Effective Error and Exception Handling in X++: Best Practices and Techniques

What is Exception handling?

Exception handling is a programming language construct or mechanism designed to handle the occurrence of exceptions, which are unusual or error conditions that can disrupt the normal flow of program execution. The primary goal of exception handling is to provide a structured and controlled way to manage errors, ensuring that the program can recover gracefully or terminate in a controlled manner. Here are the key concepts and components of exception handling:

Key Concepts

1. Exception: An event that occurs during the execution of a program that disrupts the normal flow of instructions. Examples include division by zero, file not found, and invalid input.

2. Exception Handling Block: A block of code designed to handle exceptions, usually consisting of try, catch (or except in some languages), and optionally finally.

Components

1. Try Block: This block contains the code that may cause an exception. The program executes this block and monitors for any exceptions.

2. Catch Block (Except Block): This block is executed if an exception occurs in the try block. It contains code to handle the exception.
3. Finally Block: This block is optional and contains code that will run regardless of whether an exception was thrown or not. It is often used for cleanup activities, such as closing files or releasing resources.

How do you handle errors and exceptions in X++?

Handling errors and exceptions in X++ is an important aspect of developing robust and reliable applications. Here are some ways to handle errors and exceptions in X++:

1. Try-Catch blocks: You can use try-catch blocks to handle exceptions that might be thrown by your code. The try block contains the code that might throw an exception, while the catch block contains the code to handle the exception.

try
{
 // code that might throw an exception
}
catch
{
 // code to handle the exception
 info("I would like to inform you that an error occurred"); 
}




try
{
 // code that might throw an exception
}
catch (Exception::Error)
{
 // code to handle the exception
 error("An error occurred: %1", Exception::getMessage());
}

2. The throw statement: You can use the throw statement to throw an exception from your code. This can be useful for signaling that an error has occurred and for providing additional information about the error.

if (someCondition)
{
 throw error("An error occurred because someCondition is true");
}

3. The Error class: You can use the Error class to create and throw an exception. The Error class provides several constructors for creating an exception with a specific error message or with additional information about the error.

if (someCondition)
{
 Error e = new Error("An error occurred because someCondition is true");
 e.addInfo(infoNum(someVariable));
 throw e;
}

4. Logging: You can use the error(), warning() and info() methods provided by the SysOperation framework, or the EventLog class to log errors and exceptions. This can be useful for tracking and troubleshooting issues that arise in your application.

try
{
 // code that might throw an exception
}
catch (Exception::Error)
{
 error("An error occurred: %1", Exception::getMessage());
 EventLog::error("An error occurred: %1", Exception::getMessage());
} 

It's important to properly handle errors and exceptions in your X++ code, to ensure that your application is robust and reliable, and to make it easier to troubleshoot and fix any issues that may arise.

You can also have below

try
{
  // Code here.
}
catch (Exception::Numeric)
{
  info("Caught a Numeric exception.");
}
catch
{
  info("Caught an exception.");
}
finally
{
  // Executed no matter how the try block exits.
}

Sample code

// Method to demonstrate exception handling
static void ExceptionHandling(Args _args)
{
    try
    {
        // Execute some code
        info("Now I'm here 1");
        
        // Simulate an error condition
        if (true)
        {
            throw error("Oops! Something happened");
        }

        info("Now I'm there 2");
    }
    catch (Exception::Error)
    {
        // Handle general error exception
        info("I would like to inform you that an error occurred");
    }
    catch (Exception::Deadlock)
    {
        // Handle deadlock exception
        // Wait for 10 seconds and retry
        sleep(10000);
        retry;
    }
    
    // End of the method
    info("This is the end");
}

Types of error and exceptions

You can throw several error exceptions:

• Break - The user pressed Break or Ctrl + C.
• CLRError - The error occurred while the CLR functionality was being used.
• CodeAccessSecurity - An error occurred while the CodeAccessPermission.demand method was being used.
• DDEerror - An error occurred while the DDE system class was being used.
• Deadlock - A database deadlock occurred because several transactions are waiting for each other.
• DuplicateKeyException - An error occurred in a transaction that is using Optimistic Concurrency Control. The transaction can be retried.
• DuplicateKeyExceptionNotRecovered - An error occurred in a transaction that is using Optimistic Concurrency Control. The code won't be retried, and this exception cannot be caught in a transaction.
• Error - A fatal error occurred. The transaction has been stopped.
• Internal - An internal error occurred in the development system.
• Numeric - An error occurred when the str2int, str2int64, or str2num function was used.
• UpdateConflict - An error occurred in a transaction during an update.
• UpdateConflictNotRecovered - An error occurred in a transaction during an update. This exception cannot be retried.
• TransientSQLConnectionError - An error occurred during the query run. The transaction will be canceled. This exception will not be caught within a transaction.