Chapter 2 Programming Information

Setting up jConnect

This section describes the tasks you need to perform before you use jConnect.

Setting the jConnect version

There are several versions of jConnect; use a version setting to determine:

• The default value of the LANGUAGE connection property.
• The version-specific features that are available.
• The default character set, if no character set is specified through the CHARSET connection property.
• The default value of the CHARSET_CONVERTER connection property.
• The default value of the CANCEL_ALL connection property, which is used to set the behavior of Statement.cancel( ), which by default cancels the object on which it is invoked and any other Statement objects that have begun to execute and are waiting for results.
• Whether you are requesting support for wide tables from the server.
• Whether you would like to request server support for storing character data in unichar (Unicode) columns.

   Only Adaptive Server Enterprise version 12.5 and later support wide tables and unichar character data.

Table 2-1 lists the version settings available and their features.

The version values are constant values from the SybDriver class. When referring to the version constant, use this syntax:

com.sybase.jdbcx.SybDriver.VERSION_5

Use SybDriver.setVersion( ) to set the jConnect version. The following code samples show how to load the jConnect driver and set the version.

For jConnect 4.x:

import  com.sybase.jdbcx.SybDriver;
SybDriver sybDriver = (SybDriver)
 	Class.forName  ("com.sybase.jdbc.SybDriver").newInstance();

sybDriver.setVersion
 	(com.sybase.jdbcx.SybDriver.VERSION_4);
DriverManager.registerDriver(sybDriver);

For jConnect 5.x:

import  com.sybase.jdbcx.SybDriver;
SybDriver sybDriver = (SybDriver)
 	Class.forName
 	("com.sybase.jdbc2.jdbc.SybDriver").newInstance();

sybDriver.setVersion
 	(com.sybase.jdbcx.SybDriver.VERSION_5);
DriverManager.registerDriver(sybDriver);

For wide table support with jConnect 4.x and 5.x:

To enable wide table support with Adaptive Server Enterprise version 12.5 and later, use SybDriver.setVersion( ) to set the jConnect version to 6:

sybDriver.setVersion
 	(com.sybase.jdbcx.SybDriver.VERSION_6);

You can call setVersion( ) multiple times to change the version setting. New connections inherit the behavior associated with the version setting at the time the connection was made. Changing the version setting during a session does not affect the current connection.

As described in the next section, you can use JCONNECT_VERSION to override the SybDriver version setting and specify a different version setting for a specific connection.

JCONNECT_VERSION connection property

Use JCONNECT_VERSION to specify the version setting for a specific session.You can set JCONNECT_VERSION to an integer value of "2," "3," "4," "5," or "6" depending on the characteristics you want (see Table 2-1).

CANCEL_ALL connection property

CANCEL_ALL is a Boolean-valued connection property for specifying the behavior of the Statement.cancel( ) method.

   In jConnect version 4.0 and earlier, the default for CANCEL_ALL is true. In jConnect version 4.1 and later, to comply with the JDBC specification, if you set the connection property JCONNECT_VERSION to "4" or above, the default setting for CANCEL_ALL is false.

The settings for CANCEL_ALL have the following effect on Statement.cancel( ):

• If CANCEL_ALL is false, invoking Statement.cancel( ) cancels only the Statement object it is invoked on. Thus, if stmtA is a Statement object, stmtA.cancel( ) cancels the execution of the SQL statement contained in stmtA in the database, but no other statements are affected. stmtA is canceled whether it is in cache waiting to execute or has started to execute and is waiting for results.
• If CANCEL_ALL is true, invoking Statement.cancel( ) cancels not only the object it is invoked on, but also any other Statement objects on the same connection that have executed and are waiting for results.

The following example sets CANCEL_ALL to false. In the example, props is a Properties object for specifying connection properties.

...
 props.put("CANCEL_ALL",  "false");

   To cancel the execution of all Statement objects on a connection, regardless of whether or not they have begun execution on the server, use the extension method SybConnection.cancel( ).

Invoking the jConnect driver

To register and invoke the Sybase jConnect driver, use either of two suggested methods:

For jConnect 4.x:

Class.forName("com.sybase.jdbc.SybDriver").newInstance();

For jConnect 5.x:

Class.forName("com.sybase.jdbc2.jdbc.SybDriver").newInstance();

Add the jConnect driver to the jdbc.drivers system property. At initialization, the DriverManager class attempts to load the drivers listed in jdbc.drivers. This is less efficient than the previous approach. You can list multiple drivers in this property, separated with a colon (:). The following code samples show how to add a driver to jdbc.drivers within a program:

For jConnect 4.x:

Properties sysProps = System.getProperties();
String  drivers = "com.sybase.jdbc.SybDriver";
String  oldDrivers =
sysProps.getProperty("jdbc.drivers");
if  (oldDrivers != null)
   drivers += ":" + oldDrivers;
sysProps.put("jdbc.drivers",  drivers.toString());

For jConnect 5.x:

Properties sysProps = System.getProperties();
String  drivers = "com.sybase.jdbc2.jdbc.SybDriver";
String  oldDrivers =
sysProps.getProperty("jdbc.drivers");
if  (oldDrivers != null)
   drivers += ":" + oldDrivers;
 sysProps.put("jdbc.drivers",  drivers.toString());

   System.getProperties( ) is not allowed for Java applets. Use the
Class.forName( ) method, instead.

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