Resolving the ?upper_case Issue in Advanced PDF Templates

Advanced PDF templates often rely on FreeMarker expressions to dynamically format and display data. One common challenge developers face is ensuring that address fields or other dynamic content are properly transformed to uppercase while preserving special characters and XML compatibility. This article explores the issue with the ?upper_case directive and presents a robust solution

The Problem: ?upper_case Misbehaving

When using FreeMarker’s ?upper_case directive on a string like shipAddress, unexpected behavior can occur if the string contains special characters such as:

• & (ampersand)
• < and > (angle brackets)
• ' (single quote)
• " (double quote)

These characters can interfere with XML rendering or cause encoding issues in the final PDF output. Additionally, applying ?upper_case directly may not preserve the intended formatting or escape sequences.

The Solution: Preprocessing Before Uppercasing

To address this, the string must be sanitized and escaped before applying ?upper_case. Here’s the recommended FreeMarker expression:

${shipAddress?string

  ?replace(“(?i)&”,”&”,”r”)

  ?replace(“(?i)<“,”<“,”r”)

  ?replace(“(?i)>”,”>”,”r”)

  ?replace(“(?i)'”,”‘”,”r”)

  ?replace(“(?i)””,”””,”r”)

  ?upper_case?xml}

Breakdown of the Expression

• ?string: Ensures the input is treated as a string.
• ?replace("(?i)..."): Uses case-insensitive regex to replace special characters with their literal equivalents.
• ?upper_case: Converts the sanitized string to uppercase.
• ?xml: Escapes the final output for XML compatibility.

Why This Works

By preprocessing the string:

• You avoid double-escaping or malformed XML.
• You ensure that ?upper_case doesn’t interfere with special character encoding.
• You maintain clean, readable output in the final PDF.

Best Practices

• Always sanitize user-generated content before applying transformations.
• Use ?xml at the end to ensure safe rendering in XML-based templates.
• Test with edge cases like names containing symbols or HTML entities.

Final Thoughts

This approach ensures that your PDF templates remain robust, readable, and free from encoding errors. It’s a small tweak with a big impact—especially when dealing with international addresses or complex data inputs.

If you’d like, I can help you turn this into a documentation snippet or integrate it into your template guide.

Why This Works

By preprocessing the string:

• You avoid double-escaping or malformed XML.
• You ensure that ?upper_case doesn’t interfere with special character encoding.
• You maintain clean, readable output in the final PDF.

Best Practices

• Always sanitize user-generated content before applying transformations.
• Use ?xml at the end to ensure safe rendering in XML-based templates.
• Test with edge cases like names containing symbols or HTML entities.

Final Thoughts

This approach ensures that your PDF templates remain robust, readable, and free from encoding errors. It’s a small tweak with a big impact—especially when dealing with international addresses or complex data inputs.

If you’d like, I can help you turn this into a documentation snippet or integrate it into your template guide.

Best Practices

• Always sanitize user-generated content before applying transformations.
• Use ?xml at the end to ensure safe rendering in XML-based templates.
• Test with edge cases like names containing symbols or HTML entities.

Final Thoughts

This approach ensures that your PDF templates remain robust, readable, and free from encoding errors. It’s a small tweak with a big impact—especially when dealing with international addresses or complex data inputs.