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You can design processes so that they gracefully handle
errors when they occur:
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Use the Variable Logger service to monitor process data
at run time.
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Use event catches to handle execution errors.
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Use the Stall service to suspend execution when undesirable
situations occur.
Execution errors
An execution error causes a process instance
to stall. A process instance fails to complete processing for one
of these reasons:
Stalled operation errors
A stalled operation error occurs when
an operation in your process version fails during execution. For
example, the execute operation from the Set Value service tries
to assign a string value to a process variable of the float data
type. This value is not valid and causes the operation to stall.
Stalled branch errors
A stalled branch error occurs when a routing
condition has an error. For example, you may have a condition on
a route that uses a value from a form. The route condition is based
on a numeric value, but the form value is inadvertently entered
as a string value. This error causes the branch to stall.
You
can view the list and details of stalled operation errors or stalled
branch errors from within administration console. You will see the
name of the operation or branch that is stalled, and you can view
the details of the trace back that may provide useful information
to identify the source of the problem.
Implementation errors
Implementation errors occur when a process version completes
execution successfully, but it does not work as it was designed.
For example, if you have a route condition to route all high-risk
loan applications to the manager, and the manager never gets routed
any of these loan applications, you have an error in your process
version. The two types of implementation errors are computational and
situational.
Computational errors
Computational errors occur when the execution
of a command results in an error. For example, an error can occur
in a routing condition when the function in an expression uses a
parameter of the wrong data type. When the error occurs, the branch
or action involved is stalled until the AEM forms administrator
intervenes. The type of branch that your process version uses can
mitigate the effects of computational errors.
Situational errors
Situational errors occur when an issue that should
not occur does occur during the execution of a process version,
even though the process version behaved as designed. For example,
a process version assigns a task to a random user in a specific
user group. If that user does not complete the task by a certain
time, it is incorrectly reassigned to the same user in the group
again.
A situational error occurs if the task was reassigned
to the same person. To avoid situational errors, you can cause the
branch to stall before the situation occurs. The administrator can
then intervene and attempt to correct the situation.
Monitoring variables using the Variable Logger service
Use the log operation
that the Variable Logger service provides to monitor the values
of process variables at run time in a production environment. The
Log operation writes variable values to a file, to standard out,
or to the AEM forms Server log at a specific point in the process.
For example, the following process diagram includes a log operation
after an Assign Task operation. After the log operation, an execute
operation from the Set Value service manipulates the data that the
Assign Task operation captures. The log operation saves variable
data to a file. If the execute operation stalls at run time, the
logged variable values can be used to troubleshoot the error.
The log operation reports the following information for each
variable in the process:
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The name of the variable, as an XPath expression
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The data type of the variable
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The value of the variable
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The process identification (PID) of the process instance
in which the log operation executed.
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The operation identification (ActionID) of the log operation.
The following text is an example log entry that a log operation
named log3 provides. The log3 operation has an ActionID of 37, and
was executed in a process instance with PID 13. The process includes
the two variables named numberVar and listVar:
[PID:13] [ActionID:37] Action Name: "log3" Start...
[PID:13] /process_data/@numberVar - java.lang.Float: 100000.0
[PID:13] /process_data/@listVar: null
[PID:13] [ActionID:37] End!
For more information about the log operation, see
log operation
.
Handling errors using exception event catches
Exception event catches enable
processes to react to errors that occur when an operation executes.
For example, when an exception event is caught, the process can
write information to a log file, or send an email to the AEM forms
administrator. (See also
Catching event throws
.)
The following process diagram uses a Remove PDF Password Encryption operation
to decrypt a PDF document, and then saves the document to the hard drive
using the Write Document operation. If an EncyrptionServiceException exception
occurs when the document is being decrypted, the Send With Document
operation sends an email to notify the administrator.
Handling situational errors using the Stall service
Use the execute operation that
the Stall service provides to prevent situational errors that you
anticipate.
For example, processes can use data that is provided from an
external resource, such as a partner’s database. The
executeScript
operation
from the
Execute Script
service
can be used to verify that the data is valid. If the data is not
valid, the Execute operation from the Stall service can stall the
process instance while the data in the database is corrected.
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For information about viewing variable values
during testing, see
