Java example source code file (PropertyElementHandler.java)

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

Learn more about this Java project at its project page.

Java - Java tags/keywords

bean, class, could, getter, illegalaccessexception, indexedpropertydescriptor, integer, introspectionexception, javabean, method, non\-nls, nosuchmethodexception, object, override, reflection, setter, string

The PropertyElementHandler.java Java example source code

/*
 * Copyright (c) 2008, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package com.sun.beans.decoder;

import com.sun.beans.finder.MethodFinder;

import java.beans.IndexedPropertyDescriptor;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;

import java.lang.reflect.Array;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import sun.reflect.misc.MethodUtil;

/**
 * This class is intended to handle <property> element.
 * This element simplifies access to the properties.
 * If the {@code index} attribute is specified
 * this element uses additional {@code int} parameter.
 * If the {@code name} attribute is not specified
 * this element uses method "get" as getter
 * and method "set" as setter.
 * This element defines getter if it contains no argument.
 * It returns the value of the property in this case.
 * For example:<pre>
 * <property name="object" index="10"/></pre>
 * is shortcut to<pre>
 * <method name="getObject">
 *     <int>10</int>
 * </method></pre>
 * which is equivalent to {@code getObject(10)} in Java code.
 * This element defines setter if it contains one argument.
 * It does not return the value of the property in this case.
 * For example:<pre>
 * <property><int>0</int></property></pre>
 * is shortcut to<pre>
 * <method name="set">
 *     <int>0</int>
 * </method></pre>
 * which is equivalent to {@code set(0)} in Java code.
 * <p>The following attributes are supported:
 * <dl>
 * <dt>name
 * <dd>the property name
 * <dt>index
 * <dd>the property index
 * <dt>id
 * <dd>the identifier of the variable that is intended to store the result
 * </dl>
 *
 * @since 1.7
 *
 * @author Sergey A. Malenkov
 */
final class PropertyElementHandler extends AccessorElementHandler {
    static final String GETTER = "get"; // NON-NLS: the getter prefix
    static final String SETTER = "set"; // NON-NLS: the setter prefix

    private Integer index;

    /**
     * Parses attributes of the element.
     * The following attributes are supported:
     * <dl>
     * <dt>name
     * <dd>the property name
     * <dt>index
     * <dd>the property index
     * <dt>id
     * <dd>the identifier of the variable that is intended to store the result
     * </dl>
     *
     * @param name   the attribute name
     * @param value  the attribute value
     */
    @Override
    public void addAttribute(String name, String value) {
        if (name.equals("index")) { // NON-NLS: the attribute name
            this.index = Integer.valueOf(value);
        } else {
            super.addAttribute(name, value);
        }
    }

    /**
     * Tests whether the value of this element can be used
     * as an argument of the element that contained in this one.
     *
     * @return {@code true} if the value of this element should be used
     *         as an argument of the element that contained in this one,
     *         {@code false} otherwise
     */
    @Override
    protected boolean isArgument() {
        return false; // non-static accessor cannot be used an argument
    }

    /**
     * Returns the value of the property with specified {@code name}.
     *
     * @param name  the name of the property
     * @return the value of the specified property
     */
    @Override
    protected Object getValue(String name) {
        try {
            return getPropertyValue(getContextBean(), name, this.index);
        }
        catch (Exception exception) {
            getOwner().handleException(exception);
        }
        return null;
    }

    /**
     * Sets the new value for the property with specified {@code name}.
     *
     * @param name   the name of the property
     * @param value  the new value for the specified property
     */
    @Override
    protected void setValue(String name, Object value) {
        try {
            setPropertyValue(getContextBean(), name, this.index, value);
        }
        catch (Exception exception) {
            getOwner().handleException(exception);
        }
    }

    /**
     * Performs the search of the getter for the property
     * with specified {@code name} in specified class
     * and returns value of the property.
     *
     * @param bean   the context bean that contains property
     * @param name   the name of the property
     * @param index  the index of the indexed property
     * @return the value of the property
     * @throws IllegalAccessException    if the property is not accesible
     * @throws IntrospectionException    if the bean introspection is failed
     * @throws InvocationTargetException if the getter cannot be invoked
     * @throws NoSuchMethodException     if the getter is not found
     */
    private static Object getPropertyValue(Object bean, String name, Integer index) throws IllegalAccessException, IntrospectionException, InvocationTargetException, NoSuchMethodException {
        Class<?> type = bean.getClass();
        if (index == null) {
            return MethodUtil.invoke(findGetter(type, name), bean, new Object[] {});
        } else if (type.isArray() && (name == null)) {
            return Array.get(bean, index);
        } else {
            return MethodUtil.invoke(findGetter(type, name, int.class), bean, new Object[] {index});
        }
    }

    /**
     * Performs the search of the setter for the property
     * with specified {@code name} in specified class
     * and updates value of the property.
     *
     * @param bean   the context bean that contains property
     * @param name   the name of the property
     * @param index  the index of the indexed property
     * @param value  the new value for the property
     * @throws IllegalAccessException    if the property is not accesible
     * @throws IntrospectionException    if the bean introspection is failed
     * @throws InvocationTargetException if the setter cannot be invoked
     * @throws NoSuchMethodException     if the setter is not found
     */
    private static void setPropertyValue(Object bean, String name, Integer index, Object value) throws IllegalAccessException, IntrospectionException, InvocationTargetException, NoSuchMethodException {
        Class<?> type = bean.getClass();
        Class<?> param = (value != null)
                ? value.getClass()
                : null;

        if (index == null) {
            MethodUtil.invoke(findSetter(type, name, param), bean, new Object[] {value});
        } else if (type.isArray() && (name == null)) {
            Array.set(bean, index, value);
        } else {
            MethodUtil.invoke(findSetter(type, name, int.class, param), bean, new Object[] {index, value});
        }
    }

    /**
     * Performs the search of the getter for the property
     * with specified {@code name} in specified class.
     *
     * @param type  the class that contains method
     * @param name  the name of the property
     * @param args  the method arguments
     * @return method object that represents found getter
     * @throws IntrospectionException if the bean introspection is failed
     * @throws NoSuchMethodException  if method is not found
     */
    private static Method findGetter(Class<?> type, String name, Class...args) throws IntrospectionException, NoSuchMethodException {
        if (name == null) {
            return MethodFinder.findInstanceMethod(type, GETTER, args);
        }
        PropertyDescriptor pd = getProperty(type, name);
        if (args.length == 0) {
            Method method = pd.getReadMethod();
            if (method != null) {
                return method;
            }
        } else if (pd instanceof IndexedPropertyDescriptor) {
            IndexedPropertyDescriptor ipd = (IndexedPropertyDescriptor) pd;
            Method method = ipd.getIndexedReadMethod();
            if (method != null) {
                return method;
            }
        }
        throw new IntrospectionException("Could not find getter for the " + name + " property");
    }

    /**
     * Performs the search of the setter for the property
     * with specified {@code name} in specified class.
     *
     * @param type  the class that contains method
     * @param name  the name of the property
     * @param args  the method arguments
     * @return method object that represents found setter
     * @throws IntrospectionException if the bean introspection is failed
     * @throws NoSuchMethodException  if method is not found
     */
    private static Method findSetter(Class<?> type, String name, Class...args) throws IntrospectionException, NoSuchMethodException {
        if (name == null) {
            return MethodFinder.findInstanceMethod(type, SETTER, args);
        }
        PropertyDescriptor pd = getProperty(type, name);
        if (args.length == 1) {
            Method method = pd.getWriteMethod();
            if (method != null) {
                return method;
            }
        } else if (pd instanceof IndexedPropertyDescriptor) {
            IndexedPropertyDescriptor ipd = (IndexedPropertyDescriptor) pd;
            Method method = ipd.getIndexedWriteMethod();
            if (method != null) {
                return method;
            }
        }
        throw new IntrospectionException("Could not find setter for the " + name + " property");
    }

    /**
     * Performs the search of the descriptor for the property
     * with specified {@code name} in specified class.
     *
     * @param type  the class to introspect
     * @param name  the property name
     * @return descriptor for the named property
     * @throws IntrospectionException if property descriptor is not found
     */
    private static PropertyDescriptor getProperty(Class<?> type, String name) throws IntrospectionException {
        for (PropertyDescriptor pd : Introspector.getBeanInfo(type).getPropertyDescriptors()) {
            if (name.equals(pd.getName())) {
                return pd;
            }
        }
        throw new IntrospectionException("Could not find the " + name + " property descriptor");
    }
}