001 /*
002 * Copyright 2011 The Kuali Foundation.
003 *
004 * Licensed under the Educational Community License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.opensource.org/licenses/ecl2.php
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016 package org.kuali.kfs.fp.dataaccess;
017
018 import java.util.Map;
019
020 import org.apache.ojb.broker.PersistenceBroker;
021 import org.apache.ojb.broker.PersistenceBrokerException;
022 import org.apache.ojb.broker.PersistenceBrokerFactory;
023 import org.apache.ojb.broker.accesslayer.RowReaderDefaultImpl;
024 import org.apache.ojb.broker.metadata.ClassDescriptor;
025
026 /**
027 * (Inspired by example posted at http://nagoya.apache.org/eyebrowse/ReadMsg?listName=ojb-user@db.apache.org&msgId=749837) This
028 * class enables mapping multiple (presumably similar) classes to a single database table. Subclasses must implement the
029 * getDiscriminatorColumns method, returning a String array of columns to consider when determining which class to return, as well
030 * as implement the corresponding chooseClass method that acts on received values for those columns. Sample OBJ config:
031 * <class-descriptor class="org.kuali.bo.ClassA" table="some_common_table" row-reader="org.kuali.dao.ojb.ClassADiscriminator"> ...
032 * </class-descriptor> <class-descriptor class="org.kuali.bo.ClassB" table="some_common_table"
033 * row-reader="org.kuali.dao.ojb.ClassBDiscriminator"> ... </class-descriptor> (where ClassADiscriminator and ClassBDiscriminator
034 * extend PolymorphicMultiColumnDiscriminator)
035 */
036 public abstract class PolymorphicMultiColumnDiscriminator extends RowReaderDefaultImpl {
037
038 /** Column(s) that distinguish the parent class */
039 private String[] column = null;
040
041 public PolymorphicMultiColumnDiscriminator(ClassDescriptor cld) {
042 super(cld);
043 column = getDiscriminatorColumns();
044 }
045
046 /**
047 * This method should return the column(s) necessary to determine which class to cast to.
048 *
049 * @return one or more column names
050 */
051 public abstract String[] getDiscriminatorColumns();
052
053 /**
054 * Based on the received key values, this method determines the appropriate class.
055 *
056 * @param values
057 * @return an appropriately chosen class
058 */
059 public abstract Class chooseClass(String[] values);
060
061 protected ClassDescriptor selectClassDescriptor(Map row) throws PersistenceBrokerException {
062 String[] key = new String[column.length];
063
064 for (int i = 0; i < column.length; i++) {
065 key[i] = (String) row.get(column[i]);
066 }
067
068 Class clazz = null;
069
070 if (key != null) {
071 clazz = chooseClass(key);
072 }
073 if (clazz == null) {
074 return getClassDescriptor();
075 }
076
077 PersistenceBroker broker = null;
078 try {
079 broker = PersistenceBrokerFactory.defaultPersistenceBroker();
080 ClassDescriptor result = broker.getClassDescriptor(clazz);
081 broker.close();
082 if (result == null) {
083 return getClassDescriptor();
084 }
085 else {
086 return result;
087 }
088 }
089 catch (PersistenceBrokerException e) {
090 broker.close();
091 throw e;
092 }
093 }
094
095 }