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    1   /*
    2    * Licensed to the Apache Software Foundation (ASF) under one or more
    3    * contributor license agreements.  See the NOTICE file distributed with
    4    * this work for additional information regarding copyright ownership.
    5    * The ASF licenses this file to You under the Apache License, Version 2.0
    6    * (the "License"); you may not use this file except in compliance with
    7    * the License.  You may obtain a copy of the License at
    8    * 
    9    *     http://www.apache.org/licenses/LICENSE-2.0
   10    * 
   11    * Unless required by applicable law or agreed to in writing, software 
   12    * distributed under the License is distributed on an "AS IS" BASIS, 
   13    * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
   14    * See the License for the specific language governing permissions and 
   15    * limitations under the License.
   16    */
   17   
   18   package org.apache.jdo.impl.model.jdo;
   19   
   20   import org.apache.jdo.model.jdo.JDOClass;
   21   import org.apache.jdo.model.jdo.JDOMember;
   22   
   23   /**
   24    * This is the super interface for named JDO metadata elements, 
   25    * such as JDOClass and JDOField.
   26    *
   27    * @author Michael Bouschen
   28    */
   29   public class JDOMemberImpl
   30       extends JDOElementImpl
   31       implements JDOMember
   32   {
   33       /** Property name.*/
   34       private String name;
   35   
   36       /** Relationship JDOClass<->JDOMember. */
   37       private JDOClass declaringClass;
   38   
   39       /** Constructor. */
   40       protected JDOMemberImpl(String name, JDOClass declaringClass)
   41       {
   42           this.name = name;
   43           this.declaringClass = declaringClass;
   44       }
   45   
   46       /**
   47        * Returns the name of this JDOMember.
   48        * @return the name
   49        */
   50       public String getName()
   51       {
   52           return name;
   53       }
   54   
   55       /** 
   56        * Get the declaring class of this JDOMember.
   57        * @return the class that owns this JDOMember, or <code>null</code>
   58        * if the element is not attached to any class
   59        */
   60       public JDOClass getDeclaringClass()
   61       {
   62           return declaringClass;
   63       }
   64   
   65       //================= redefinition of java.lang.Object methods ================
   66       
   67       /** 
   68        * Overrides Object's <code>toString</code> method to return the name
   69        * of this persistence element.
   70        * @return a string representation of the object
   71        */
   72       public String toString () 
   73       { 
   74           return getName(); 
   75       }
   76       
   77       /** 
   78        * Overrides Object's <code>equals</code> method by comparing the name 
   79        * of this member with the name of the argument obj. The method returns 
   80        * <code>false</code> if obj does not have the same dynamic type as this 
   81        * member.
   82        * @return <code>true</code> if this object is the same as the obj argument;
   83        * <code>false</code> otherwise.
   84        * @param obj the reference object with which to compare.
   85        */
   86       public boolean equals(Object obj)
   87       {
   88           if (obj == null)
   89               return false;
   90           if (obj == this)
   91               return true;
   92           
   93           // check for the right class and then do the name check by 
   94           // calling compareTo.
   95           return (getClass() == obj.getClass()) && (compareTo(obj) == 0);
   96       }
   97       
   98       /** Overrides Object's <code>hashCode</code> method to return the hashCode 
   99        * of this name.
  100        * @return a hash code value for this object.
  101        */
  102       public int hashCode()
  103       {
  104           return (getName()==null) ? 0 : getName().hashCode();
  105       }
  106       
  107       //================= implementation of Comparable ================
  108       
  109       /** 
  110        * Compares this object with the specified object for order. Returns a 
  111        * negative integer, zero, or a positive integer as this object is less than, 
  112        * equal to, or greater than the specified object. The specified object must 
  113        * be a an instance of JDOMember, if not a ClassCastException is thrown.
  114        * The order of JDOMember instances is defined by the order of their names.
  115        * JDOMember instances without name are considered to be less than any named 
  116        * member.
  117        * @param o the Object to be compared.
  118        * @return a negative integer, zero, or a positive integer as this object is
  119        * less than, equal to, or greater than the specified object.
  120        * @exception ClassCastException - if the specified object is null or is not 
  121        * an instance of JDOMember
  122        */
  123       public int compareTo(Object o)
  124       {
  125           // null is not allowed
  126           if (o == null)
  127               throw new ClassCastException();
  128           if (o == this)
  129               return 0;
  130           
  131           String thisName = getName();
  132           // the following throws a ClassCastException if o is not a JDOMember
  133           String otherName = ((JDOMember)o).getName();
  134           // if this does not have a name it should compare less than any named
  135           if (thisName == null) {
  136               return (otherName == null) ? 0 : -1;
  137           }
  138           
  139           // if this is named and o does not have a name it should compare greater
  140           if (otherName == null) {
  141               return 1;
  142           }
  143           
  144           // now we know that this and o are named JDOMembers => compare the names
  145           int ret = thisName.compareTo(otherName);
  146           // If both names are equal, both objects might have different types.
  147           // If so order both objects by their type names 
  148           // (necessary to be consistent with equals)
  149           if ((ret == 0) && (getClass() != o.getClass()))
  150               ret = getClass().getName().compareTo(o.getClass().getName());
  151           return ret;
  152       }
  153   }

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