Returns the value of the given property for the given bean. - Java Reflection

Java examples for Reflection:Java Bean

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Description

Returns the value of the given property for the given bean.

Demo Code

/*******************************************************************************
 * Copyright (C) 2011 Angelo Zerr <angelo.zerr@gmail.com>, Pascal Leclercq <pascal.leclercq@gmail.com>
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:/*from w w  w . j av a2s  . c o m*/
 *     Angelo ZERR - initial API and implementation
 *     Pascal Leclercq - initial API and implementation
 *******************************************************************************/
//package com.java2s;
import java.beans.BeanInfo;
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.List;

public class Main {

    /**
     * Returns the value of the given property for the given bean.
     * 
     * @param source
     *            the source bean
     * @param property
     *            the property name to retrieve
     * @return the value of the given property for the given bean.
     */
    public static Object getValue(Object source, String property) {
        if (property == null) {
            return source;
        }
        if (property.indexOf('.') == -1) {
            if (source == null) {
                return null;
            }
            PropertyDescriptor propertyDescriptor = getPropertyDescriptor(
                    source.getClass(), property);
            return getValue(source, propertyDescriptor);
        }

        String[] properies = property.split("[.]");
        for (int i = 0; i < properies.length; i++) {
            source = getValue(source, properies[i]);
        }
        return source;
    }

    /**
     * Returns the value of the given property for the given bean.
     * 
     * @param source
     *            the source bean
     * @param propertyDescriptor
     *            the property to retrieve
     * @return the contents of the given property for the given bean.
     */
    private static Object getValue(Object source,
            PropertyDescriptor propertyDescriptor) {
        try {
            Method readMethod = propertyDescriptor.getReadMethod();
            if (readMethod == null) {
                throw new IllegalArgumentException(
                        propertyDescriptor.getName()
                                + " property does not have a read method."); //$NON-NLS-1$
            }
            if (!readMethod.isAccessible()) {
                readMethod.setAccessible(true);
            }
            return readMethod.invoke(source, null);
        } catch (InvocationTargetException e) {
            /*
             * InvocationTargetException wraps any exception thrown by the
             * invoked method.
             */
            throw new RuntimeException(e.getCause());
        } catch (Exception e) {
            return null;
        }
    }

    /**
     * Returns the property descriptor of the given bean class and the given
     * property.
     * 
     * @param beanClass
     * @param propertyName
     * @return the PropertyDescriptor for the named property on the given bean
     *         class
     */
    private static PropertyDescriptor getPropertyDescriptor(
            Class beanClass, String propertyName) {
        if (!beanClass.isInterface()) {
            BeanInfo beanInfo;
            try {
                beanInfo = Introspector.getBeanInfo(beanClass);
            } catch (IntrospectionException e) {
                // cannot introspect, give up
                return null;
            }
            PropertyDescriptor[] propertyDescriptors = beanInfo
                    .getPropertyDescriptors();
            for (int i = 0; i < propertyDescriptors.length; i++) {
                PropertyDescriptor descriptor = propertyDescriptors[i];
                if (descriptor.getName().equals(propertyName)) {
                    return descriptor;
                }
            }
        } else {
            try {
                PropertyDescriptor propertyDescriptors[];
                List pds = new ArrayList();
                getInterfacePropertyDescriptors(pds, beanClass);
                if (pds.size() > 0) {
                    propertyDescriptors = (PropertyDescriptor[]) pds
                            .toArray(new PropertyDescriptor[pds.size()]);
                    PropertyDescriptor descriptor;
                    for (int i = 0; i < propertyDescriptors.length; i++) {
                        descriptor = propertyDescriptors[i];
                        if (descriptor.getName().equals(propertyName))
                            return descriptor;
                    }
                }
            } catch (IntrospectionException e) {
                // cannot introspect, give up
                return null;
            }
        }
        throw new IllegalArgumentException(
                "Could not find property with name " + propertyName + " in class " + beanClass); //$NON-NLS-1$ //$NON-NLS-2$
    }

    /**
     * Goes recursively into the interface and gets all defined
     * propertyDescriptors
     * 
     * @param propertyDescriptors
     *            The result list of all PropertyDescriptors the given interface
     *            defines (hierarchical)
     * @param iface
     *            The interface to fetch the PropertyDescriptors
     * @throws IntrospectionException
     */
    private static void getInterfacePropertyDescriptors(
            List propertyDescriptors, Class iface)
            throws IntrospectionException {
        BeanInfo beanInfo = Introspector.getBeanInfo(iface);
        PropertyDescriptor[] pds = beanInfo.getPropertyDescriptors();
        for (int i = 0; i < pds.length; i++) {
            PropertyDescriptor pd = pds[i];
            propertyDescriptors.add(pd);
        }
        Class[] subIntfs = iface.getInterfaces();
        for (int j = 0; j < subIntfs.length; j++) {
            getInterfacePropertyDescriptors(propertyDescriptors,
                    subIntfs[j]);
        }
    }
}

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