SQL/MX Programming Manual for Java

SQLJ Programming

HP NonStop SQL/MX Programming Manual for Java—523726-003

3-8

Connection Contexts

A connection context associates the execution of each embedded SQL statement with

a particular JDBC connection to the database. Each SQL statement in an SQLJ

executable clause is implicitly or explicitly associated with a connection context. For a

particular SQLJ program, all SQL statements that are associated with the same

connection context class, including an implicit connection context, are included in the

same profile. See Profile on page 1-12.

Currently, an SQLJ program written for SQL/MX can connect only to an SQL/MX or

SQL/MP database while running on a NonStop server. You cannot establish

connections to heterogeneous database servers while running a customized SQLJ

program on a NonStop server. However, you can establish multiple connections to a

NonStop database by using explicit connection contexts. Explicit connection contexts

have these advantages:

•

Portability of applications. See Implicit Connection Contexts on page 3-8.

•

Flexibility in processing sets of database objects because separate profiles exist

for each connection context class. See Generating a Profile for Each Connection

Context Class on page 3-17.

•

Synchronized threads in a multithreaded application. See Multithreading on

page 3-23.

Implicit Connection Contexts

If you do not specify an explicit connection context in an SQLJ program, the SQLJ

translator generates code for a default, or implicit, connection context. For SQL/MX,

the name of the default connection context is:

sqlj.runtime.ref.DefaultContext

Although SQL/MX allows implicit connection contexts for SQLJ applications, such

applications might not be portable because some SQLJ run-time environments do not

provide a default connection context. Therefore, consider using explicit connection

contexts for SQLJ applications. See Explicit Connection Contexts on page 3-8.

Explicit Connection Contexts

This subsection explains how to code an explicit connection context according to these

steps:

•

Declaring a Connection Context Class on page 3-9

•

Declaring, Initializing, and Instantiating a Connection Context Object on page 3-9

•

Associating an SQLJ Executable Clause with a Connection Context on page 3-15

It also explains how to create separate profiles and modules for specific sets of

database objects. See Generating a Profile for Each Connection Context Class on

page 3-17.