1 /*
2 * Copyright 2005 The Kuali Foundation
3 *
4 * Licensed under the Educational Community License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.opensource.org/licenses/ecl2.php
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16 package org.kuali.ole.fp.dataaccess;
17
18 import java.util.Map;
19
20 import org.apache.ojb.broker.PersistenceBroker;
21 import org.apache.ojb.broker.PersistenceBrokerException;
22 import org.apache.ojb.broker.PersistenceBrokerFactory;
23 import org.apache.ojb.broker.accesslayer.RowReaderDefaultImpl;
24 import org.apache.ojb.broker.metadata.ClassDescriptor;
25
26 /**
27 * (Inspired by example posted at http://nagoya.apache.org/eyebrowse/ReadMsg?listName=ojb-user@db.apache.org&msgId=749837) This
28 * class enables mapping multiple (presumably similar) classes to a single database table. Subclasses must implement the
29 * getDiscriminatorColumns method, returning a String array of columns to consider when determining which class to return, as well
30 * as implement the corresponding chooseClass method that acts on received values for those columns. Sample OBJ config:
31 * <class-descriptor class="org.kuali.bo.ClassA" table="some_common_table" row-reader="org.kuali.dao.ojb.ClassADiscriminator"> ...
32 * </class-descriptor> <class-descriptor class="org.kuali.bo.ClassB" table="some_common_table"
33 * row-reader="org.kuali.dao.ojb.ClassBDiscriminator"> ... </class-descriptor> (where ClassADiscriminator and ClassBDiscriminator
34 * extend PolymorphicMultiColumnDiscriminator)
35 */
36 public abstract class PolymorphicMultiColumnDiscriminator extends RowReaderDefaultImpl {
37
38 /** Column(s) that distinguish the parent class */
39 private String[] column = null;
40
41 public PolymorphicMultiColumnDiscriminator(ClassDescriptor cld) {
42 super(cld);
43 column = getDiscriminatorColumns();
44 }
45
46 /**
47 * This method should return the column(s) necessary to determine which class to cast to.
48 *
49 * @return one or more column names
50 */
51 public abstract String[] getDiscriminatorColumns();
52
53 /**
54 * Based on the received key values, this method determines the appropriate class.
55 *
56 * @param values
57 * @return an appropriately chosen class
58 */
59 public abstract Class chooseClass(String[] values);
60
61 protected ClassDescriptor selectClassDescriptor(Map row) throws PersistenceBrokerException {
62 String[] key = new String[column.length];
63
64 for (int i = 0; i < column.length; i++) {
65 key[i] = (String) row.get(column[i]);
66 }
67
68 Class clazz = null;
69
70 if (key != null) {
71 clazz = chooseClass(key);
72 }
73 if (clazz == null) {
74 return getClassDescriptor();
75 }
76
77 PersistenceBroker broker = null;
78 try {
79 broker = PersistenceBrokerFactory.defaultPersistenceBroker();
80 ClassDescriptor result = broker.getClassDescriptor(clazz);
81 broker.close();
82 if (result == null) {
83 return getClassDescriptor();
84 }
85 else {
86 return result;
87 }
88 }
89 catch (PersistenceBrokerException e) {
90 broker.close();
91 throw e;
92 }
93 }
94
95 }