从传递的pojo中返回指定属性的值。

/**

 * Helios, OpenSource Monitoring

 * Brought to you by the Helios Development Group

 *

 * Copyright 2007, Helios Development Group and individual contributors

 * as indicated by the @author tags. See the copyright.txt file in the

 * distribution for a full listing of individual contributors.

 *

 * This is free software; you can redistribute it and/or modify it

 * under the terms of the GNU Lesser General Public License as

 * published by the Free Software Foundation; either version 2.1 of

 * the License, or (at your option) any later version.

 *

 * This software 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

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with this software; if not, write to the Free

 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA

 * 02110-1301 USA, or see the FSF site: http://www.fsf.org. 

 *

 *//** 来自 nowjava.com - 时代Java**/

//package com.nowjava;

import java.beans.*;


import java.util.ArrayList;


import java.util.List;


public class Main {

    public static void main(String[] argv) throws Exception {

        String name = "nowjava.com";

        Object target = "nowjava.com";

        System.out.println(getAttribute(name, target));

    }


    /**

     * Returns the value of the named attribute from the passed pojo.

     * @param name The name of the attribute.

     * @param target The target pojo to retrieve the value from.

     * @return the value of the named attribute.

     */

    public static Object getAttribute(String name, Object target) {

        try {
        /*
        时 代      J a v a   公   众 号 - nowjava.com 提 供
        */

            Class<?> targetType = getAttributeType(target.getClass(), name);

            PropertyEditor propertyEditor = PropertyEditorManager

                    .findEditor(targetType);

            if (propertyEditor == null)

                throw new RuntimeException(

                        "No PropertyEditor Found for type ["

                                + targetType.getName()

                                + "] in object of type + ["

                                + target.getClass().getName() + "]");


            Expression expression = new Expression(target,

                    getPropertyDescriptor(target.getClass(), name)

                            .getReadMethod().getName(), new Object[] {});

            expression.execute();

            return expression.getValue();


        } catch (Exception e) {

            throw new RuntimeException("Failed to get attribute [" + name

                    + "] on instance of  [" + target.getClass().getName()

                    + "]");

        }


    }


    /**

     * Determines the type of the named parameter for the passed type.

     * @param targetType The target type to invoke against.

     * @param name The attribute name.

     * @return The class of the parameter type

     */

    public static Class<?> getAttributeType(Class<?> targetType, String name) {

        PropertyDescriptor pd = getPropertyDescriptor(targetType, name);

        return pd.getPropertyType();

    }


    /**

     * Locates the PropertyDescriptor for the passed name in the passed class.

     * @param targetType

     * @param name

     * @return A PropertyDescriptor

     */

    public static PropertyDescriptor getPropertyDescriptor(

            Class<?> targetType, String name) {

        String dName = Introspector.decapitalize(name);

        try {

            BeanInfo bi = Introspector.getBeanInfo(targetType);

            for (PropertyDescriptor pd : bi.getPropertyDescriptors()) {

                if (pd.getName().equals(dName)) {

                    return pd;

                }

            }

            throw new Exception("No PropertyDescriptor found for " + name);

        } catch (Exception e) {

            throw new RuntimeException(

                    "Failed to Acquire PropertyDescriptor for ["

                            + targetType.getName() + "/" + name + "]", e);

        }


    }


    public static BeanInfo getBeanInfo(Object pojo) {

        try {

            return Introspector.getBeanInfo(pojo.getClass());

        } catch (Exception e) {

            throw new RuntimeException("Failed to create bean info", e);

        }

    }


    /**

     * Returns a list of a pojo's <code>PropertyDescriptor</code>s minus the same for <code>java.lang.Object</code>.

     * @param pojo

     * @return A list of <code>PropertyDescriptor</code>s.

     */

    public static List<