To Infinity and Beyond …

package com.vinu.web.performance;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.StringReader;
import java.io.StringWriter;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;

import org.mozilla.javascript.ErrorReporter;
import org.mozilla.javascript.EvaluatorException;

import com.yahoo.platform.yui.compressor.CssCompressor;
import com.yahoo.platform.yui.compressor.JavaScriptCompressor;

/**
* @author Vinu Varghese (Email: vinu@x-minds.org) Minifies JS and CSS on the fly, based on the YUI Compressor The minification is a heavy process so use this
* filter along with a caching filter for performance.
*/
public class JsCssMinifyFilter implements Filter
{

private FilterConfig config;

/*
* (non-Javadoc)
*
* @see javax.servlet.Filter#init(javax.servlet.FilterConfig)
*/
public void init(FilterConfig filterConfig) throws ServletException
{
this.config = filterConfig;
}

/*
* (non-Javadoc)
*
* @see javax.servlet.Filter#doFilter(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain)
*/
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException
{
HttpServletRequest originalRequest = (HttpServletRequest) request;

HttpServletResponse originalResponse = (HttpServletResponse) response;

// Create the response wrapper
MinifiedResponse minifiedResponse = new MinifiedResponse(originalResponse);

// Continue the chain - get the contents
chain.doFilter(originalRequest, minifiedResponse);

// The data
String data = new String(minifiedResponse.getData());

// Create the reader
StringReader reader = new StringReader(data);
//Create the writer
StringWriter writer = new StringWriter();

String requestURI = originalRequest.getRequestURI();

try
{
//Do JS minification
if (requestURI.endsWith(".js"))
{
minifyJS(reader, writer);
}
// Do Css minification
else if (requestURI.endsWith(".css"))
{
minifyCSS(reader, writer);
}
//Else - we can't do any other minification
else
{
writer.write(data);

}

}
catch (Exception ex)
{
// We do a generic exception handling

//Log error
config.getServletContext().log("Error in minifying : " + requestURI, ex);
// Write the data as it is
writer.write(data);
}

//Write the data to the original response

// Get the data from the writer (Compressed data)
String compressed = writer.toString();

//Set the content length correctly
originalResponse.setContentLength(compressed.length());

//Write the data
originalResponse.getOutputStream().write(compressed.getBytes());

}

/**
* @param reader
* @param writer
* @throws IOException
*/
private void minifyCSS(StringReader reader, StringWriter writer) throws IOException
{
CssCompressor cssCompressor = new CssCompressor(reader);
cssCompressor.compress(writer, -1);
}

/**
* @param reader
* @param writer
*/
private void minifyJS(StringReader reader, StringWriter writer) throws IOException
{
JavaScriptCompressor compressor = new JavaScriptCompressor(reader, new ErrorReporter() {

public void warning(String message, String sourceName, int line, String lineSource, int lineOffset)
{
if (line < 0)
{
System.err.println("\n[WARNING] " + message);
}
else
{
System.err.println("\n[WARNING] " + line + ':' + lineOffset + ':' + message);
}
}

public void error(String message, String sourceName, int line, String lineSource, int lineOffset)
{
if (line < 0)
{
System.err.println("\n[ERROR] " + message);
}
else
{
System.err.println("\n[ERROR] " + line + ':' + lineOffset + ':' + message);
}
}

public EvaluatorException runtimeError(String message, String sourceName, int line, String lineSource, int lineOffset)
{
error(message, sourceName, line, lineSource, lineOffset);
return new EvaluatorException(message);
}
});

// Does the compression
compressor.compress(writer, -1, true, false, true, false);

}

/*
* (non-Javadoc)
*
* @see javax.servlet.Filter#destroy()
*/
public void destroy()
{

}

/**
* A response wrapper, the content is saved to the output buffer, the stream returned is ServletOutputStreamWrapper
*
* @author Vinu Varghese (Email: vinu@x-minds.org)
*
*/
class MinifiedResponse extends HttpServletResponseWrapper
{

private ByteArrayOutputStream output = new ByteArrayOutputStream();

/**
* @param response
*/
public MinifiedResponse(HttpServletResponse response)
{
super(response);
}

/*
* (non-Javadoc)
*
* @see javax.servlet.ServletResponseWrapper#getOutputStream()
*/
@Override
public ServletOutputStream getOutputStream() throws IOException
{
return new ServletOutputStreamWrapper(this.output);
}

/*
* (non-Javadoc)
*
* @see javax.servlet.ServletResponseWrapper#getWriter()
*/
@Override
public PrintWriter getWriter() throws IOException
{
PrintWriter localPrintWriter;
try
{
localPrintWriter = new PrintWriter(new OutputStreamWriter(getOutputStream(), "UTF-8"), true);
}
catch (Exception localException)
{
localPrintWriter = new PrintWriter(getOutputStream(), true);
}

return localPrintWriter;
}

/**
* Returns the data
*
* @return
*/
public byte[] getData()
{
try
{
output.flush();
}
catch (IOException e)
{
//ignore
}

return output.toByteArray();
}

}

/**
* Output stream wrapper I have overriden the write method, is that enough?
*
* @author Vinu Varghese (Email: vinu@x-minds.org)
*
*/
class ServletOutputStreamWrapper extends ServletOutputStream
{

private ByteArrayOutputStream output;

/**
*
*/
public ServletOutputStreamWrapper(ByteArrayOutputStream output)
{
this.output = output;
}

/*
* (non-Javadoc)
*
* @see java.io.OutputStream#write(int)
*/
public void write(int b) throws IOException
{
output.write(b);
}

}