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Rewrite 1.1.0.Final introduces the OutputBuffer – What Servlet always wanted but could never have

Posted by: Lincoln Baxter III on 07/25/2012

Output buffering is a feature often desired but rarely properly implemented – Properly resetting the Response stream, preserving headers correctly, writing to disk so you don’t overflow the JVM memory space – in Rewrite, we hope to make this attainable for anyone seeking to do things like:

Dynamic minification of HTML, JavaScript, and/or CSS files
Modification of output HTML or content before it is sent to the client.
Reduction of build and development complexity by transforming LESS or SASS files into CSS on the Server
Got more ideas?… tell us.?

Now, using the Rewrite’s “OutputBuffer” API introduced in the new version 1.1.0.Final, you can finally achieve this in just a few lines of code, either by wrapping a stream, or simply modifying the contents directly!Want to make every first word in your application bold or remove all punctuation? You probably won’t make too many friends, but you could do it if you wanted to. Maybe we should start by changing all links in the app to this educational video. Or maybe we’ll just make everything lowercase:

Create an OutputBuffer

import java.io.ByteArrayInputStream;
import java.io.InputStream;
import org.ocpsoft.common.util.Streams;

public class OutputToLowercase implements OutputBuffer
{
   @Override
   public InputStream execute(InputStream input)
   {
      String contents = Streams.toString(input);
      return new ByteArrayInputStream(contents.toLowerCase().getBytes());
   }
}

Use it in your ConfigurationProviderSource

public Configuration getConfiguration(final ServletContext context)
   {
      return ConfigurationBuilder.begin()
               .addRule()
               .when(Path.matches("/index.html"))
               .perform(Response.withOutputBufferedBy(new OutputToLowercase()));
   }

Combine that with a little bit of Rewrite-style configuration, and you’ve got a simple recipe for output modification. Some of the features to come in Rewrite 2.0, including a simplified output Transform API, are based on this technology. So if you want to get a head start, you can try a 2.0.0-SNAPSHOT, or just wait a few weeks

Get Rewrite version 1.1.0.Final, or see everything that’s new.

VERSION 1.1.0

Features & Enhancements:

Enabled fluent chaining of additional Condition and Operation instances when adding single/custom rules by calling ConfigurationBuilder.addRule(new CustomRule()).when(...).perform(...);
Added Response output buffering support
JAAS support with JAASRoles condition
Content Delivery Network support with CDN rule
Typesafe method invocation support
Issue #30 – Tasks may now be performed in a SubFlow without affecting the Flow of the entire Rewrite event.
Preview of Transformer APIs
Preview of Annotation Configuration API

Regression Impact:

Configuration strings are now literal. Regular expressions must be configured through a parameter such as: .defineRule().when(Path.matches("/{*}").where("*").matches(".*"))
Join no longer matches Forwarded requests.
EL API is now a separate module and the Java package name has changed to ‘org.ocpsoft.rewrite.el’

Bug Fixes:

Parameter binding now works on Join rules.
Issue #67 – Keep order of fluent rules when building configuration.
Fixed NumberFormatException on EncodeQuery operation when hashCode of checksum is modified
Fixed ArrayIndexOutOfBounds exception for parsing query-strings with a separator but no content “?”
Fixed showcase applications
Issue #51 – Join no longer matches its own Forwarded requests.
Fixed GWT integration issue where context path was not correctly transmitted when client application is hosted under the root URL “/”
TypeBasedExpression no longer requires the expression to be surrounded by “#{…}”
Fixed bug where container would swallow certain resource requests, resulting in false 404 errors
Issue #32 – PhaseBinding defers validation and conversion until within the JSF lifecycle.
Issue #33 – ClassVisitorImpl now supports adding rules to the ConfigurationBuilder if necessary
Fixed some bugs with URLEncoding/URLDecoding

Lincoln Baxter III's complete blog can be found at: http://ocpsoft.com

About Lincoln Baxter III

Creator of PrettyFaces - Url Rewriting for JSF, PrettyTime - Social-style date & time formatting for Java, and a community contributor to the JSF2 Expert Group; his latest project is ScrumShark, an open-source agile project management tool.

Beginning his career in C, C++ development for hardware signal testing automation, Lincoln soon moved on to Perl, dynamic programming languages, artificial intelligence and, more recently - web application frameworks such as Java Server Faces and Groovy on Grails for financial and small business solutions.

When he is not swimming, running, or playing Ultimate Frisbee, Lincoln is focused on improving the openness of Java, the Java Community Process(JCP), and bringing the J2EE platform to small businesses and freelancers.

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