Jaybird 2.1 JDBC driver Java Programmer's Manual - Firebird

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• First, instead of using the one statement object we have to use three – one per statement. • Second, before executing the statement we have to set parameters first. As it is showed on the example, parameters are referenced by their position. The PreparedStatement interface provides setter methods for all primitive types in Java as well as for some widely used SQL data types (BLOBs, CLOBs, etc.). The NULL value is set by calling the PreparedStatement.setNull(int) method. • Third, we are forced now to use three nested try/finally blocks, which makes code less readable. So, where's the advantage? First of all, we can redesign our application to prepare those statements before calling that code (for example in a constructor) and close them when application is shut down. In this case the code is even more compact (see Illustration 4.5). Unfortunately the application is now responsible for prepared statement management. When connection is closed, the prepared statement object will be invalidated, but the application will not be notified about this fact. Also, if the application uses similar statements in different parts of the application, the refactoring might affect many classes, possibly destabilizing the Chapter 4. Executing statements 40
code. So, the refactoring on the Illustration 4.5 is not something we want to do. // prepared statement management PreparedStatement queryStmt = connection.prepareStatement(queryStr); PreparedStatement updateStmt = connection.prepareStatement(updateStr); PreparedStatement insertStmt = connection.prepareStatement(insertStr); ...................... // query management queryStmt.clearParameters(); queryStmt.setString(1, "Doe"); queryStmt.setString(2, "Joe"); ResultSet rs = queryStmt.executeQuery(); if (rs.next()) { int userId = rs.getInt(1); } updateStmt.clearParameters(); updateStmt.setInt(1, userId); int rowsUpdated = updateStmt.executeUpdate(); if (rowsUpdated == 0) { insertStmt.clearParameters(); insertStmt.setInt(1, userId); rowsUpdated = insertStmt.executeUpdate(); if (rowsUpdated != 1) throw new SomeException( "User was not updated correctly."); ...................... // prepared statement cleanup insertStmt.close(); updateStmt.close(); queryStmt.close(); Illustration 4.5: Rewritten example to let application manage prepared statements The answer to the advantage question is hidden in the prepareStatement(String) call. Since the same statement can be used for different parameter values, connection object has a possibility to perform prepared statement caching. JDBC driver can ignore the request to close the prepared statement, save it internally and reuse it each time application asks to prepare an SQL statement that is known to the connection. Prepared statement pooling As it was mentioned before, connection pooling was introduced to reduce the time needed to obtain a connection. Despite its rich features, the operation of obtaining new connection in Firebird is cheap – usually connection pooling in an application that heavily opens and closes connection brings ~5% of performance. However there is one more way to speed the application. Execution of statements in Firebird always happens in three steps: Chapter 4. Executing statements 41
Page 1 and 2: Jaybird 2.1 JDBC driver Java Progra
Page 3 and 4: Table Of Contents Table of Contents
Page 5 and 6: 1. Introduction Chapter 1. Jaybird
Page 7 and 8: Specification Details JDBC 3.0 Driv
Page 9 and 10: 2. Obtaining a connection Chapter 2
Page 11 and 12: uns. On Windows it must include the
Page 13 and 14: this purpose showed on Illustration
Page 15 and 16: jdbc:firebirdsql:embedded: jdbc:fir
Page 17 and 18: will close the physical connection
Page 19 and 20: Illustration 2.10 Shows how to acce
Page 21 and 22: Chapter 2. Obtaining a connection 2
Page 23 and 24: checking the error code which is se
Page 25 and 26: application will always use the min
Page 27 and 28: Constant name Constant value SQL_ST
Page 29 and 30: collation. isc_dsql_command_err "In
Page 31 and 32: 4. Executing statements Chapter 4.
Page 33 and 34: It is also allowed to use the same
Page 35 and 36: Statement behind the scenes The exa
Page 37: dynamics” chapter, it allows to g
Page 41 and 42: Therefore, if structure modificatio
Page 43 and 44: CREATE PROCEDURE factorial( max_val
Page 45 and 46: PreparedStatement stmt = connection
Page 47 and 48: import java.sql.*; import org.fireb
Page 49 and 50: Using batch updates with a prepared
Page 51 and 52: 5. Working with result sets Chapter
Page 53 and 54: Note, current implementation does n
Page 55 and 56: Statement selectStmt = connection.c
Page 57 and 58: 1 2 3 4 Connection connection = ...
Page 59 and 60: 1 2 3 Statement selectStmt = connec
Page 61 and 62: ead-committed mode sees all committ
Page 63 and 64: FirebirdConnection fbConnection = (
Page 65 and 66: Read-committed Concurrency Consiste
Page 67 and 68: 7. Working with Services Chapter 7.
Page 69 and 70: e created, use addBackupPath(String
Page 71 and 72: specified via the properties of thi
Page 73 and 74: Constant Description RESTORE_ONE_AT
Page 75 and 76: The database shutdown is performed
Page 77 and 78: gfix -mend command. After this oper
Page 79 and 80: Method Description ● PAGE_FILL_RE
Page 81 and 82: It can also happen that multiple tr
Page 83 and 84: EventManager eventManager = new FBE
Page 85 and 86: DPB Parameter and its Alias(es) isc
Page 87 and 88: JDBC Type Firebird Type Java Object
Page 89 and 90:
This group of properties are specif
Page 91 and 92:
specialized use, because there's no
Page 93 and 94:
Firebird uses following algorithm w
Page 95 and 96:
It is clear that the conversion usi
Page 97 and 98:
Firebird encoding Java encoding Siz
Page 99 and 100:
JDBC Jaybird built-in UDF mode Nume
Page 101 and 102:
JDBC Jaybird REPLACE(strin g1, stri
Page 103:
JDBC Jaybird (interval, timestamp1,
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Jaybird 2.1 JDBC driver Java Programmer's Manual - Firebird

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