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
|
/*-
* Copyright (c) 2002,2009 Oracle. All rights reserved.
*
*/
package db;
import com.sleepycat.db.*;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.InputStreamReader;
import java.io.IOException;
import java.io.PrintStream;
class SecondaryExample
{
private static final String progname = "SecondaryExample";
private static final String DATABASE_HOME = "TESTDIR";
public static void main(String[] args)
{
try {
SecondaryExample app = new SecondaryExample();
app.run();
} catch(Exception e) {
System.err.println(progname + ": " + e);
e.printStackTrace(System.err);
System.exit(1);
}
}
void run() throws DbException, FileNotFoundException
{
DbEnv dbenv = new DbEnv(0);
/* Open the environment. */
dbenv.open(DATABASE_HOME,
Db.DB_CREATE | Db.DB_INIT_LOCK | Db.DB_INIT_LOG |
Db.DB_INIT_MPOOL | Db.DB_INIT_TXN, 0);
try {
run_app(dbenv);
} finally {
dbenv.close(0);
}
}
private void run_app(DbEnv dbenv)
throws DbException, FileNotFoundException
{
Db dbp, sdbp;
Dbt key, pkey, skey, data;
StudentRecord srec;
/* Open/create primary */
dbp = new Db(dbenv, 0);
dbp.open(null, "students.db", null, Db.DB_BTREE, Db.DB_CREATE,
0600);
/*
* Open/create secondary. Note that it supports duplicate data
* items, since last names might not be unique.
*/
sdbp = new Db(dbenv, 0);
sdbp.set_flags(Db.DB_DUP | Db.DB_DUPSORT);
sdbp.open(null, "lastname.db", null, Db.DB_BTREE, Db.DB_CREATE,
0600);
try {
/* Associate the secondary with the primary. */
dbp.associate(sdbp, new GetName(), 0);
/* Add a new record */
key = new Dbt();
key.set_data("WC42".getBytes());
key.set_size(4);
srec = new StudentRecord();
srec.student_id = "WC42";
srec.last_name = "Churchill ";
srec.first_name = "Winston ";
data = new Dbt();
srec.encode(data);
System.out.println("Adding a record with primary key " +
new String(key.get_data()) + " and secondary key " +
srec.last_name);
dbp.put(null, key, data, 0);
/* Now do a lookup */
skey = new Dbt();
pkey = new Dbt();
data = new Dbt();
skey.set_data("Churchill ".getBytes());
skey.set_size(15);
System.out.println("Searching with secondary key " +
new String(skey.get_data()));
sdbp.pget(null, skey, pkey, data, 0);
System.out.println("Found a record with primary key " +
new String(pkey.get_data()));
} finally {
dbp.close(0);
sdbp.close(0);
}
}
/*
* getname -- extracts a secondary key (the last name) from a primary
* key/data pair
*/
class GetName implements DbSecondaryKeyCreate {
public int secondary_key_create(Db secondary,
Dbt pkey, Dbt pdata, Dbt skey) {
StudentRecord srec = new StudentRecord();
srec.decode(pdata);
// Make a fixed-length array of last_name
byte[] last_name_data = srec.last_name.getBytes();
byte[] last_name_raw = new byte[15];
System.arraycopy(last_name_data, 0, last_name_raw, 0,
last_name_data.length);
skey.set_data(last_name_raw);
skey.set_size(last_name_raw.length);
return (0);
}
}
class StudentRecord
{
String student_id; // assumed to be 4 bytes long
String last_name; // assumed to be 15 bytes long
String first_name; // assumed to be 15 bytes long
void decode(Dbt dbt) {
byte[] data = dbt.get_data();
student_id = new String(data, 0, 4);
last_name = new String(data, 4, 15);
first_name = new String(data, 19, 15);
}
void encode(Dbt dbt) {
byte[] data = new byte[34];
System.arraycopy(student_id.getBytes(), 0, data, 0, 4);
byte[] last_name_raw = last_name.getBytes();
System.arraycopy(last_name_raw, 0, data, 4,
last_name_raw.length);
byte[] first_name_raw = first_name.getBytes();
System.arraycopy(first_name_raw, 0, data, 19,
first_name_raw.length);
dbt.set_data(data);
dbt.set_size(data.length);
}
}
}
|
