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
|
/*
* Copyright 2006-2012 Amazon Technologies, Inc. or its affiliates.
* Amazon, Amazon.com and Carbonado are trademarks or registered trademarks
* of Amazon Technologies, Inc. or its affiliates. All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.amazon.carbonado.repo.jdbc;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.NoSuchElementException;
import com.amazon.carbonado.FetchException;
import com.amazon.carbonado.Storable;
import com.amazon.carbonado.cursor.AbstractCursor;
import com.amazon.carbonado.txn.TransactionScope;
/**
* Cursor implementation that queries a PreparedStatement.
*
* @author Brian S O'Neill
*/
class JDBCCursor<S extends Storable> extends AbstractCursor<S> {
private final JDBCStorage<S> mStorage;
private final TransactionScope<JDBCTransaction> mScope;
private final Connection mConnection;
private final PreparedStatement mStatement;
private ResultSet mResultSet;
private boolean mHasNext;
/**
* @throws SQLException from executeQuery on statement. Caller must clean
* up when this happens by closing statement and connection.
*/
JDBCCursor(JDBCStorage<S> storage,
TransactionScope<JDBCTransaction> scope,
Connection con,
PreparedStatement statement)
throws SQLException
{
mStorage = storage;
mScope = scope;
mConnection = con;
mStatement = statement;
mResultSet = statement.executeQuery();
scope.register(storage.getStorableType(), this);
}
public void close() throws FetchException {
if (mResultSet != null) {
try {
mScope.unregister(mStorage.getStorableType(), this);
mResultSet.close();
mStatement.close();
mStorage.mRepository.yieldConnection(mConnection);
} catch (SQLException e) {
throw mStorage.getJDBCRepository().toFetchException(e);
} finally {
mResultSet = null;
mHasNext = false;
}
}
}
public boolean hasNext() throws FetchException {
ResultSet rs = mResultSet;
if (rs == null) {
return false;
}
if (!mHasNext) {
try {
mHasNext = rs.next();
} catch (SQLException e) {
try {
close();
} catch (FetchException e2) {
// Don't care.
}
throw mStorage.getJDBCRepository().toFetchException(e);
}
if (!mHasNext) {
close();
}
}
return mHasNext;
}
public S next() throws FetchException, NoSuchElementException {
if (!hasNext()) {
throw new NoSuchElementException();
}
try {
S obj = mStorage.instantiate(mResultSet);
mHasNext = false;
return obj;
} catch (SQLException e) {
try {
close();
} catch (FetchException e2) {
// Don't care.
}
throw mStorage.getJDBCRepository().toFetchException(e);
}
}
@Override
public int skipNext(int amount) throws FetchException {
if (amount <= 0) {
if (amount < 0) {
throw new IllegalArgumentException("Cannot skip negative amount: " + amount);
}
return 0;
}
int actual = 0;
while (amount > 0) {
if (hasNext()) {
actual++;
amount--;
mHasNext = false;
} else {
break;
}
}
return actual;
}
}
|
