javawebparts.filter
Class CompressionFilter

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

All Implemented Interfaces:

javax.servlet.Filter

public class CompressionFilter

extends java.lang.Object

implements javax.servlet.Filter

This filter allows for compressing the response from the server. It allows for including or excluding paths from filter functionality. It also allows for defining what type of compression should be used, if supported by the client, and in what order.

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.



• compressType - What type of compression to perform. The valid values are 'gzip_only' (GZip will be used, if supported), 'deflate_only' (Deflate will be used, if supported), 'gzip_first' (GZip will be used if supported, otherwise Deflate will be used, if supported), 'deflate_first' (Deflate will be used if supported, otherwise GZip will be used if supported). Required: Yes. Default: None (must be one of the valid values).

Example configuration in web.xml:

<filter>
<filter-name>CompressionFilter</filter-name>
<filter-class>javawebparts.filter. CompressionFilter</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>*‍/bigimage2.gif</ param-value>
</init-param>
<init-param>
<param-name>compressType</param-name>
<param-value>gzip_first</param-value>
</init-param>
</filter>

<filter-mapping>
<filter-name>CompressionFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

Author:

Frank W. Zammetti.

Field Summary

private java.lang.String	compressType What type of oompression we want this filter to do.
private static org.apache.commons.logging.Log	log Log instance.
private java.util.ArrayList	pathList List of paths for filter functionality determination.
private java.lang.String	pathSpec Whether pathList includes or excludes.

Constructor Summary

CompressionFilter()

Method Summary

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 java.lang.String pathSpec

Whether pathList includes or excludes.

pathList

private java.util.ArrayList pathList

List of paths for filter functionality determination.

compressType

private java.lang.String compressType

What type of oompression we want this filter to do. Valid values are "gzip_only", "deflate_only", "gzip_first" and "deflate_first". If neither compression type is supported by the client, no compression is attempted. If the client supports both and this option is "gzip_first", GZip be used if it is supported, or Deflate if not, and the exact opposite is true when "deflate_first" is used. If set to "gzip_first" but only Deflate is supported, Deflate will be used, and vice-versa.

Constructor Detail

CompressionFilter

public CompressionFilter()

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.