<throw>

Syntax

<scope>
   <throw fault='"MyFault"'/>
         ...
   <faulthandlers>
     <catch fault='"MyFault"'>
           ...
     </catch>
   </faulthandlers> 
</scope>

Details

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:

<throw 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 “Handling Errors in BPL” in Developing BPL Processes.

See Also

<catch>, <catchall>, <compensate>, <compensationhandlers>, <faulthandlers>, and <scope>.