdapter extends AbstractAdapterElement {
    //~ Static fields/initializers /////////////////////////////////////////////

    private static final Object[] NULLPARAMS = new Object[0];

    /**
     * Cache can savely be static because the cached information is the same for all instances of this class.
     */
    private static Map<Class, PropertyDescriptor[]> propertyDescriptorCache;

    //~ Instance fields ////////////////////////////////////////////////////////

    private Logger log = LoggerFactory.getLogger(this.getClass());

    //~ Constructors ///////////////////////////////////////////////////////////

    public BeanAdapter() {
    }

    public BeanAdapter(
            AdapterFactory adapterFactory, AdapterNode parent, String propertyName, Object value) {
        setContext(adapterFactory, parent, propertyName, value);
    }

    //~ Methods ////////////////////////////////////////////////////////////////

    public String getTagName() {
        return getPropertyName();
    }

    public NodeList getChildNodes() {
        NodeList nl = super.getChildNodes();
        // Log child nodes for debug:
        if (log.isDebugEnabled() && nl != null) {
            log.debug("BeanAdapter getChildNodes for: " + getTagName());
            log.debug(nl.toString());
        }
        return nl;
    }

    protected List<Node> buildChildAdapters() {
        log.debug("BeanAdapter building children.  PropName = " + getPropertyName());
        List<Node> newAdapters = new ArrayList();
        Class type = getPropertyValue().getClass();
        PropertyDescriptor[] props = getPropertyDescriptors(getPropertyValue());

        if (props.length > 0) {
            for (PropertyDescriptor prop : props) {
                Method m = prop.getReadMethod();

                if (m == null) {
                    //FIXME: write only property or indexed access
                    continue;
                }
                log.debug("Bean reading property method: " + m.getName());

                String propertyName = prop.getName();
                Object propertyValue;

                /*
                    Unwrap any invocation target exceptions and log them.
                    We really need a way to control which properties are accessed.
                    Perhaps with annotations in Java5?
                */
                try {
                    propertyValue = m.invoke(getPropertyValue(), NULLPARAMS);
                } catch (Exception e) {
                    if (e instanceof InvocationTargetException)
                        e = (Exception) ((InvocationTargetException) e).getTargetException();
                    log.error("Cannot access bean property: "+propertyName, e);
                    continue;
                }

                Node childAdapter;

                if (propertyValue == null) {
                    childAdapter = getAdapterFactory().adaptNullValue(this, propertyName);
                } else {
                    childAdapter = getAdapterFactory().adaptNode(this, propertyName, propertyValue);
                }

                if (childAdapter != null)
                    newAdapters.add(childAdapter);

                if (log.isDebugEnabled()) {
                    log.debug(this + " adding adapter: " + childAdapter);
                }
            }
        } else {
            // No properties found
            log.info(
                    "Class " + type.getName() + " has no readable properties, " + " trying to adapt " + getPropertyName() + " with StringAdapter...");
        }

        return newAdapters;
    }

    /**
     * Caching facade method to Introspector.getBeanInfo(Class, Class).getPropertyDescriptors();
     */
    private synchronized PropertyDescriptor[] getPropertyDescriptors(Object bean) {
        try {
            if (propertyDescriptorCache == null) {
                propertyDescriptorCache = new HashMap<Class, PropertyDescriptor[]>();
            }

            PropertyDescriptor[] props = propertyDescriptorCache.get(bean.getClass());

            if (props == null) {
                log.debug("Caching property descriptor for " + bean.getClass().getName());
                props = Introspector.getBeanInfo(bean.getClass(), Object.class).getPropertyDescriptors();
                propertyDescriptorCache.put(bean.getClass(), props);
            }

            return props;
        } catch (IntrospectionException e) {
            e.printStackTrace();
            throw new StrutsException("Error getting property descriptors for " + bean + " : " + e.getMessage());
        }
    }
}