Package scriptella.core

Class EtlVariable

java.lang.Object

scriptella.core.EtlVariable

All Implemented Interfaces:

ParametersCallback

public class EtlVariable
extends Object
implements ParametersCallback

Represents a global etl variable available for all ETL file elements.

The variable provides the following functionalities:

• Utility methods useful in JEXL expressions, e.g EtlVariable.DateUtils.format(java.util.Date, String) or EtlVariable.TextUtils.nullIf(Object, Object)
• getConnection(String) method for obtaining underlying connection objects
• getGlobals() - container for global variables shared across different parts of ETL file

As of 1.1 a new syntax is introduced based on JEXL function namespaces:

• date: namespace contains functions from EtlVariable.DateUtils, e.g. date:now()
• text: namespace contains functions from EtlVariable.TextUtils, e.g. text:ifNull()
• class: namespace contains functions from EtlVariable.ClassUtils, e.g. class:forName('java.lang.System').getProperty('java.version')

Examples

Global variables

A global variable, which is set in one part of the ETL file can be later read from other places during ETL execution:

     <query connection-id="db">
       SELECT COUNT(*) as userCount from Users
       <script connection-id="jexl">
           etl.globals['globalVar'] = userCount;
       </script>
     </query>
     <script connection-id="log">
         Global variable 'globalVar': ${etl.globals['globalVar']}
    </script>
 

Obtain a native connection to the JDBC datasource

    <script connection-id="java">
        scriptella.core.EtlVariable etl = (scriptella.core.EtlVariable)get("etl");
        java.sql.Connection c = (java.sql.Connection)((scriptella.spi.NativeConnectionProvider)etl.getConnection("db")).getNativeConnection();
        java.sql.ResultSet r = c.createStatement().executeQuery("SELECT COUNT(*) FROM Test");
        r.next();
        Object cnt = r.getObject(1);
        java.util.logging.Logger.getLogger("mylogger").info("Count: "+cnt);
    </script>
 

Since:

1.0

Author:

Fyodor Kupolov

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	EtlVariable.ClassUtils	Utility class for ETL expressions.
static class	EtlVariable.DateUtils	Utility class for ETL file expressions.
static class	EtlVariable.TextUtils	Utility class for ETL file expressions.

Field Summary

Fields

Modifier and Type	Field	Description
static final String	NAME

Constructor Summary

Constructors

Constructor	Description
EtlVariable()
EtlVariable(ParametersCallback parametersCallback, EtlContext globalContext)

Method Summary

Modifier and Type	Method	Description
EtlVariable.ClassUtils	getClazz()
Connection	getConnection(String id)	Returns the connection for the specified id, This method is convenient for cases when access to the native connection is required, e.g.
EtlVariable.DateUtils	getDate()
Map<String,Object>	getGlobals()	Getter for a global variables storage.
Object	getParameter(String name)	Accessor method for parameters available in the current execution context.
EtlVariable.TextUtils	getText()
Class	loadClass(String name)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

NAME

public static final String NAME

See Also:

• Constant Field Values

Constructor Details

EtlVariable

public EtlVariable(ParametersCallback parametersCallback,
 EtlContext globalContext)

EtlVariable

public EtlVariable()

Method Details

getDate

public EtlVariable.DateUtils getDate()

getText

public EtlVariable.TextUtils getText()

getClazz

public EtlVariable.ClassUtils getClazz()

loadClass

public Class loadClass(String name)
                throws ClassNotFoundException

Throws:

ClassNotFoundException

getParameter

public Object getParameter(String name)

Accessor method for parameters available in the current execution context. Useful for cases when variables has special symbols which cannot be referenced as normal JEXL variables, e.g. etl.getParameter('Column Name')

Specified by:

getParameter in interface ParametersCallback

Parameters:

name - parameter name.

Returns:

value of the parameter.

getGlobals

public Map<String,Object> getGlobals()

Getter for a global variables storage.

This map is shared between all etl file elements and can be used for cases when there is a need to share some state globally. It is recommended to avoid using global variables except cases when it's really beneficiary and simplifies the ETL file.

Returns:

map of global variables in the scope of ETL file.

Since:

1.1

getConnection

public Connection getConnection(String id)

Returns the connection for the specified id, This method is convenient for cases when access to the native connection is required, e.g. invoking a specific method or for a manual control over a transaction boundaries.

Note: The method should be used with caution because it might affect the flow of the ETL file execution and block some optimizations which may be added to the ETL engine in the future.

Parameters:

id - id of the required connection. Null is allowed if script has only one connection.

Returns:

connection for the specified id.

Since:

1.2