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Discover how to properly escape the dot character in `Apache Velocity` templates to effectively access variable properties.
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This video is based on the question https://stackoverflow.com/q/74777743/ asked by the user 'hakuna matata' ( https://stackoverflow.com/u/1001335/ ) and on the answer https://stackoverflow.com/a/74777966/ provided by the user 'Vini' ( https://stackoverflow.com/u/98044/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Mastering Apache Velocity Templating: Escaping the Dot Character

When working with templates in Apache Velocity, you might encounter some unexpected behavior when trying to access properties of variables. One common challenge developers face is how to handle the dot (.) character when attempting to reference properties of a variable. In this guide, we will explore this issue and provide you with a clear solution to ensure your templates function as intended.

The Problem: Accessing Variable Properties

Imagine you have a template where you're trying to reference constants of a class through a variable. Here’s an example of what that might look like:

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In this example, $class_name is a variable provided in the VelocityContext:

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You might expect that this would yield the following output:

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However, the output makes it clear that there was no substitution:

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The attempt to escape the dot (.) using a backslash, like this:

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Results in unwanted output where the backslash is additionally printed:

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The Misunderstanding of Escaping

You might be wondering why the dot character behaves this way in Apache Velocity. Escaping in many programming languages is commonly done using a backslash, but in Velocity, this is not the correct approach for accessing variable properties. Instead, there’s a better and simpler method.

The Solution: Using Curly Braces

To resolve this issue, you can use curly braces around the variable name. This is how you can achieve the expected outcome efficiently. Here’s how to adjust your template:

Updated Template

Instead of using the variable directly, encapsulate it with curly braces:

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Expected Output

With this adjustment, running your code will now produce the desired output:

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Conclusion

Handling variable properties in Apache Velocity can initially seem tricky, especially with the behavior of the dot character. However, by simply wrapping your variable in curly braces, you can easily access the properties associated with it without any unwanted escape characters. This approach is straightforward and will save you time while working on your templates.

Now you can confidently tackle issues related to escaping the dot character in your Apache Velocity projects. Happy templating!