Servis-Rhino 4211B Guia do Utilizador descarregar pdf (Página 80)

• WL.Server.writeJMSMessage(options)

• WL.Server.requestReplyJMSMessage(options)

SQL Adapter

The SQL adapter allows a Worklight client to execute SQL statements or stored procedures against

a back-end database. The SQL adapter encapsulates the calls to the database hiding the mechanics

of how this is achieved from the Worklight client developer.

Worklight supports DB2, Oracle and MySQL database access.

Before we dive deeper into the SQL Adapter, let us spend a little time talking about the Java JDBC

technology. JDBC is a Java specification that insulates a Java programmer from the mechanics of

interacting with a specific vendor's database implementation. For example, IBM with DB2 may

choose one style of technology, Oracle a different style and MySQL yet another style. If a Java

programmer had to accommodate different vendor characteristics, the Java applications would have

to differ for each database that could be used. JDBC insulates the programmer from that chore. It

provides an API that normalizes access. To allow for the distinctions between the DB providers,

JDBC assumes that each vendor will provide a JDBC compliant "driver". This will be Java code

built and distributed by the database vendor that allows JDBC to be able to form connections and

use the target database. Since this JDBC driver class conforms to the JDBC specification, it will

provide its half of the handshake to the database and the JDBC caller will leverage those functions.

The ability to connect to the database is only part of the insulation that JDBC provides. There will

also be configuration parameters that will need to be supplied by a client that wishes to use the

database. Such things will include the physical location of the database (local or networked) and

the name of the database to be accessed (a machine can presumably host multiple databases). Since

these configuration parameters are also vendor specific, they must be supplied when the client

wishes to connect with the target. These parameters are called the "JDBC Connection URL" as

they typically look like a web URL (though not always).

When a SQL Adapter is defined, the connection policy definition looks as follows:

We notice that there are properties specific for database access:

• Url – The JDBC Connection URL used to connect to the target database. This value will

be database provider specific.

• Driver class – The name of the JDBC driver class supplied by the DB vendor.

• User – The name of the user under which the connection to the database will be performed.

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