1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
|
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Creating Indexed Collections</title>
<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
<link rel="start" href="index.html" title="Berkeley DB Collections Tutorial" />
<link rel="up" href="UsingSecondaries.html" title="Chapter 3. Using Secondary Indices" />
<link rel="prev" href="openingforeignkeys.html" title="More Secondary Key Indices" />
<link rel="next" href="retrievingbyindexkey.html" title="Retrieving Items by Index Key" />
</head>
<body>
<div xmlns="" class="navheader">
<div class="libver">
<p>Library Version 12.1.6.1</p>
</div>
<table width="100%" summary="Navigation header">
<tr>
<th colspan="3" align="center">
Creating Indexed Collections
</th>
</tr>
<tr>
<td width="20%" align="left"><a accesskey="p" href="openingforeignkeys.html">Prev</a> </td>
<th width="60%" align="center">Chapter 3.
Using Secondary Indices
</th>
<td width="20%" align="right"> <a accesskey="n" href="retrievingbyindexkey.html">Next</a></td>
</tr>
</table>
<hr />
</div>
<div class="sect1" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h2 class="title" style="clear: both"><a id="indexedcollections"></a>
Creating Indexed Collections
</h2>
</div>
</div>
</div>
<p>
In the prior Basic example, bindings and Java collections were
created for accessing databases via their primary keys. In this
example, bindings and collections are added for accessing the same
databases via their index keys. As in the prior example, serial
bindings and the Java
<a class="ulink" href="http://download.oracle.com/javase/1.5.0/docs/api/java/util/Map.html" target="_top">Map</a>
class are used.
</p>
<p>
When a map is created from a
<span>
<a class="ulink" href="../../java/com/sleepycat/db/SecondaryDatabase.html" target="_top">SecondaryDatabase</a>,
</span>
the keys of the map will be the index keys. However, the values of
the map will be the values of the primary database associated with
the index. This is how index keys can be used to access the values
in a primary database.
</p>
<p>
For example, the Supplier's City field is an index key that can
be used to access the Supplier database. When a map is created
using the <code class="methodname">supplierByCityDb()</code> method, the key to the map will be the
City field, a
<a class="ulink" href="http://download.oracle.com/javase/1.5.0/docs/api/java/lang/String.html" target="_top">String</a>
object. When
<a class="ulink" href="http://download.oracle.com/javase/1.5.0/docs/api/java/util/Map.html#get(java.lang.Object)" target="_top">Map.get</a>
is called passing the City as the key parameter, a
<code class="classname">SupplierData</code>
object will be returned.
</p>
<p>
The <code class="classname">SampleViews</code> class is extended to create an index key
binding for the Supplier's City field and three Java maps based on
the three indices created in the prior section.
</p>
<a id="index_sampleviews"></a>
<pre class="programlisting">import com.sleepycat.bind.EntryBinding;
import com.sleepycat.bind.serial.SerialBinding;
import com.sleepycat.collections.StoredEntrySet;
import com.sleepycat.collections.StoredSortedMap;
...
public class SampleViews
{
...
<strong class="userinput"><code> private StoredSortedMap supplierByCityMap;
private StoredSortedMap shipmentByPartMap;
private StoredSortedMap shipmentBySupplierMap;</code></strong>
...
public SampleViews(SampleDatabase db)
{
ClassCatalog catalog = db.getClassCatalog();
...
<strong class="userinput"><code> EntryBinding cityKeyBinding =
new SerialBinding(catalog, String.class);
...
supplierByCityMap =
new StoredSortedMap(db.getSupplierByCityDatabase(),
cityKeyBinding, supplierDataBinding, true);
shipmentByPartMap =
new StoredSortedMap(db.getShipmentByPartDatabase(),
partKeyBinding, supplierDataBinding, true);
shipmentBySupplierMap =
new StoredSortedMap(db.getShipmentBySupplierDatabase(),
supplierKeyBinding, supplierDataBinding, true); </code></strong>
...
}
} </pre>
<p>
In general, the indexed maps are created here in the same way as
the unindexed maps were created in the Basic example. The
differences are:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
The first parameter of the
<a class="ulink" href="../../java/com/sleepycat/collections/StoredMap.html" target="_top">StoredSortedMap</a>
constructor is a
<a class="ulink" href="../../java/com/sleepycat/db/SecondaryDatabase.html" target="_top">SecondaryDatabase</a>
rather than a
<span>
<a class="ulink" href="../../java/com/sleepycat/db/Database.html" target="_top">Database</a>.
</span>
</p>
</li>
<li>
<p>
The second parameter is the index key binding rather than the
primary key binding.
</p>
</li>
</ul>
</div>
<p>
For the <code class="literal">supplierByCityMap</code>, the <code class="literal">cityKeyBinding</code> must
first be created. This binding was not created in the Basic example
because the City field is not a primary key.
</p>
<p>
Like the bindings created earlier for keys and values, the
<code class="literal">cityKeyBinding</code> is a
<a class="ulink" href="../../java/com/sleepycat/bind/serial/SerialBinding.html" target="_top">SerialBinding</a>.
Unlike the bindings created earlier, it is an example of creating a
binding for a built-in Java class,
<a class="ulink" href="http://download.oracle.com/javase/1.5.0/docs/api/java/lang/String.html" target="_top">String</a>,
instead of an application-defined class. Any serializable class may
be used.
</p>
<p>
For the <code class="literal">shipmentByPartMap</code> and
<code class="literal">shipmentBySupplierMap</code>, the <code class="literal">partKeyBinding</code> and
<code class="literal">supplierKeyBinding</code> are used. These were created in the Basic
example and used as the primary key bindings for the <code class="literal">partMap</code>
and <code class="literal">supplierMap</code>.
</p>
<p>
The value bindings — <code class="literal">supplierDataBinding</code> and
<code class="literal">shipmentDataBinding</code> — were also created in the Basic
example.
</p>
<p>
This illustrates that bindings and formats may and should be
reused where appropriate for creating maps and other
collections.
</p>
<p>
The following getter methods return the stored maps for use by
other classes in the example program. Convenience methods for
returning entry sets are also included.
</p>
<a id="index_sampleviewsgetters"></a>
<pre class="programlisting">public class SampleViews
{
...
<strong class="userinput"><code> public final StoredSortedMap getShipmentByPartMap()
{
return shipmentByPartMap;
}
public final StoredSortedMap getShipmentBySupplierMap()
{
return shipmentBySupplierMap;
}
public final StoredSortedMap getSupplierByCityMap()
{
return supplierByCityMap;
}
public final StoredEntrySet getShipmentByPartEntrySet()
{
return (StoredEntrySet) shipmentByPartMap.entrySet();
}
public final StoredEntrySet getShipmentBySupplierEntrySet()
{
return (StoredEntrySet) shipmentBySupplierMap.entrySet();
}
public final StoredEntrySet getSupplierByCityEntrySet()
{
return (StoredEntrySet) supplierByCityMap.entrySet();
}</code></strong>
...
} </pre>
</div>
<div class="navfooter">
<hr />
<table width="100%" summary="Navigation footer">
<tr>
<td width="40%" align="left"><a accesskey="p" href="openingforeignkeys.html">Prev</a> </td>
<td width="20%" align="center">
<a accesskey="u" href="UsingSecondaries.html">Up</a>
</td>
<td width="40%" align="right"> <a accesskey="n" href="retrievingbyindexkey.html">Next</a></td>
</tr>
<tr>
<td width="40%" align="left" valign="top">
<span>More Secondary Key Indices</span>
</td>
<td width="20%" align="center">
<a accesskey="h" href="index.html">Home</a>
</td>
<td width="40%" align="right" valign="top">
Retrieving Items by Index Key
</td>
</tr>
</table>
</div>
</body>
</html>
|
