org.springframework.extensions.surf

Class CssImageDataHandler

java.lang.Object

org.springframework.extensions.surf.CssImageDataHandler

All Implemented Interfaces:

CacheReporter

public class CssImageDataHandler
extends Object
implements CacheReporter

This class provides the capability to search through CSS resources and convert all URL references to be Base64 encoded data. This can have performance benefits since as CSS files that include data rather than links will reduce the number of HTTP requests that the browser needs to make. Processing CSS resources in this way will only be enabled if the Surf application configuration sets the property <generate-css-data-images> to true (however, is will only have an effect if the property use-checksum-dependencies> is also set to true.

Author:

David Draper

Field Summary

Fields

Modifier and Type	Field and Description
static String	DATA_BASE64_ENCODING This is the second part of the CSS data image text.
static String	DATA_IMAGE_PREFIX This is the first part of the CSS data image text.
static String	DOUBLE_FULL_STOP Constant for double full stop ".." (or period as it is known in the US).
static String	DOUBLE_FULL_STOP_SLASH
static String	DOUBLE_QUOTES Constant for the double quote '"'.
static String	FORWARD_SLASH Constant for the forward slash "/"
static String	FULL_STOP Constant for the full stop "." (or period as it is known in the US).
static String	MISSING_IMAGE_SENTINENEL The empty String is used as the missing image sentinel.
static String	SINGLE_QUOTE Constant for the single quote "'"
protected ThreadLocal<byte[]>	streamBuffer Thread local stream byte buffer.
static String	URL_CLOSE_TARGET_PATTERN This is the String used to target the end of an image URL.
static String	URL_OPEN_TARGET_PATTERN This is the String used to target the start of image URL.

Constructor Summary

Constructors

Constructor and Description
CssImageDataHandler()

Method Summary

Methods

Modifier and Type	Method and Description
void	clearCaches()
protected String	encodeImage(InputStream in) Converts the image file in the supplied InputStream into a Base64 encoded String.
DependencyHandler	getDependencyHandler()
String	getEncodedImage(String path) Gets the encoded image for the supplied path.
List<String>	getExcludeCssPaths()
List<String>	getExcludeMimeTypes()
protected List<Pattern>	getExcludePatterns()
Integer	getMaximumImageSize() Gets the maximum image size to allow to be encoded
Map<String,String>	getRemapMimetypes()
int	insert(StringBuilder toUpdate, int offset, String toInsert) Helper method for inserting content into a StringBuilder whilst maintaining a reference to the offset that indicates the end of the inserted content.
void	processCssImages(String cssPath, StringBuilder cssContents) Updates the supplied StringBuilder (which should contain the contents of a CSS file) so that all image URLs are converted into Base64 encoded data.
List<CacheReport>	report()
void	setDependencyHandler(DependencyHandler dependencyHandler) Setter provided to allow the Spring application context to set the DependencyHandler.
void	setExcludeCssPaths(List<String> excludeCssPaths)
void	setExcludeMimeTypes(List<String> excludeMimeTypes)
void	setMaximumImageSize(Integer maximumImageSize) This setter is provided to allow the Spring application context to set the maximum size of image to encode (in bytes).
void	setRemapMimetypes(Map<String,String> remapMimetypes)

Methods inherited from class java.lang.Object

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

Field Detail

DATA_IMAGE_PREFIX

public static final String DATA_IMAGE_PREFIX

This is the first part of the CSS data image text. This is the text that runs up until the MIME type of the image.

See Also:

Constant Field Values

DATA_BASE64_ENCODING

public static final String DATA_BASE64_ENCODING

This is the second part of the CSS data image text. It runs from the MIME type to Base64 encoded data.

See Also:

Constant Field Values

URL_OPEN_TARGET_PATTERN

public static final String URL_OPEN_TARGET_PATTERN

This is the String used to target the start of image URL. NOTE: At the moment this assumes URL only applies to "background-image" which is technically not guaranteed in the specification.

See Also:

Constant Field Values

URL_CLOSE_TARGET_PATTERN

public static final String URL_CLOSE_TARGET_PATTERN

This is the String used to target the end of an image URL. The first occurrence of the closing bracket after the opening bracket should mark the end of the URL because it is not valid as part of a URL.

See Also:

Constant Field Values

FORWARD_SLASH

public static final String FORWARD_SLASH

Constant for the forward slash "/"

See Also:

Constant Field Values

FULL_STOP

public static final String FULL_STOP

Constant for the full stop "." (or period as it is known in the US). In this context it is used to indicate the current location in paths.

See Also:

Constant Field Values

DOUBLE_FULL_STOP

public static final String DOUBLE_FULL_STOP

Constant for double full stop ".." (or period as it is known in the US). In this context it is used to indicate the part folder of the current location.

See Also:

Constant Field Values

DOUBLE_QUOTES

public static final String DOUBLE_QUOTES

Constant for the double quote '"'.

See Also:

Constant Field Values

SINGLE_QUOTE

public static final String SINGLE_QUOTE

Constant for the single quote "'"

See Also:

Constant Field Values

DOUBLE_FULL_STOP_SLASH

public static final String DOUBLE_FULL_STOP_SLASH

See Also:

Constant Field Values

MISSING_IMAGE_SENTINENEL

public static final String MISSING_IMAGE_SENTINENEL

The empty String is used as the missing image sentinel. We cannot use null as this will indicate that that the encoded image does not exist in the cache. However the empty String can be used as no image will ever be encoded to the empty String as it MUST contain some data.

See Also:

Constant Field Values

streamBuffer

protected ThreadLocal<byte[]> streamBuffer

Thread local stream byte buffer.

Constructor Detail

CssImageDataHandler

public CssImageDataHandler()

Method Detail

getMaximumImageSize

public Integer getMaximumImageSize()

Gets the maximum image size to allow to be encoded

Returns:

Integer

setMaximumImageSize

public void setMaximumImageSize(Integer maximumImageSize)

This setter is provided to allow the Spring application context to set the maximum size of image to encode (in bytes).

Parameters:

maximumImageSize - The maximum size of an image to encode (in bytes)

getDependencyHandler

public DependencyHandler getDependencyHandler()

setDependencyHandler

public void setDependencyHandler(DependencyHandler dependencyHandler)

Setter provided to allow the Spring application context to set the DependencyHandler.

Parameters:

dependencyHandler - DependencyHandler

getRemapMimetypes

public Map<String,String> getRemapMimetypes()

setRemapMimetypes

public void setRemapMimetypes(Map<String,String> remapMimetypes)

getExcludeMimeTypes

public List<String> getExcludeMimeTypes()

setExcludeMimeTypes

public void setExcludeMimeTypes(List<String> excludeMimeTypes)

getExcludeCssPaths

public List<String> getExcludeCssPaths()

setExcludeCssPaths

public void setExcludeCssPaths(List<String> excludeCssPaths)

getExcludePatterns

protected List<Pattern> getExcludePatterns()

processCssImages

public void processCssImages(String cssPath,
                    StringBuilder cssContents)
                      throws IOException

Updates the supplied StringBuilder (which should contain the contents of a CSS file) so that all image URLs are converted into Base64 encoded data. This method uses the DependencyHandler to load the image file and if the image cannot be loaded then it will not be encoded and will be left as the original URL.

Parameters:

cssPath - The path the CSS file.

cssContents - The contents of the CSS file.

Throws:

IOException

insert

public int insert(StringBuilder toUpdate,
         int offset,
         String toInsert)

Helper method for inserting content into a StringBuilder whilst maintaining a reference to the offset that indicates the end of the inserted content.

Parameters:

toUpdate - The StringBuilder to update.

offset - The current offset (e.g. where to insert the supplied String)

toInsert - The String to insert.

Returns:

A new offset that indicates the end of the inserted String within the StringBuilder.

getEncodedImage

public String getEncodedImage(String path)

Gets the encoded image for the supplied path. This method will first check the private cache to see if the image has previously been encoded and if it cannot be found then it will attempt to load the image and encode it. If the image resource could not be loaded then this method will return null

Parameters:

path - The path to the image to get the encoded String representation.

Returns:

A Base64 encoded String representing the image or null if the image could not be loaded.

encodeImage

protected String encodeImage(InputStream in)
                      throws IOException

Converts the image file in the supplied InputStream into a Base64 encoded String.

Parameters:

in - An InputStream of the image to convert.

Throws:

IOException

clearCaches

public void clearCaches()

Specified by:

clearCaches in interface CacheReporter

report

public List<CacheReport> report()

Specified by:

report in interface CacheReporter