Business Process and Data Transformation Language Reference
<catch>
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Catch a fault produced by a <throw> element.
Synopsis
<scope>
  <throw fault='"MyFault"'/>
        ...
  <faulthandlers>
    <catch fault='"MyFault"'>
          ...
    </catch>
  </faulthandlers>
</scope>
Details
Attribute or Element Description Value
fault attribute Required. The name of the fault. It can be a literal text string or an expression to be evaluated. A string of 0 to 255 characters. If this is an expression, it must use the scripting language specified by the containing <process> element.
name, disabled, xpos, ypos, xend, yend attribute See Common Attributes and Elements.”  
<annotation> element
Other elements Optional. <catch> may contain zero or more of the following elements in any combination: <alert>, <assign>, <branch>, <break>, <call>, <code>, <compensate>, <continue>, <delay>, <empty>, <foreach>, <if>, <label>, <milestone>, <reply>, <rule>, <scope>, <sequence>, <sql>, <switch>, <sync>, <throw>, <trace>, <transform>, <until>, <while>, <xpath>, or <xslt>.  
Description
When a <throw> statement executes, control immediately shifts to the <faulthandlers> block inside the same <scope>, skipping all intervening statements after the <throw>. Inside the <faulthandlers> block, the program attempts to find a <catch> block whose value attribute matches the fault string expression in the <throw> statement. This comparison is case-sensitive. When you specify a fault string it needs the extra set of quotes to contain it, as shown below:
<catch fault='"thrown"'/>
If there is a <catch> block that matches the fault, the program executes the code within this <catch> block and then exits the <scope>. The program resumes execution at the next statement following the closing </scope> element.
If a fault is thrown, and the corresponding <faulthandlers> block contains no <catch> block that matches the fault string, control shifts from the <throw> statement to the <catchall> block inside <faulthandlers>. After executing the contents of the <catchall> block, the program exits the <scope>. The program resumes execution at the next statement following the closing </scope> element. It is good programming practice to ensure that there is always a <catchall> block inside every <faulthandlers> block, to ensure that the program catches any unanticipated errors.
For details, see BPL Error Handling Conventions in Developing BPL Processes.
Note:
If a <catchall> is provided, it must be the last statement in the <faulthandlers> block. All <catch> blocks must appear before <catchall>.
See Also
<catchall>, <compensate>, <compensationhandlers>, <faulthandlers>, <scope>, and <throw>.