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Troubleshooting

This page provides solutions for common issues you might encounter when using OfficeStamper.

Common Errors and Solutions

Expression Evaluation Errors

Symptoms

  • Exception with a message like "Failed to evaluate expression: ${…​}"
  • Placeholders remain unchanged in the output document
  • OfficeStamperException with details about the expression that failed

Possible Causes and Solutions

Cause Solution
Syntax error in expression Check the expression syntax. Make sure all brackets, quotes, and operators are placed correctly.
Missing property in context object Ensure the property exists in your context object and is accessible (has a getter method or is public).
Null value in a property chain Use the safe navigation operator (?.) to handle potential null values in property chains, for example ${person?.address?.city}.
Type mismatch Ensure the types in your expressions match the expected types. For example, don’t try to call string methods on numbers.

Customizing Error Handling

You can customize how Office-stamper handles expression evaluation errors:

// Default behavior: throw an exception
var configuration = OfficeStamperConfigurations.standardWithPreprocessing()
    .setExceptionResolver(ExceptionResolvers.throwing());

// Alternative: leave placeholders unchanged and log the error
var configuration = OfficeStamperConfigurations.standardWithPreprocessing()
    .setExceptionResolver(ExceptionResolvers.passing());

// Alternative: replace failed expressions with a default value
var configuration = OfficeStamperConfigurations.standardWithPreprocessing()
    .setExceptionResolver(ExceptionResolvers.defaulting("ERROR"));

Comment Processing Errors

Symptoms

  • Exception with a message like "Failed to process comment: …​"
  • Comments remain in the output document
  • Unexpected document structure

Possible Causes and Solutions

Cause Solution
Invalid comment syntax Ensure the comment follows the expected format for the processor you’re using.
Missing or invalid parameters Check the parameters passed to the comment processor are of the correct type and exist in your context.
Collection is null or empty When using repeatXXX processors, ensure the collection is not null and contains elements.
Condition evaluates to null When using displayXXXIf processors, ensure the condition evaluates to a boolean, not null.

Formatting Issues

Symptoms

  • Text appears with unexpected formatting
  • Images are too large or too small
  • Tables have incorrect structure

Possible Causes and Solutions

Cause Solution
Complex formatting in template Simplify the formatting in your template. Use basic styles and avoid complex nested formatting.
Image size isn’t specified Set the width and height of images using the Image class methods.
Table structure mismatch When using resolveTable, ensure your StampTable structure matches the expected format.
Line breaks not working Ensure you’re using the correct line break placeholder (default is \n).

Performance Issues

Symptoms

  • Slow processing of documents
  • High memory usage
  • OutOfMemoryError

Possible Causes and Solutions

Cause Solution
Large documents Process documents in smaller chunks if possible.
Many repeated sections Limit repetitions or split the document into multiple smaller documents.
Complex expressions Simplify expressions and avoid unnecessary calculations.
Memory leaks Ensure you’re closing all resources using try-with-resources.

Debugging Techniques

Logging

Office-stamper uses SLF4J for logging. You can configure your logging framework to see more detailed information about what’s happening during the stamping process.

Example with Logback:

<logger name="pro.verron.officestamper" level="DEBUG" />

Inspecting the Template

Sometimes issues arise from the template itself. You can:

  1. Open the .docx file in Word
  2. Check for hidden text or fields that might interfere with expressions.
  3. Verify that comments are correctly attached to the intended paragraphs or elements.
  4. Simplify complex formatting

Examining the Context Object

Make sure your context object contains all the expected properties, and they have the correct values:

// Before stamping, log the context object
System.out.println("Context: " + context);

// Or create a simple test to verify properties
assert context.getPerson().getName() != null : "Person name is null";

Creating a Minimal Reproduction

If you’re having trouble identifying the issue, try creating a minimal reproduction:

  1. Start with a plain template and context
  2. Add element one by one until the issue appears
  3. This helps isolate exactly what’s causing the problem

Getting Help

If you’re still having issues after trying the solutions above:

  1. Check the GitHub Issues to see if someone else has reported the same problem.
  2. Create a new issue with:
    • A minimal reproduction of the problem
    • Your template document (if possible)
    • The code you’re using to stamp the document
    • The full stack trace of any exceptions
    • Expected versus actual output

Next Steps