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
• If you are requesting support for wide tables from the server
• If you would like to request server support for storing character data in unichar (Unicode) columns

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

• If you would like to request support from the server for the date and time SQL datatypes

     Only Adaptive Server version 12.5.1 and later support the date and time SQL datatypes.

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

JCONNECT_VERSION connection property

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

Use JCONNECT_VERSION to specify the version setting for a specific session.You can set JCONNECT_VERSION to a value of "2," "3," "4," "5," "6," or "6.05," depending on the characteristics you want.

When referring to the version constant, use this syntax:

com.sybase.jdbcx.SybDriver.VERSION_6

Although the preferred approach is to use JCONNECT_VERSION connection property, you can alternately use constant values in SybDriver.

Use SybDriver.setVersion to set the jConnect version. The setVersion method affects the jConnect default behavior for all connections created by the SybDriver object. However, you can use the JCONNECT_VERSION connection property to set version-specific behavior for individual connections. The following code sample shows how to load the jConnect driver and set the version:

import com.sybase.jdbcx.SybDriver;
SybDriver  sybDriver = (SybDriver)
   Class.forName   ("com.sybase.jdbc3.jdbc.SybDriver").newInstance();
sybDriver.setVersion
   (com.sybase.jdbcx.SybDriver.VERSION_6);
DriverManager.registerDriver(sybDriver);

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. jConnect provides a com.sybase.jdbcx.SybDriver.VERSION_LATEST constant which can be used to ensure that you are always requesting the highest version value possible for the jConnect driver you are using. However, by setting the version to com.sybase.jdbcx.SybDriver.VERSION_LATEST, you may see behavior changes if you replace your current jConnect driver with a newer one.

CANCEL_ALL connection property

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

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");

Invoking the jConnect driver

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

• Use Class.forName as shown:
  
  

  Class.forName("com.sybase.jdbc3.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 Class.forName call 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:

  Properties sysProps = System.getProperties();
  String  drivers = "com.sybase.jdbc3.jdbc.SybDriver";
  String  oldDrivers =
  sysProps.getProperty("jdbc.drivers");
  if  (oldDrivers != null)
     drivers += ":" + oldDrivers;
   sysProps.put("jdbc.drivers",  drivers.toString());

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