Encapsulates a transaction.
<dsp:demaracateTransaction var-spec>
...
</dsp:demaracateTransaction>Attributes
var-spec
Defines an EL variable or scripting variable with one of these attributes:
Attribute | Description |
|---|---|
| Names an EL variable. When you use |
| Names a scripting variable that scriptlets and expressions can access at runtime. |
The variable has three properties:
success: A Boolean property, specifies the status of transaction. A call toisSuccessobtains the property’s setting:true: The start and commit operations succeeded.false: The start or commit operation failed.
exception: Identifies theThrowableexception object produced when a transaction fails to start properly. A call togetExceptionreturns the exception object.commitException: Identifies theThrowableexception object produced when a transaction fails to commit. A call togetCommitExceptionreturns the exception object
Usage Notes
The dsp:demarcateTransaction tag manages a transaction by starting it, checking it for errors, committing the transaction if no errors exist, and rolling back the transaction if errors occur. This tag creates a variable whose properties—success, exception, and commitException—indicate the status of the transaction.
Note: An error might occur if dsp:demarcateTransaction starts execution when another transaction is in progress.
Example
The following example assumes the following conditions are true:
currentStudentis a page parameter that is set while a servlet bean iterates through all students in a class.A mechanism exists to consecutively save each student’s grade to the
currentGradepage parameter.
<dsp:importbean bean="\atg\samples\Student_01" var="student"/>
<dsp:importbean bean="\atg\samples\Algebra" />
<dsp:demarcateTransaction var="demarcateXA">
<dsp:setvalue bean="Algebra.class.student" value="${student.name}"/>
<dsp:setvalue bean="Algebra.class.grade" value="${student.grade}"/>
<c:if test="${!demarcateXA.success}">
The grade could not be processed. Here's why:
<c:choose>
<c:when value="${!empty demarcateXA.exception}"/>
<c:out value="${demarcateXA.exception}"/>
<c:when value="${!empty demarcateXA.commitException}"/>
<c:out value="${demarcateXA.commitException}"/>
</c:choose>
</c:if>
</dsp:demarcateTransaction>In this example, the transaction encapsulates the tasks required to save the grades provided to students in a class. The transaction ensures that student names and grades are added to Algebra.Student_01 at the same time. If the transaction fails, no name or grade is saved; instead, the appropriate message displays for the exception or commitException exceptions.
