keypathhelper.java

把java对象映射成数据库表中的一条记录

/*
 * 
 * The contents of this file are subject to the Mozilla Public License
 * Version 1.1 (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.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
 * License for the specific language governing rights and limitations under
 * the License.
 *
 * The Original Code is jRelationalFramework. 
 *
 * The Initial Developer of the Original Code is is.com.
 * Portions created by is.com are Copyright (C) 2000 is.com.
 * All Rights Reserved.
 * 
 * Contributor(s): Tim Dawson ([e-mail])
 * Contributor(s): ____________________________________
 * 
 * Alternatively, the contents of this file may be used under the terms of
 * the GNU General Public License (the "GPL") or the GNU Lesser General
 * Public license (the "LGPL"), in which case the provisions of the GPL or
 * LGPL are applicable instead of those above.  If you wish to allow use of
 * your version of this file only under the terms of either the GPL or LGPL
 * and not to allow others to use your version of this file under the MPL,
 * indicate your decision by deleting the provisions above and replace them
 * with the notice and other provisions required by either the GPL or LGPL
 * License.  If you do not delete the provisions above, a recipient may use
 * your version of this file under either the MPL or GPL or LGPL License.
 *
 */
package com.is.util;


import java.lang.reflect.*;

import java.util.StringTokenizer;


/**
 *  This class executes recursive getter methods (no parameters) using
 *  reflection.
 *
 *  i.e.  If you have an Employee instance that has a Manager instance, you
 *  could get the name of the employees manager with this key path string:
 *  "getManager.getName"
 */
public class KeyPathHelper
  {

  /**
   * Recursively execute methods on the result of the previous method.
   *
   * @param obj a value of type 'Object' - i.e. an Employee instance
   * @param keyPath a value of type 'String' - i.e. "getManager.getName"
   * @return a value of type 'Object' - i.e. returns the managers name
   */
  public static Object getValueForKeyPath (Object obj, String keyPath)
          throws KeyPathException
    {

    // Use reflection to call the appropriate method name

    // Create the parameter list array (empty)
    Class[] emptyParms = new Class[]
        {};

    // Create the args object (empty)
    Object args[] = new Object[]
        {};

    // Create the result object
    Object result = null;
    String methodName = null;
    Method getMethod = null;
    Class valueClass = null;

    // Tokenize the keypath
    StringTokenizer st = new StringTokenizer(keyPath, ".");

    try
        {
        // Grab
        result = obj;
        while (st.hasMoreTokens())
            {
            methodName = st.nextToken();
            valueClass = result.getClass();
            getMethod = valueClass.getMethod(methodName, emptyParms);
            result = getMethod.invoke(result, args);
            }
        }
    catch (Exception e)
        {
        throw new KeyPathException(e);
        }
    return result;
    } // getValueForKeyPath(anObject,aString)
  

  public static class KeyPathException
      extends Exception
    {
    private Exception i_originalException = null;

    public KeyPathException(Exception e)
      {
      super();
      i_originalException = e;
      }

    public Exception getOriginalException()
      {
      return i_originalException;
      }

    public String toString()
      {
      return super.toString()
              + " [\n"
              + i_originalException.toString()
              + "]"; 
      }
    } // KeyPathException

  
  } // KeyPathHelper