RewritePath transform

This topic tells you about the Application Accelerator RewritePath transform in Tanzu Application Platform (commonly known as TAP).

The RewritePath transform allows you to change the name and path of files without affecting their content.

Syntax reference

RewritePath(regex: REGEX, rewriteTo: SPEL-EXPRESSION, matchOrFail:BOOLEAN)

Where:

REGEX is a regular expression (regex). For each input file, RewritePath attempts to match its path by using this regex. If the regex matches, RewritePath changes the path of the file to the evaluation result of rewriteTo.
SPEL-EXPRESSION is a SpEL expression that has access to the overall engine model and to variables defined by capturing groups of the regular expression. Both named capturing groups (?<example>[a-z]*) and regular index-based capturing groups are supported. g0 contains the whole match, g1 contains the first capturing group, and so on.
BOOLEAN is the behavior you want if the regex doesn’t match:
- If set to false, which is the default, the file is left untouched.
- If set to true, an error occurs. This prevents misconfiguration if you expect all files coming in to match the regex. For more information about typical interactions between RewritePath and Chain + Include, see the following section, Interaction with Chain and Include.

Default values

The default values for RewritePath are as follows:

regex: The default is the following regular expression, which provides convenient access to some named capturing groups:
```
^(?<folder>.*/)?(?<filename>([^/]+?|)(?=(?<ext>\.[^/.]*)?)$)
```
Using some/deep/nested/file.xml as an example, the default regular expression captures:
- folder: The full folder path the file is in. In this example, some/deep/nested/.
- filename: The full name of the file, including extension if present. In this example, file.xml.
- ext: The last dot and extension in the filename, if present. In this example, .xml.
rewriteTo: The default is the expression #folder + #filename, which doesn’t rewrite paths.
matchOrFail: The default is false, which leaves the file untouched if the regex doesn’t match.

Examples

See the following examples using the RewritePath transform.

Example 1

The following moves all files from src/main/java to sub-module/src/main/java:

RewritePath(regex: "src/main/java/(.*)", rewriteTo: "sub-module/src/main/java" + #g1)

Diagram showing a RewritePath transform.

Example 2

The following flattens all files found inside the sub-path directory and its subdirectories, and puts them into the flattened folder:

RewritePath(regex: "sub-path/(.*/)*(?<filename>[^/]+)", rewriteTo: "flattened" + #filename)

Example 3

The following turns all paths into lowercase:

RewritePath(rewriteTo: #g0.toLowerCase())

Interaction with Chain and Include

It’s common to define pipelines that perform a Chain of transformations on a subset of files, typically selected by Include/Exclude:

Include({"**/*.java"})
T1()
T2()
T3()

If one of the transformations in the chain is a RewritePath operation, chances are you want the rewrite to apply to all files matched by the Include. For those typical configurations, you can set the matchOrFail guard to true to ensure the regex you provide indeed matches all files coming in.