Creating a simple static file server with Rewrite

Today, I’d like to take a quick moment to demonstrate how to make a simple file server using [[Rewrite]], and any Servlet Container, such as Tomcat, Wildfly, or Jetty. This can enable much easier file updates for static content, such as preventing the need to re-deploy an entire application just to update an image, or document.

[[Rewrite]] is an open-source Routing ↑↓ and /url/{rewriting} solution for Servlet, Java Web Frameworks, and Java EE.

To start, you’ll need to include the Rewrite dependencies in your project. If you’re using maven, this is as simple as making sure your POM has the following entries (You’ll also need the Servlet API):

Include Rewrite in your 'pom.xml'

<dependency>
   <groupId>org.ocpsoft.rewrite</groupId>
   <artifactId>rewrite-servlet</artifactId>
   <version>2.0.8.Final</version>
</dependency>
<dependency>
   <groupId>javax.servlet</groupId>
   <artifactId>javax.servlet-api</artifactId>
   <version>3.1.0</version>
   <scope>provided</scope>
</dependency>

Next, we’ll create a simple ConfigurationProvider to tell Rewrite what to do; in this case, we’ll be streaming files directly from the local filesystem. This class can go anywhere in your project:

The Rewrite ConfigurationProvider

@RewriteConfiguration
public class StaticContentConfiguration extends HttpConfigurationProvider {
   @Override
   public Configuration getConfiguration(ServletContext context) {
      /*
       * You should select a path that exposes only the directory(s) from which content should be served, otherwise the
       * entire hard drive could be accessible.
       */
      File resource = new File("/home/contentserv/{file}");

      return ConfigurationBuilder.begin()
               .addRule()
               .when(Path.matches("/{file}")
                        .and(Filesystem.fileExists(resource))
                        .and(Direction.isInbound())
               )
               .perform(Stream.from(resource)
                        .and(Response.setStatus(200))
                        .and(Response.complete())
               )
               .where("file").matches(".*");
   }

   @Override
   public int priority() {
      return 0;
   }
}

You could even add logging using the provided `Log` operation from rewrite-servlet, so that requests can be tracked in your server logs:

.perform(Stream.from(resource)
   .and(Response.setStatus(200))
   .and(Response.complete())
   .and(Log.message(Level.INFO, "Served file: {file}."))
)

It’s as simple as that! Rewrite will match inbound requests with corresponding files in the specified resource location. Thanks to the simple parameterization API that Rewrite provides, this requires very little glue code – we are free to sit back and have a nice beverage.

Now you’ve not got an extremely simple file-server running as a web-application. This is only one very basic example of what Rewrite can do, so let us know what you think as you explore more Rewrite features or dive into the documentation!

Posted in Servlet

return ConfigurationBuilder.begin() .addRule() .when(Path.matches("/{file}") .and(Filesystem.fileExists(resource)) .and(Direction.isInbound()) ) .perform(Stream.from(resource) .and(Response.setStatus(200)) .and(Response.complete()) ) .where("file").constrainedBy(new Constraint() { public boolean isSatisfied(Rewrite event, EvaluationContext context, String value) { return !value.contains("../") } });