|
1
28
29 package com.caucho.db.sql;
30
31 import com.caucho.db.Database;
32 import com.caucho.db.store.Transaction;
33 import com.caucho.db.table.TableIterator;
34 import com.caucho.log.Log;
35 import com.caucho.sql.SQLExceptionWrapper;
36
37 import java.io.IOException  ;
38 import java.sql.SQLException ;
39 import java.util.logging.Logger ;
40
41 public class ExistsQuery extends SelectQuery {
42 private static final Logger log = Log.open(ExistsQuery.class);
43
44 private static Expr []_nullExprs = new Expr[0];
45
46 protected ExistsQuery(Database db, String sql)
47 throws SQLException
48 {
49 super(db, sql);
50 }
51
52
55 public boolean exists(QueryContext context, Transaction xa)
56 throws SQLException
57 {
58 SelectResult result = SelectResult.create(_nullExprs, null);
59
60 try {
61 TableIterator []rows = result.initRows(getFromItems());
62 context.init(xa, rows, isReadOnly());
63
64 return execute(result, rows, context, xa);
65 } catch (IOException e) {
66 throw new SQLExceptionWrapper(e);
67 } finally {
68 context.unlock();
69
70 result.close();
71 }
72 }
73
74
77 private boolean execute(SelectResult result,
78 TableIterator []rows,
79 QueryContext context,
80 Transaction transaction)
81 throws SQLException , IOException
82 {
83 FromItem []fromItems = getFromItems();
84 int rowLength = fromItems.length;
85
86 return start(rows, rowLength, context, transaction);
87 }
88
89
92 public void execute(QueryContext queryCtx, Transaction xa)
93 throws SQLException
94 {
95 throw new UnsupportedOperationException ();
96 }
97 }
98 |
Popular Tags |
Java API By Example, From Geeks To Geeks.