org.outerj.expression
Class NVLFunction
java.lang.Object
org.outerj.expression.AbstractExpression
org.outerj.expression.NVLFunction
- All Implemented Interfaces:
- Expression
- public class NVLFunction
- extends AbstractExpression
A function for substitution of values that cannot be evaluated. For instance,
referring to a variable that was created in an earler step but assigned no value
causes an ExpressionException to be thrown when the expression is evaluated. The
following example illustrates typical usage:
<flow>
<step id="getParameters">
<interaction>
<parameter id="request_id" required="false">
<prompt>Please Enter Request ID</prompt>
<title>Request ID</title>
<type base="string" />
</parameter>
</interaction>
</step>
</flow>
<output>
<http host="deathstar.mcao.maricopa.gov" port="80" path="/xprototype/tasks">
<parameter name='request_id' expression='NVL(request_id, "")'/>
</http>
</output>
Method Summary |
void |
check()
Check that two arguments have been provided, and that the second one is not null. |
java.lang.Object |
evaluate(ExpressionContext context)
Replace expr1 with expr2 when expr1 is null or otherwise cannot be evaluated. |
java.lang.String |
getDescription()
Returns a description of this expression that will be shown to the user
in error messages. |
java.lang.Class |
getResultType()
Returns the class of the the type of object that this expression will return. |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
NVLFunction
public NVLFunction()
evaluate
public java.lang.Object evaluate(ExpressionContext context)
throws ExpressionException
- Replace expr1 with expr2 when expr1 is null or otherwise cannot be evaluated.
Usage: NVL(expr1, expr2)
- Throws:
ExpressionException
getResultType
public java.lang.Class getResultType()
- Description copied from interface:
Expression
- Returns the class of the the type of object that this expression will return.
This allows to check the correctness of functions at compile-time.
If unknown, this may return
null
.
getDescription
public java.lang.String getDescription()
- Description copied from interface:
Expression
- Returns a description of this expression that will be shown to the user
in error messages.
check
public void check()
throws ExpressionException
- Check that two arguments have been provided, and that the second one is not null.
- Specified by:
check
in interface Expression
- Overrides:
check
in class AbstractExpression
- Throws:
ExpressionException