Apache Sling File Optimization
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Apache Sling File Optimization

Bundle for optimizing files stored in the Apache Sling repository. Includes a plugin architecture for providing file optimizers and hooks to automatically and manually optimize files.

The file optimizer includes the ability to revert the optimized file either using the Sling Post Operation or via the API. Resources can be excluded from optimization by setting the optim:disabled attribute to true.

This module is part of the Apache Sling project.

Using the File Optimization Library

There are four different methods for interacting with the File Optimizer: using the Event Handler, interacting with the Servlets / Post Operations, using the Filter or invoking the API directly.

Event Handler

The File Optimizer Event Handler can be used to automatically optimize file resources when Sling Events occur. The File Optimizer Event Handler is not enabled by default, to enable it, you will need to enable the Event Handler with an OSGi Config like:

# Example Event Filter
event.filter=(&(resourceType=sling:File)(|(path=*.png)(path=*.jpg)))
# Example Event Topic
event.topic=org/apache/sling/api/resource/Resource/CHANGED

Servlet / Post Operations

There are four servlets / Sling Post Servlet operations for interacting with the File Optimization API.

OptimizeFileOperation

This operation will optimize a File resource. Example usage:

curl -d ":operation=fileoptim:optimize" -X POST http://localhost:8080/content/afile.jpg

RestoreOriginalOperation

This operation will restore the original contents of an optimized File resource. Example usage:

curl -d ":operation=fileoptim:restore" -X POST http://localhost:8080/content/afile.jpg

FileOptimizerData

This servlet will return the JSON data for the results of an optimization operation if it were run against the specified resource. Example usage:

curl http://localhost:8080/system/fileoptim.json?path=/content/afile.jpg

Example response:

{
    "algorithm": "Apache Sling JPEG File Optimizer",
    "originalSize": 1000,
    "optimizedSize", 500,
    "optimized", false,
    "preview", "/system/fileoptim/preview?path=/content/afile.jpg",
    "savings", 0.5
}

FileOptimizerPreview

This servlet will return the optimized binary as if the File Optimizer were run against the specified resource. Example usage:

curl http://localhost:8080/system/fileoptim/preview?path=/content/afile.jpg

Filter

The File Optimizer Filter can be used to automatically optimize file resources when serving the content. The File Optimizer Filter is not enabled by default, to enable it, you will need to enable the Filter with an OSGi Config like:

# Example Filter Scope
sling.filter.scope=REQUEST

API

The File Optimizer service can be retrieved by reference, for example:

@Reference
private FileOptimizerService fileOptimSvc;

public void optimizeFile(Resource fileResource) {
    fileOptimSvc.optimizeFile(fileResource, true);
}

Additionally, there are two Sling mdoels for discovering the optimization information of resources.

  • org.apache.sling.fileoptim.models.OptimizedFile - Allows for retrieval of the data from a file which has been optimized
  • org.apache.sling.fileoptim.models.OptimizeResource - Allows for determining if a resource can be optimized and what the results would be if it were

Defining a File Optimizer

File optimizers are used by the library to optimize resources based on the file mime type. Each File Optimizer should implement the FileOptimizer interface, setting the mime.type property to the MimeTypes for which the optimizer is applicable. The Service Rankin property can be used to override the default File Optimizers.

@Component(service = FileOptimizer.class, property = { FileOptimizer.MIME_TYPE + "=image/jpeg" })
public class DevNullFileOptimizer implements FileOptimizer {

    private static final Logger log = LoggerFactory.getLogger(DevNullFileOptimizer.class);

    @Override
    public byte[] optimizeFile(byte[] original, String metaType) {
        // TODO: Actually do something with the file contents here and return the optimized file
        return new byte[0];
    }

    @Override
    public String getName() {
        return "/dev/null File Optimizer";
    }
}