javawebparts.filter
Class JSCompressionFilter

java.lang.Object
  |
  +--javawebparts.filter.JSCompressionFilter

All Implemented Interfaces:

javax.servlet.Filter

public class JSCompressionFilter

extends java.lang.Object

implements javax.servlet.Filter

This filter does some simple javascript compressing in the response. It uses a slightly modified version of JSMin.java from John Reilly which, in it's turn, is a java version of Douglas Crockford's jsmin.c. If you want to know how it works and what is does: www.crockford.com It allows for including or excluding paths from filter functionality.

Init parameters are:

• pathSpec - Either "include" or "exclude". This determines whether the list of paths in the pathList parameter is a list of paths to include in filter functionality, or a list of paths to exclude. Required: No. Default: None.



• pathList - This is a comma-separated list of paths, which can use asterisk for wildcard support, that denotes either paths to include or exclude from the functioning of this filter (depending on what pathSpec is set to). The paths ARE case-senitive! There is no limit to how many items can be specified, although for performance reasons a developer will probably want to specify as few as possible to get the job done (each requested path is matched via regex). Note also that you are of course still required to specify a path for the filter itself as per the servlet spec. This parameter however, together with pathSpec, gives you more control and flexibility than that setting alone. Required: No. Default: None.
  
  General note on pathSpec and pathList: If pathSpec is not specified but pathList IS, then 'exclude' is assumed for pathSpec. If pathSpec is specified by pathList IS NOT, then the filter WILL NEVER EXECUTE (this is technically a misconfiguration). If NEITHER is defined then the generic filter mapping will be in effect only.

Example configuration in web.xml:

<filter>
<filter-name>JSCompressionFilter</filter-name>
<filter-class>javawebparts.filter. JSCompressionFilter</filter-class>
<init-param>
<param-name>pathSpec</param-name>
<param-value>include</param-value>
</init-param>
<init-param>
<param-name>pathList</param-name>
<param-value>*‍/smalljavascript.js</ param-value>
</init-param>
</filter>

<filter-mapping>
<filter-name>JSCompressionFilter</filter-name>
<url-pattern>/*.js</url-pattern>
</filter-mapping>

Author:

Herman van Rosmalen .

Field Summary

private static org.apache.commons.logging.Log	log Log instance.
private static java.util.ArrayList	pathList List of paths for filter functionality determination.
private static java.lang.String	pathSpec Whether pathList includes or excludes.

Constructor Summary

JSCompressionFilter()

Method Summary

private byte[]	compress(byte[] bytes, boolean isHtml) Do compression.
void	destroy() Destroy.
void	doFilter(javax.servlet.ServletRequest request, javax.servlet.ServletResponse response, javax.servlet.FilterChain filterChain) Do filter's work.
void	init(javax.servlet.FilterConfig filterConfig) Initialize this filter.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

log

private static org.apache.commons.logging.Log log

Log instance.

pathSpec

private static java.lang.String pathSpec

Whether pathList includes or excludes.

pathList

private static java.util.ArrayList pathList

List of paths for filter functionality determination.

Constructor Detail

JSCompressionFilter

public JSCompressionFilter()

Method Detail

destroy

public void destroy()

Destroy.

Specified by:

destroy in interface javax.servlet.Filter

init

public void init(javax.servlet.FilterConfig filterConfig)
          throws javax.servlet.ServletException

Initialize this filter.

Specified by:

init in interface javax.servlet.Filter

Parameters:

filterConfig - The configuration information for this filter.

Throws:

javax.servlet.ServletException - ServletException.

doFilter

public void doFilter(javax.servlet.ServletRequest request,
                     javax.servlet.ServletResponse response,
                     javax.servlet.FilterChain filterChain)
              throws javax.servlet.ServletException,
                     java.io.IOException

Do filter's work.

Specified by:

doFilter in interface javax.servlet.Filter

Parameters:

request - The current request object.

response - The current response object.

filterChain - The current filter chain.

Throws:

javax.servlet.ServletException - ServletException.

java.io.IOException - IOException.

compress

private byte[] compress(byte[] bytes,
                        boolean isHtml)

Do compression.

Parameters:

bytes - The text to check

isHtml - Are we compressing Html (or a .js file)

Returns:

byte[] The compressed result