Module com.aoapps.servlet.lastmodified

Package com.aoapps.servlet.lastmodified

Class LastModifiedServlet

java.lang.Object

javax.servlet.GenericServlet

javax.servlet.http.HttpServlet

com.aoapps.servlet.lastmodified.LastModifiedServlet

All Implemented Interfaces:

Serializable, Servlet, ServletConfig

public class LastModifiedServlet
extends HttpServlet

Sets the modified time to that of the file itself and all dependencies. Currently only *.css supported.

When mapped to handle *.css files, parses the underlying file from the web resources and automatically adds lastModified=#### URL parameters. This allows the replacement of files to be immediately visible to browsers while still efficiently caching when nothing changed.

The current CSS parser is extremely simple and may not catch all URLs. Specifically, it only looks for URLs on a line-by-line basis and does not support backslash (\) escapes. (TODO: Are backslash escapes even part of CSS?)

TODO: Handle escapes, which might require a parser more complicated than this regular expression, including escaped quotes in quotes, or escaped parenthesis: https://developer.mozilla.org/en-US/docs/Web/CSS/url(), https://stackoverflow.com/questions/25613552/how-should-i-escape-image-urls-for-css.

All files must be in the StandardCharsets.UTF_8 encoding.

TODO: Add support for non-url imports TODO: Review recursive import url(...) works correctly (urls within the included urls should be applied)

TODO: Rewrite all URLs to be app-relative, with contextPath prefixed, much like how other URLs are rewritten. This is so paths will still be relative to the CSS file even when included into a page directly.

See Also:

• This requires the cache be active
• Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	LastModifiedServlet.ParsedCssFileCache	Creates the LastModifiedServlet.ParsedCssFile cache during application start-up.

Field Summary

Fields

Modifier and Type	Field	Description
static final String	DEFAULT_CACHE_CONTROL	The default, short-term, cache-control header value.
static final String	LAST_MODIFIED_HEADER_NAME	The header that may be used to disable automatic lastModified parameters.
static final String	LAST_MODIFIED_PARAMETER_NAME	The name of the last modified parameter that is optionally added.

Constructor Summary

Constructors

Constructor	Description
LastModifiedServlet()

Method Summary

Modifier and Type	Method	Description
static String	addLastModified(ServletContext servletContext, HttpServletRequest request, String servletPath, String url, AddLastModified when)	Adds a last modified time (to the nearest second) to a URL if the resource is directly available as a local resource.
protected void	doGet(HttpServletRequest request, HttpServletResponse response)
static String	encodeLastModified(long lastModified)	Encodes a last modified value.
protected long	getLastModified(HttpServletRequest request)
static long	getLastModified(ServletContext servletContext, HttpServletRequest request, String path)	Automatically determines extension from path.
static long	getLastModified(ServletContext servletContext, HttpServletRequest request, String path, String extension)	Gets a last modified time given a context-relative path starting with a slash (/).
void	init(ServletConfig config)

Methods inherited from class javax.servlet.http.HttpServlet

doDelete, doHead, doOptions, doPost, doPut, doTrace, service, service

Methods inherited from class javax.servlet.GenericServlet

destroy, getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, init, log, log

Methods inherited from class java.lang.Object

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

Field Details

DEFAULT_CACHE_CONTROL

public static final String DEFAULT_CACHE_CONTROL

The default, short-term, cache-control header value.

Only used when the cache-control header has not already been set, which will normally already be set to a much more aggressive value by LastModifiedHeaderFilter.

See Also:

• Constant Field Values

LAST_MODIFIED_PARAMETER_NAME

public static final String LAST_MODIFIED_PARAMETER_NAME

The name of the last modified parameter that is optionally added. The value is URL-safe and does not need to be encoded.

See Also:

• Constant Field Values

LAST_MODIFIED_HEADER_NAME

public static final String LAST_MODIFIED_HEADER_NAME

The header that may be used to disable automatic lastModified parameters.

See Also:

• Constant Field Values

Constructor Details

LastModifiedServlet

public LastModifiedServlet()

Method Details

encodeLastModified

public static String encodeLastModified(long lastModified)

Encodes a last modified value. The value is URL-safe and does not need to be encoded.

getLastModified

public static long getLastModified(ServletContext servletContext,
 HttpServletRequest request,
 String path,
 String extension)

Gets a last modified time given a context-relative path starting with a slash (/).

Any file ending in ".css" (case-insensitive) will be parsed and will have a modified time that is equal to the greatest of itself or any referenced URL.

Returns:

the modified time or 0 when unknown.

getLastModified

public static long getLastModified(ServletContext servletContext,
 HttpServletRequest request,
 String path)

Automatically determines extension from path.

See Also:

• getLastModified(javax.servlet.ServletContext, javax.servlet.http.HttpServletRequest, java.lang.String, java.lang.String)

addLastModified

public static String addLastModified(ServletContext servletContext,
 HttpServletRequest request,
 String servletPath,
 String url,
 AddLastModified when)
                              throws MalformedURLException

Adds a last modified time (to the nearest second) to a URL if the resource is directly available as a local resource. Only applies to relative URLs (./, ../) or URLs that begin with a slash (/).

Will not modify when the request has header LAST_MODIFIED_HEADER_NAME equal to "false".

Will not modify Canonical URLs.

Throws:

MalformedURLException

init

public void init(ServletConfig config)
          throws ServletException

Specified by:

init in interface Servlet

Overrides:

init in class GenericServlet

Throws:

ServletException

getLastModified

protected long getLastModified(HttpServletRequest request)

Overrides:

getLastModified in class HttpServlet

doGet

protected void doGet(HttpServletRequest request,
 HttpServletResponse response)
              throws ServletException,
IOException

Overrides:

doGet in class HttpServlet

Throws:

ServletException

IOException