Using the SQL Outbound Adapter

Using SQL Adapters with Ensemble

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Ensemble Adapter and Gateway Guides > Using SQL Adapters with Ensemble > Using the SQL Outbound Adapter

This chapter describes the default behavior of the Ensemble SQL outbound adapter (EnsLib.SQL.OutboundAdapter) and describes how to use this adapter in your productions. It discusses the following topics:

Default Behavior

Within a production, an outbound adapter is associated with a business operation that you create and configure. The business operation receives a message from within the production, looks up the message type, and executes the appropriate method. This method usually executes methods of the associated adapter.

The SQL outbound adapter (EnsLib.SQL.OutboundAdapter) provides settings that you use to specify the data source to connect to and any login details needed for that data source. It also provides methods to perform common SQL activities such as the following:

Executing queries
Executing stored procedures
Performing inserts, updates, and deletes

Creating a Business Operation to Use the Adapter

To create a business operation to use the EnsLib.SQL.OutBoundAdapter, you create a new business operation class. Later, add it to your production and configure it.

You must also create appropriate message classes, if none yet exist. See “Defining Ensemble Messages” in Developing Ensemble Productions.

The following list describes the basic requirements of the business operation class:

Your business operation class should extend Ens.BusinessOperation.
The ADAPTER parameter should equal EnsLib.SQL.OutboundAdapter.
The INVOCATION parameter should specify the invocation style you want to use, which must be one of the following.
- Queue means the message is created within one background job and placed on a queue, at which time the original job is released. Later, when the message is processed, a different background job will be allocated for the task. This is the most common setting.
- InProc means the message will be formulated, sent, and delivered in the same job in which it was created. The job will not be released to the sender’s pool until the message is delivered to the target. This is only suitable for special cases.
Your class should define a message map that includes at least one entry. A message map is an XData block entry that has the following structure:
```
XData MessageMap
{
<MapItems>
  <MapItem MessageType="messageclass">
    <Method>methodname</Method>
  </MapItem>
  ...
</MapItems>
}
```
Your class should define all the methods named in the message map. These methods are known as message handlers. In general, these methods will refer to properties and methods of the Adapter property of your business operation.
For other options and general information, see “Defining a Business Operation Class” in Developing Ensemble Productions.

The following example shows the general structure that you need:

Class ESQL.NewOperation1 Extends Ens.BusinessOperation 
{
Parameter ADAPTER = "EnsLib.SQL.OutboundAdapter";

Parameter INVOCATION = "Queue";

Method SampleCall(pRequest As Ens.Request, Output pResponse As Ens.Response) As %Status
{
  Quit $$$ERROR($$$NotImplemented)
}

XData MessageMap
{
<MapItems>
  <MapItem MessageType="Ens.Request">
    <Method>SampleCall</Method>
  </MapItem>
</MapItems>
}
}

Note:

Studio provides a wizard that you can use to create a stub similar to the preceding. To access this wizard, click New on the File menu and then click the Production tab. Choose to create a business operation and select EnsLib.SQL.OutboundAdapter as the associated outbound adapter.

Creating Methods to Perform SQL Operations

When you create a business operation class for use with EnsLib.SQL.OutboundAdapter, typically your biggest task is writing message handlers, that is, methods to perform various SQL operations. In general, these methods will refer to properties and methods of the Adapter property of your business operation. For example:

 set tSC = ..Adapter.ExecuteUpdate(.numrows,sql)

A method might look like the following.

/// Insert into NewCustomer table
Method Insert(pReq As ESQL.request, Output pResp As ESQL.response1) As %Status
{
 kill pResp
 set pResp=$$$NULLOREF

 set sql="insert into NewCustomer (Name,SSN,City,SourceID) values (?,?,?,?)"

 //perform the Insert
 set tSC = ..Adapter.ExecuteUpdate
   (.nrows,sql,pReq.Name,pReq.SSN,pReq.City,pReq.CustomerID)

 //create the response message
 set pResp=##class(ESQL.response1).%New()
 set pResp.AffectedRows=nrows

 if 'tSC write " failed ",tSC quit tSC
 quit 1
}

To create these methods, you should become familiar with the methods and properties of the EnsLib.SQL.OutboundAdapter class. The chapter “Creating Adapter Methods for SQL” provides more detail about these tools.

Handling Multiple SQL Statements per Message

The adapter configuration is designed to deal with the simple case where the business operation executes one SQL statement per message it receives. If your business operation needs to execute multiple SQL statements for a given message, use the following style (or similar) in your OnMessage() method:

OnMessage(..)
{
    Set tStayConn=..Adapter.StayConnected
    Set ..Adapter.StayConnected=-1
 
    //... your ..Adapter SQL Operations here...
 
   Set ..Adapter.StayConnected=tStayConn
   If 'tStayConn&&..Adapter.Connected Do ..Adapter.Disconnect()
   Quit tSC
}

Adding and Configuring the Business Operation

To add your business operation to an Ensemble production, use the Management Portal to do the following:

Add an instance of your custom business operation class to the Ensemble production.
Enable the business operation.
Configure the adapter to communicate with a specific external data source. Specifically:
- Specify the data source to which the adapter should connect
- Use other common runtime settings for your production
Run the production.

Specifying the Data Source Name

The EnsLib.SQL.OutboundAdapter provides a runtime setting that you use to specify the data source that you want to connect to. When you configure the business operation, you should set an appropriate initial value for this setting:

DSN

This data source name specifies the external data source to which to connect. Ensemble distinguishes between these three forms automatically: a defined Caché SQL Gateway connection, a JDBC URL, or an ODBC DSN configured in your operating system.

If this name matches the name of a JDBC or ODBC connection configured from the [Home] > [Configuration] > [Object/SQL Gateway Settings] page of the Management Portal, Ensemble uses the parameters from that specification. If the entry is not the name of a configured connection and it contains a colon (:), it assumes a JDBC URL, otherwise it assumes an ODBC DSN.

If this data source is protected by a password, create Ensemble credentials to contain the username and password. Then set the Credentials setting equal to the ID of those credentials; see “Specifying Other Runtime Settings” for details.

If you are using a JDBC data source, the following settings also apply:

JGService

Configuration name of the Java Gateway service controlling the Java Gateway server this operation uses.

Important:

This setting is required for all JDBC data sources, even if you are using a working SQL gateway connection with JDBC. For JDBC connections to work, a business service of type EnsLib.JavaGateway.Service must be present. The SQL adapter requires the name of this configuration item and uses its configured settings to connect to the JVM it manages.

JDBCDriver

JDBC driver class name.

If you use a named SQL Gateway Connection as DSN, this value is optional; but if present, it overrides the value specified in the named JDBC SQL Gateway Connection set of properties.

JDBCClasspath

Classpath for JDBC driver class name, if needed in addition to the ones configured in the Java Gateway Service.

ConnectionAttributes

An optional set of SQL connection attribute options. For ODBC, they have the form:

attr :val ,attr :val

For example, AutoCommit:1.

For JDBC, they have the form

attr =val ;attr =val

For example, TransactionIsolationLevel=TRANSACTION_READ_COMMITTED.

If you use a named JDBC SQL Gateway Connection as DSN, this value is optional; but if present, it overrides the value specified in the named JDBC SQL Gateway Connection set of properties.

Specifying Other Runtime Settings

The EnsLib.SQL.OutboundAdapter provides the following additional runtime settings:

Credentials

ID of the Ensemble credentials that can authorize a connection to the given DSN. For information on creating Ensemble credentials, see Configuring Ensemble Productions.

StayConnected

Specifies whether to keep the connection open between commands, such as issuing an SQL statement or changing an ODBC driver setting.

If this setting is 0, the adapter disconnects immediately after each command.
If this setting is positive, it specifies the idle time, in seconds, after the command completes. The adapter disconnects after this idle time.
If this setting is –1, the adapter auto-connects on startup and then stays connected.

If you are managing database transactions as described in “Managing Transactions,” later in this book, do not set StayConnected to 0.

For any settings not listed here, see Configuring Ensemble Productions.